What rays does the sun emit? Causes of solar radiation

The Earth receives from the Sun 1.36 * 10v24 cal of heat per year. Compared to this amount of energy, the remaining amount of radiant energy reaching the Earth's surface is negligible. Thus, the radiant energy of the stars is one hundred millionth of the solar energy, cosmic radiation is two billionths, the internal heat of the Earth at its surface is equal to one five thousandth of the solar heat.
Radiation of the Sun - solar radiation- is the main source of energy for almost all processes occurring in the atmosphere, hydrosphere and in upper layers lithosphere.
Per unit of intensity solar radiation take the number of calories of heat absorbed by 1 cm2 of an absolutely black surface perpendicular to the direction of sunlight in 1 minute (cal / cm2 * min).

The flux of radiant energy from the Sun, reaching earth's atmosphere, is very stable. Its intensity is called the solar constant (Io) and is taken on average to be 1.88 kcal/cm2 min.
The value of the solar constant fluctuates depending on the distance of the Earth from the Sun and on solar activity. Its fluctuations during the year are 3.4-3.5%.
If Sun rays everywhere fell vertically to the earth's surface, then in the absence of an atmosphere and at a solar constant of 1.88 cal / cm2 * min, each square centimeter it would receive 1000 kcal per year. Due to the fact that the Earth is spherical, this amount is reduced by 4 times, and 1 sq. cm receives an average of 250 kcal per year.
The amount of solar radiation received by the surface depends on the angle of incidence of the rays.
The maximum amount of radiation is received by the surface perpendicular to the direction of the sun's rays, because in this case all the energy is distributed to the area with a cross section equal to the cross section of the beam of rays - a. With oblique incidence of the same beam of rays, the energy is distributed over large area(section c) and a unit of surface receives a smaller amount of it. The smaller the angle of incidence of the rays, the lower the intensity of solar radiation.
The dependence of the intensity of solar radiation on the angle of incidence of rays is expressed by the formula:

I1 = I0 * sinh,

where I0 is the intensity of solar radiation at a sheer incidence of rays. Outside the atmosphere, the solar constant;
I1 - the intensity of solar radiation when the sun's rays fall at an angle h.
I1 is as many times less than I0, how many times the section a is less than the section b.
Figure 27 shows that a / b \u003d sin A.
The angle of incidence of the sun's rays (the height of the Sun) is equal to 90 ° only at latitudes from 23 ° 27 "N to 23 ° 27" S. (i.e. between the tropics). At other latitudes, it is always less than 90° (Table 8). According to the decrease in the angle of incidence of rays, the intensity of solar radiation arriving at the surface at different latitudes should also decrease. Since the height of the Sun does not remain constant throughout the year and during the day, the amount of solar heat received by the surface changes continuously.

The amount of solar radiation received by the surface is directly related to from the duration of its exposure to sunlight.

In the equatorial zone outside the atmosphere, the amount of solar heat during the year does not experience large fluctuations, while at high latitudes these fluctuations are very large (see Table 9). AT winter period differences in solar heat gain between high and low latitudes are especially significant. AT summer period, in conditions of continuous illumination, the polar regions receive the maximum amount of solar heat per day on Earth. On the day of the summer solstice in the northern hemisphere, it is 36% higher than the daily amount of heat at the equator. But since the duration of the day at the equator is not 24 hours (as at this time at the pole), but 12 hours, the amount of solar radiation per unit of time at the equator remains the largest. Summer high daily amount solar heat, observed at about 40-50° latitude, is associated with a relatively long duration of the day (greater than at this time by 10-20° latitude) at considerable height Sun. Differences in the amount of heat received by the equatorial and polar regions are smaller in summer than in winter.
The southern hemisphere receives more heat in summer than the northern one, and vice versa in winter (it is affected by the change in the distance of the Earth from the Sun). And if the surface of both hemispheres were completely homogeneous, the annual amplitudes of temperature fluctuations in the southern hemisphere would be greater than in the northern.
Solar radiation in the atmosphere undergoes quantitative and qualitative changes.
Even an ideal, dry and clean atmosphere absorbs and scatters rays, reducing the intensity of solar radiation. The weakening effect of the real atmosphere, containing water vapor and solid impurities, on solar radiation is much greater than the ideal one. The atmosphere (oxygen, ozone, carbon dioxide, dust and water vapor) absorbs mainly ultraviolet and infrared rays. The radiant energy of the Sun absorbed by the atmosphere is converted into other types of energy: thermal, chemical, etc. In general, absorption weakens solar radiation by 17-25%.
Molecules of atmospheric gases scatter rays with relatively short waves - violet, blue. This is what explains the blue color of the sky. Impurities equally scatter rays with waves of different wavelengths. Therefore, with a significant content of them, the sky acquires a whitish tint.
Due to the scattering and reflection of the sun's rays by the atmosphere, daylight is observed on cloudy days, objects in the shade are visible, and the phenomenon of twilight occurs.
The longer the path of the beam in the atmosphere, the greater its thickness it must pass and the more significantly the solar radiation is attenuated. Therefore, with elevation, the influence of the atmosphere on radiation decreases. The length of the path of sunlight in the atmosphere depends on the height of the Sun. If we take as a unit the length of the path of the solar beam in the atmosphere at the height of the Sun 90 ° (m), the ratio between the height of the Sun and the path length of the beam in the atmosphere will be as shown in Table. ten.

The total attenuation of radiation in the atmosphere at any height of the Sun can be expressed by the Bouguer formula: Im = I0 * pm, where Im is the intensity of solar radiation near the earth's surface changed in the atmosphere; I0 - solar constant; m is the path of the beam in the atmosphere; at a solar height of 90 ° it is equal to 1 (the mass of the atmosphere), p is the transparency coefficient (a fractional number showing what fraction of radiation reaches the surface at m = 1).
At a height of the Sun of 90°, at m=1, the intensity of solar radiation near the earth's surface I1 is p times less than Io, i.e. I1=Io*p.
If the height of the Sun is less than 90°, then m is always greater than 1. The path of a solar ray can consist of several segments, each of which is equal to 1. The intensity of solar radiation at the border between the first (aa1) and second (a1a2) segments I1 is obviously equal to Io *p, radiation intensity after passing the second segment I2=I1*p=I0 p*p=I0 p2; I3=I0p3 etc.

The transparency of the atmosphere is not constant and is not the same in various conditions. The ratio of the transparency of the real atmosphere to the transparency of the ideal atmosphere - the turbidity factor - is always more than one. It depends on the content of water vapor and dust in the air. With an increase in geographical latitude, the turbidity factor decreases: at latitudes from 0 to 20 ° N. sh. it is equal to 4.6 on average, at latitudes from 40 to 50 ° N. sh. - 3.5, at latitudes from 50 to 60 ° N. sh. - 2.8 and at latitudes from 60 to 80 ° N. sh. - 2.0. AT temperate latitudes the turbidity factor is lower in winter than in summer, and lower in the morning than in the afternoon. It decreases with height. The greater the turbidity factor, the greater the attenuation of solar radiation.
Distinguish direct, diffuse and total solar radiation.
Part of the solar radiation that penetrates through the atmosphere to the earth's surface is direct radiation. Part of the radiation scattered by the atmosphere is converted into diffuse radiation. All solar radiation entering the earth's surface, direct and diffuse, is called total radiation.
The ratio between direct and scattered radiation varies considerably depending on the cloudiness, dustiness of the atmosphere, and also on the height of the Sun. At clear sky the proportion of scattered radiation does not exceed 0.1%; in a cloudy sky, diffuse radiation can be greater than direct radiation.
At a low altitude of the Sun, the total radiation consists almost entirely of scattered radiation. At a solar altitude of 50° and a clear sky, the fraction of scattered radiation does not exceed 10-20%.
Maps of average annual and monthly values ​​of total radiation make it possible to notice the main patterns in its geographical distribution. The annual values ​​of total radiation are distributed mainly zonal. The largest annual amount of total radiation on Earth is received by the surface in tropical inland deserts (Eastern Sahara and the central part of Arabia). A noticeable decrease in total radiation at the equator is caused by high air humidity and high cloudiness. In the Arctic, the total radiation is 60-70 kcal/cm2 per year; in the Antarctic, due to the frequent recurrence of clear days and the greater transparency of the atmosphere, it is somewhat greater.

In June, the northern hemisphere receives the largest amounts of radiation, and especially the inland tropical and subtropical regions. The amounts of solar radiation received by the surface in the temperate and polar latitudes of the northern hemisphere differ little, owing mainly to the long duration of the day in the polar regions. Zoning in the distribution of total radiation above. continents in the northern hemisphere and in the tropical latitudes of the southern hemisphere is almost not expressed. It is better manifested in the northern hemisphere over the Ocean and is clearly expressed in the extratropical latitudes of the southern hemisphere. At the southern polar circle, the value of total solar radiation approaches 0.
In December, the largest amounts of radiation enter the southern hemisphere. The high-lying ice surface of Antarctica, with high air transparency, receives significantly more total radiation than the surface of the Arctic in June. There is a lot of heat in the deserts (Kalahari, Great Australian), but due to the greater oceanicity of the southern hemisphere (influence high humidity air and cloudiness) its total here is somewhat less than in June at the same latitudes of the northern hemisphere. In the equatorial and tropical latitudes of the northern hemisphere, the total radiation varies relatively little, and the zoning in its distribution is clearly expressed only to the north of the northern tropic. With increasing latitude, the total radiation decreases rather rapidly; its zero isoline passes somewhat north of the Arctic Circle.
The total solar radiation, falling on the Earth's surface, is partially reflected back into the atmosphere. The ratio of the amount of radiation reflected from a surface to the amount of radiation incident on that surface is called albedo. Albedo characterizes the reflectivity of a surface.
The albedo of the earth's surface depends on its condition and properties: color, humidity, roughness, etc. Freshly fallen snow has the highest reflectivity (85-95%). A calm water surface reflects only 2-5% of the sun's rays when it falls vertically, and almost all the rays falling on it (90%) when the sun is low. Albedo of dry chernozem - 14%, wet - 8, forest - 10-20, meadow vegetation - 18-30, sandy desert surfaces - 29-35, surfaces sea ​​ice - 30-40%.
The large albedo of the ice surface, especially when covered with fresh snow (up to 95%), is the reason for low temperatures in the polar regions in summer, when the arrival of solar radiation is significant there.
Radiation of the earth's surface and atmosphere. Any body with a temperature above absolute zero(greater than minus 273°), emits radiant energy. The total emissivity of a blackbody is proportional to the fourth power of its absolute temperature (T):
E \u003d σ * T4 kcal / cm2 per minute (Stefan-Boltzmann law), where σ is a constant coefficient.
The higher the temperature of the radiating body, the shorter the wavelength of the emitted nm rays. The incandescent Sun sends into space shortwave radiation. The earth's surface, absorbing short-wave solar radiation, heats up and also becomes a source of radiation (terrestrial radiation). Ho, since the temperature of the earth's surface does not exceed several tens of degrees, its long-wave radiation, invisible.
Earth radiation is largely retained by the atmosphere (water vapor, carbon dioxide, ozone), but rays with a wavelength of 9-12 microns freely go beyond the atmosphere, and therefore the Earth loses some of its heat.
The atmosphere, absorbing part of the solar radiation passing through it and more than half of the earth's, itself radiates energy both into the world space and to the earth's surface. Atmospheric radiation directed towards the earth's surface towards the earth's surface is called opposite radiation. This radiation, like the terrestrial, long-wave, invisible.
Two streams of long-wave radiation meet in the atmosphere - the radiation of the Earth's surface and the radiation of the atmosphere. The difference between them, which determines the actual loss of heat by the earth's surface, is called efficient radiation. Effective radiation is the greater, the higher the temperature of the radiating surface. Air humidity reduces the effective radiation, its clouds greatly reduce it.
The highest value of the annual sums of effective radiation is observed in tropical deserts - 80 kcal / cm2 per year - due to the high surface temperature, dry air and clear sky. At the equator, with high air humidity, the effective radiation is only about 30 kcal/cm2 per year, and its value for land and for the ocean differs very little. The lowest effective radiation in the polar regions. In temperate latitudes, the earth's surface loses about half of the amount of heat that it receives from the absorption of total radiation.
The ability of the atmosphere to pass the short-wave radiation of the Sun (direct and diffuse radiation) and delay the long-wave radiation of the Earth is called the greenhouse (greenhouse) effect. Thanks to the greenhouse effect average temperature the earth's surface is +16°, in the absence of an atmosphere it would be -22° (38° lower).
Radiation balance (residual radiation). The earth's surface simultaneously receives radiation and gives it away. The arrival of radiation is the total solar radiation and the counter radiation of the atmosphere. Consumption - the reflection of sunlight from the surface (albedo) and the own radiation of the earth's surface. The difference between the incoming and outgoing radiation is radiation balance, or residual radiation. The value of the radiation balance is determined by the equation

R \u003d Q * (1-α) - I,

where Q is the total solar radiation per unit surface; α - albedo (fraction); I - effective radiation.
If the input is greater than the output, the radiation balance is positive; if the input is less than the output, the balance is negative. At night, at all latitudes, the radiation balance is negative; during the day, until noon, it is positive everywhere, except for high latitudes in winter; in the afternoon - again negative. On average per day, the radiation balance can be both positive and negative (Table 11).


On the map of the annual sums of the radiation balance of the earth's surface, one can see a sharp change in the position of the isolines when they move from land to the ocean. As a rule, the radiation balance of the Ocean surface exceeds the radiation balance of the land (the effect of albedo and effective radiation). The distribution of the radiation balance is generally zonal. On the Ocean in tropical latitudes, the annual values ​​of the radiation balance reach 140 kcal/cm2 (Arabian Sea) and do not exceed 30 kcal/cm2 at the boundary of floating ice. Deviations from the zonal distribution of the radiation balance in the Ocean are insignificant and are caused by the distribution of clouds.
On land in the equatorial and tropical latitudes, the annual values ​​of the radiation balance vary from 60 to 90 kcal/cm2, depending on the moisture conditions. The largest annual sums of the radiation balance are noted in those areas where the albedo and effective radiation are relatively small (moist tropical forests, savannahs). Their lowest value is in very humid (large cloudiness) and in very dry (large effective radiation) areas. In temperate and high latitudes, the annual value of the radiation balance decreases with increasing latitude (the effect of a decrease in total radiation).
The annual sums of the radiation balance over the central regions of Antarctica are negative (several calories per 1 cm2). In the Arctic, these values ​​are close to zero.
In July, the radiation balance of the earth's surface in a significant part of the southern hemisphere is negative. Line zero balance passes between 40 and 50° S. sh. highest value the values ​​of the radiation balance reach on the surface of the Ocean in the tropical latitudes of the northern hemisphere and on the surface of some inland seas, for example Black (14-16 kcal / cm2 per month).
In January, the zero balance line is located between 40 and 50°N. sh. (over the oceans it rises somewhat to the north, over the continents it descends to the south). A significant part of the northern hemisphere has a negative radiation balance. The largest values ​​of the radiation balance are confined to the tropical latitudes of the southern hemisphere.
On average for the year, the radiation balance of the earth's surface is positive. In this case, the surface temperature does not increase, but remains approximately constant, which can only be explained by the continuous consumption of excess heat.
The radiation balance of the atmosphere consists of the solar and terrestrial radiation absorbed by it, on the one hand, and atmospheric radiation, on the other. It is always negative, since the atmosphere absorbs only a small part of solar radiation, and radiates almost as much as the surface.
The radiation balance of the surface and the atmosphere together, as a whole, for the entire Earth for a year is equal to zero on average, but in latitudes it can be both positive and negative.
The consequence of such a distribution of the radiation balance should be the transfer of heat in the direction from the equator to the poles.
Thermal balance. Radiation balance is the most important component heat balance. The surface heat balance equation shows how the incoming solar radiation energy is converted on the earth's surface:

where R is the radiation balance; LE - heat consumption for evaporation (L - latent heat of vaporization, E - evaporation);
P - turbulent heat exchange between the surface and the atmosphere;
A - heat exchange between the surface and underlying layers of soil or water.
The radiation balance of a surface is considered positive if the radiation absorbed by the surface exceeds the heat loss, and negative if it does not replenish them. All other terms of the heat balance are considered positive if they cause heat loss by the surface (if they correspond to heat consumption). Because. all terms of the equation can change, the heat balance is constantly disturbed and restored again.
The equation of the heat balance of the surface considered above is approximate, since it does not take into account some secondary, but under specific conditions, factors that become important, for example, the release of heat during freezing, its consumption for thawing, etc.
The heat balance of the atmosphere consists of the radiation balance of the atmosphere Ra, the heat coming from the surface, Pa, the heat released in the atmosphere during condensation, LE, and the horizontal heat transfer (advection) Aa. The radiation balance of the atmosphere is always negative. The influx of heat as a result of moisture condensation and the magnitude of turbulent heat transfer are positive. Heat advection leads, on average per year, to its transfer from low latitudes to high latitudes: thus, it means heat consumption at low latitudes and arrival at high latitudes. In a multi-year derivation, the heat balance of the atmosphere can be expressed by the equation Ra=Pa+LE.
The heat balance of the surface and the atmosphere together as a whole is equal to 0 on a long-term average (Fig. 35).

The amount of solar radiation entering the atmosphere per year (250 kcal/cm2) is taken as 100%. Solar radiation, penetrating into the atmosphere, is partially reflected from the clouds and goes back beyond the atmosphere - 38%, partially absorbed by the atmosphere - 14%, and partially in the form of direct solar radiation reaches the earth's surface - 48%. Of the 48% that reach the surface, 44% are absorbed by it, and 4% are reflected. Thus, the Earth's albedo is 42% (38+4).
The radiation absorbed by the earth's surface is spent as follows: 20% is lost through effective radiation, 18% is spent on evaporation from the surface, 6% is spent on heating the air during turbulent heat transfer (total 24%). The loss of heat by the surface balances its arrival. The heat received by the atmosphere (14% directly from the Sun, 24% from the earth's surface), together with the effective radiation of the Earth, is directed into the world space. The Earth's albedo (42%) and radiation (58%) balance the influx of solar radiation to the atmosphere.

Heat sources. In the life of the atmosphere crucial has thermal energy. The main source of this energy is the Sun. As for the thermal radiation of the Moon, planets and stars, it is so negligible for the Earth that in practice it cannot be taken into account. Much more thermal energy is provided by the internal heat of the Earth. According to the calculations of geophysicists, a constant influx of heat from the bowels of the Earth increases the temperature of the earth's surface by 0.1. But such an influx of heat is still so small that there is no need to take it into account either. Thus, only the Sun can be considered the only source of thermal energy on the Earth's surface.

Solar radiation. The sun, which has a temperature of the photosphere (radiating surface) of about 6000°, radiates energy into space in all directions. Part of this energy in the form of a huge beam of parallel solar rays hits the Earth. Solar energy that reaches the earth's surface in the form of direct rays from the sun is called direct solar radiation. But not all solar radiation directed to the Earth reaches the earth's surface, since the sun's rays, passing through a powerful layer of the atmosphere, are partially absorbed by it, partially scattered by molecules and suspended particles of air, some of it is reflected by clouds. The portion of solar energy that is dissipated in the atmosphere is called scattered radiation. Scattered solar radiation propagates in the atmosphere and reaches the Earth's surface. We perceive this type of radiation as uniform daylight when the Sun is completely covered by clouds or has just disappeared below the horizon.

Direct and diffuse solar radiation, reaching the Earth's surface, is not completely absorbed by it. Part of the solar radiation is reflected from the earth's surface back into the atmosphere and is there in the form of a stream of rays, the so-called reflected solar radiation.

The composition of solar radiation is very complex, which is associated with a very high temperature of the radiating surface of the Sun. Conventionally, according to the wavelength, the spectrum of solar radiation is divided into three parts: ultraviolet (η<0,4<μ видимую глазом (η from 0.4μ to 0.76μ) and infrared (η >0.76μ). In addition to the temperature of the solar photosphere, the composition of solar radiation near the earth's surface is also influenced by the absorption and scattering of part of the sun's rays as they pass through the air envelope of the Earth. In this regard, the composition of solar radiation at the upper boundary of the atmosphere and near the Earth's surface will be different. Based on theoretical calculations and observations, it has been established that at the boundary of the atmosphere, ultraviolet radiation accounts for 5%, visible rays - 52% and infrared - 43%. At the earth's surface (at a Sun height of 40 °), ultraviolet rays make up only 1%, visible - 40%, and infrared - 59%.

Intensity of solar radiation. Under the intensity of direct solar radiation understand the amount of heat in calories received in 1 minute. from the radiant energy of the Sun by the surface in 1 cm 2, placed perpendicular to the sun.

To measure the intensity of direct solar radiation, special instruments are used - actinometers and pyrheliometers; the amount of scattered radiation is determined by a pyranometer. Automatic recording of the duration of solar radiation action is carried out by actinographs and heliographs. The spectral intensity of solar radiation is determined by a spectrobolograph.

At the boundary of the atmosphere, where the absorbing and scattering effects of the Earth's air envelope are excluded, the intensity of direct solar radiation is approximately 2 feces for 1 cm 2 surfaces in 1 min. This value is called solar constant. The intensity of solar radiation in 2 feces for 1 cm 2 in 1 min. gives such a large amount of heat during the year that it would be enough to melt a layer of ice 35 m thick, if such a layer covered the entire earth's surface.

Numerous measurements of the intensity of solar radiation give reason to believe that the amount of solar energy coming to the upper boundary of the Earth's atmosphere experiences fluctuations in the amount of several percent. Oscillations are periodic and non-periodic, apparently associated with the processes occurring on the Sun itself.

In addition, some change in the intensity of solar radiation occurs during the year due to the fact that the Earth in its annual rotation does not move in a circle, but in an ellipse, in one of the foci of which is the Sun. In this regard, the distance from the Earth to the Sun changes and, consequently, there is a fluctuation in the intensity of solar radiation. The greatest intensity is observed around January 3, when the Earth is closest to the Sun, and the smallest around July 5, when the Earth is at its maximum distance from the Sun.

For this reason, the fluctuation in the intensity of solar radiation is very small and can only be of theoretical interest. (The amount of energy at maximum distance is related to the amount of energy at minimum distance, as 100:107, i.e. the difference is completely negligible.)

Conditions for irradiation of the surface of the globe. Already the spherical shape of the Earth alone leads to the fact that the radiant energy of the Sun is distributed very unevenly on the earth's surface. So, on the days of the spring and autumn equinoxes (March 21 and September 23), only at the equator at noon, the angle of incidence of the rays will be 90 ° (Fig. 30), and as it approaches the poles, it will decrease from 90 to 0 °. In this way,

if at the equator the amount of radiation received is taken as 1, then at the 60th parallel it will be expressed as 0.5, and at the pole it will be equal to 0.

The globe, in addition, has a daily and annual movement, and the earth's axis is inclined to the plane of the orbit by 66 °.5. Due to this inclination, an angle of 23 ° 30 g is formed between the plane of the equator and the plane of the orbit. This circumstance leads to the fact that the angles of incidence of the sun's rays for the same latitudes will vary within 47 ° (23.5 + 23.5) .

Depending on the time of year, not only the angle of incidence of the rays changes, but also the duration of illumination. If in tropical countries at all times of the year the duration of day and night is approximately the same, then in polar countries, on the contrary, it is very different. For example, at 70° N. sh. in summer, the Sun does not set for 65 days, at 80 ° N. sh.- 134, and at the pole -186. Because of this, at the North Pole, radiation on the day of the summer solstice (June 22) is 36% more than at the equator. As for the entire summer half-year, the total amount of heat and light received by the pole is only 17% less than at the equator. Thus, in the summertime in polar countries, the duration of illumination largely compensates for the lack of radiation, which is a consequence of the small angle of incidence of the rays. In the winter half of the year, the picture is completely different: the amount of radiation at the same North Pole will be 0. As a result, the average amount of radiation at the pole is 2.4 times less than at the equator. From all that has been said, it follows that the amount of solar energy that the Earth receives by radiation is determined by the angle of incidence of the rays and the duration of exposure.

In the absence of an atmosphere at different latitudes, the earth's surface would receive the following amount of heat per day, expressed in calories per 1 cm 2(see table on page 92).

The distribution of radiation over the earth's surface given in the table is commonly called solar climate. We repeat that we have such a distribution of radiation only at the upper boundary of the atmosphere.

Attenuation of solar radiation in the atmosphere. So far, we have been talking about the conditions for the distribution of solar heat over the earth's surface, without taking into account the atmosphere. Meanwhile, the atmosphere in this case is of great importance. Solar radiation, passing through the atmosphere, experiences dispersion and, in addition, absorption. Both of these processes together attenuate solar radiation to a large extent.

The sun's rays, passing through the atmosphere, first of all experience scattering (diffusion). Scattering is created by the fact that the rays of light, refracting and reflecting from air molecules and particles of solid and liquid bodies in the air, deviate from the direct path to really "spread out".

Scattering greatly attenuates solar radiation. With an increase in the amount of water vapor and especially dust particles, the dispersion increases and the radiation is weakened. In large cities and desert areas, where the dust content of the air is greatest, dispersion weakens the strength of radiation by 30-45%. Thanks to scattering, the daylight is obtained, which illuminates objects, even if the sun's rays do not fall directly on them. Scattering determines the very color of the sky.

Let us now dwell on the ability of the atmosphere to absorb the radiant energy of the Sun. The main gases that make up the atmosphere absorb radiant energy relatively very little. Impurities (water vapor, ozone, carbon dioxide and dust), on the contrary, are distinguished by a high absorption capacity.

In the troposphere, the most significant admixture is water vapor. They absorb especially strongly infrared (long-wave), i.e., predominantly thermal rays. And the more water vapor in the atmosphere, the naturally more and. absorption. The amount of water vapor in the atmosphere is subject to large changes. Under natural conditions, it varies from 0.01 to 4% (by volume).

Ozone is very absorbent. A significant admixture of ozone, as already mentioned, is in the lower layers of the stratosphere (above the tropopause). Ozone absorbs ultraviolet (shortwave) rays almost completely.

Carbon dioxide is also very absorbent. It absorbs mainly long-wave, i.e., predominantly thermal rays.

Dust in the air also absorbs some of the sun's radiation. Heating up under the action of sunlight, it can significantly increase the temperature of the air.

Of the total amount of solar energy coming to Earth, the atmosphere absorbs only about 15%.

The attenuation of solar radiation by scattering and absorption by the atmosphere is very different for different latitudes of the Earth. This difference depends primarily on the angle of incidence of the rays. At the zenith position of the Sun, the rays, falling vertically, cross the atmosphere in the shortest way. As the angle of incidence decreases, the path of the rays lengthens and the attenuation of solar radiation becomes more significant. The latter is clearly seen from the drawing (Fig. 31) and the attached table (in the table, the path of the sun's beam at the zenith position of the Sun is taken as unity).

Depending on the angle of incidence of the rays, not only the number of rays changes, but also their quality. During the period when the Sun is at its zenith (overhead), ultraviolet rays account for 4%,

visible - 44% and infrared - 52%. At the position of the Sun, there are no ultraviolet rays at all at the horizon, visible 28% and infrared 72%.

The complexity of the influence of the atmosphere on solar radiation is aggravated by the fact that its transmission capacity varies greatly depending on the time of year and weather conditions. So, if the sky remained cloudless all the time, then the annual course of the influx of solar radiation at different latitudes could be graphically expressed as follows (Fig. 32) It is clearly seen from the drawing that with a cloudless sky in Moscow in May, June and July solar radiation would produce more than at the equator. Similarly, in the second half of May, in June and the first half of July, more heat would be generated at the North Pole than at the equator and in Moscow. We repeat that this would be the case with a cloudless sky. But in fact, this does not work, because cloud cover significantly weakens solar radiation. Let us give an example shown in the graph (Fig. 33). The graph shows how much solar radiation does not reach the Earth's surface: a significant part of it is retained by the atmosphere and clouds.

However, it must be said that the heat absorbed by the clouds partly goes to warm the atmosphere, and partly indirectly reaches the earth's surface.

The daily and annual course of the intensity of solnight radiation. The intensity of direct solar radiation near the Earth's surface depends on the height of the Sun above the horizon and on the state of the atmosphere (on its dustiness). If. the transparency of the atmosphere during the day was constant, then the maximum intensity of solar radiation would be observed at noon, and the minimum - at sunrise and sunset. In this case, the graph of the course of the daily intensity of solar radiation would be symmetrical with respect to half a day.

The content of dust, water vapor and other impurities in the atmosphere is constantly changing. In this regard, the transparency of the air changes and the symmetry of the graph of the course of the intensity of solar radiation is violated. Often, especially in the summer, at midday, when the earth's surface is heated intensely, powerful ascending air currents occur, and the amount of water vapor and dust in the atmosphere increases. This leads to a significant decrease in solar radiation at noon; the maximum intensity of radiation in this case is observed in the pre-noon or afternoon hours. The annual course of the intensity of solar radiation is also associated with changes in the height of the Sun above the horizon during the year and with the state of transparency of the atmosphere in different seasons. In the countries of the northern hemisphere, the greatest height of the Sun above the horizon occurs in the month of June. But at the same time, the greatest dustiness of the atmosphere is also observed. Therefore, the maximum intensity usually occurs not in the middle of summer, but in the spring months, when the Sun rises quite high * above the horizon, and the atmosphere after winter remains relatively clean. To illustrate the annual course of the solar radiation intensity in the northern hemisphere, we present data on the average monthly midday values ​​of the radiation intensity in Pavlovsk.

The amount of heat from solar radiation. The surface of the Earth during the day continuously receives heat from direct and diffuse solar radiation or only from diffuse radiation (in cloudy weather). The daily value of heat is determined on the basis of actinometric observations: by taking into account the amount of direct and diffuse radiation that has entered the earth's surface. Having determined the amount of heat for each day, the amount of heat received by the earth's surface per month or per year is also calculated.

The daily amount of heat received by the earth's surface from solar radiation depends on the intensity of radiation and on the duration of its action during the day. In this regard, the minimum influx of heat occurs in the winter, and the maximum in the summer. In the geographic distribution of total radiation over the globe, its increase is observed with a decrease in the latitude of the area. This position is confirmed by the following table.

The role of direct and diffuse radiation in the annual amount of heat received by the earth's surface at different latitudes of the globe is not the same. At high latitudes, diffuse radiation predominates in the annual heat sum. With a decrease in latitude, the predominant value passes to direct solar radiation. So, for example, in the Tikhaya Bay, diffuse solar radiation provides 70% of the annual amount of heat, and direct radiation only 30%. In Tashkent, on the contrary, direct solar radiation gives 70%, diffused only 30%.

Reflectivity of the Earth. Albedo. As already mentioned, the Earth's surface absorbs only part of the solar energy coming to it in the form of direct and diffuse radiation. The other part is reflected into the atmosphere. The ratio of the amount of solar radiation reflected by a given surface to the amount of radiant energy flux incident on this surface is called albedo. Albedo is expressed as a percentage and characterizes the reflectivity of a given area of ​​the surface.

Albedo depends on the nature of the surface (properties of the soil, the presence of snow, vegetation, water, etc.) and on the angle of incidence of the Sun's rays on the Earth's surface. So, for example, if the rays fall on the earth's surface at an angle of 45 °, then:

From the above examples, it can be seen that the reflectivity of various objects is not the same. It is most near snow and least near water. However, the examples we have taken refer only to those cases where the height of the Sun above the horizon is 45°. As this angle decreases, the reflectivity increases. So, for example, at a height of the Sun at 90 °, water reflects only 2%, at 50 ° - 4%, at 20 ° -12%, at 5 ° - 35-70% (depending on the state of the water surface).

On average, with a cloudless sky, the surface of the globe reflects 8% of solar radiation. In addition, 9% reflects the atmosphere. Thus, the globe as a whole, with a cloudless sky, reflects 17% of the radiant energy of the Sun falling on it. If the sky is covered with clouds, then 78% of the radiation is reflected from them. If we take natural conditions, based on the ratio between a cloudless sky and a sky covered with clouds, which is observed in reality, then the reflectivity of the Earth as a whole is 43%.

Terrestrial and atmospheric radiation. The earth, receiving solar energy, heats up and itself becomes a source of heat radiation into the world space. However, the rays emitted by the earth's surface differ sharply from the sun's rays. The earth emits only long-wave (λ 8-14 μ) invisible infrared (thermal) rays. The energy emitted by the earth's surface is called earth radiation. Earth radiation occurs and. day and night. The intensity of the radiation is greater, the higher the temperature of the radiating body. Terrestrial radiation is determined in the same units as solar radiation, i.e., in calories from 1 cm 2 surfaces in 1 min. Observations have shown that the magnitude of terrestrial radiation is small. Usually it reaches 15-18 hundredths of a calorie. But, acting continuously, it can give a significant thermal effect.

The strongest terrestrial radiation is obtained with a cloudless sky and good transparency of the atmosphere. Cloudiness (especially low clouds) significantly reduces terrestrial radiation and often brings it to zero. Here we can say that the atmosphere, together with the clouds, is a good "blanket" that protects the Earth from excessive cooling. Parts of the atmosphere, like areas of the earth's surface, radiate energy according to their temperature. This energy is called atmospheric radiation. The intensity of atmospheric radiation depends on the temperature of the radiating part of the atmosphere, as well as on the amount of water vapor and carbon dioxide contained in the air. Atmospheric radiation belongs to the group of long-wave radiation. It spreads in the atmosphere in all directions; some of it reaches the earth's surface and is absorbed by it, the other part goes into interplanetary space.

O income and expenditure of solar energy on Earth. The earth's surface, on the one hand, receives solar energy in the form of direct and diffuse radiation, and on the other hand, loses part of this energy in the form of terrestrial radiation. As a result of the arrival and consumption of solar "energy, some result is obtained. In some cases, this result can be positive, in others negative. Let's give examples of both.

January 8. The day is cloudless. For 1 cm 2 the earth's surface received per day 20 feces direct solar radiation and 12 feces scattered radiation; in total, thus received 32 cal. During the same time, due to radiation 1 cm? earth surface lost 202 cal. As a result, in the language of accounting, there is a loss of 170 feces(negative balance).

July 6th The sky is almost cloudless. 630 received from direct solar radiation cal, from scattered radiation 46 cal. In total, therefore, the earth's surface received 1 cm 2 676 cal. 173 lost by terrestrial radiation cal. In the balance sheet profit on 503 feces(balance positive).

From the above examples, among other things, it is quite clear why in temperate latitudes it is cold in winter and warm in summer.

The use of solar radiation for technical and domestic purposes. Solar radiation is an inexhaustible natural source of energy. The magnitude of solar energy on Earth can be judged by the following example: if, for example, we use the heat of solar radiation, which falls on only 1/10 of the area of ​​the USSR, then we can get energy equal to the work of 30 thousand Dneproges.

People have long sought to use the free energy of solar radiation for their needs. To date, many different solar installations have been created that operate on the use of solar radiation and are widely used in industry and to meet the household needs of the population. In the southern regions of the USSR, solar water heaters, boilers, salt water desalination plants, solar dryers (for drying fruits), kitchens, bathhouses, greenhouses, and apparatus for medical purposes operate on the basis of the widespread use of solar radiation in industry and public utilities. Solar radiation is widely used in resorts for the treatment and promotion of people's health.

Add your price to the database

Comment

The sun (astro. ☉) is the only star in the solar system. Other objects of this system revolve around the Sun: planets and their satellites, dwarf planets and their satellites, asteroids, meteoroids, comets and cosmic dust.

The internal structure of the Sun

Our Sun is a huge luminous ball of gas, within which complex processes take place and as a result, energy is continuously released. The internal volume of the Sun can be divided into several regions; the matter in them differs in its properties, and the energy is distributed through different physical mechanisms. Let's get to know them, starting from the very center.

In the central part of the Sun is the source of its energy, or, figuratively speaking, that "stove" that heats it and does not allow it to cool. This area is called the core. Under the weight of the outer layers, the matter inside the Sun is compressed, and the deeper, the stronger. Its density increases towards the center along with an increase in pressure and temperature. In the core, where the temperature reaches 15 million kelvins, energy is released.

This energy is released as a result of the fusion of atoms of light chemical elements into atoms of heavier ones. In the interior of the Sun, four hydrogen atoms form one helium atom. It was this terrible energy that people learned to release during the explosion of a hydrogen bomb. There is hope that in the near future a person will be able to learn how to use it for peaceful purposes (in 2005, news feeds were broadcast about the start of construction of the first international thermonuclear reactor in France).

The core has a radius of no more than a quarter of the total radius of the Sun. However, half of the solar mass is concentrated in its volume and almost all the energy that supports the glow of the Sun is released. But the energy of the hot core must somehow go outside, to the surface of the Sun. There are various ways of energy transfer depending on the physical conditions of the environment, namely: radiative transfer, convection and heat conduction. Thermal conductivity does not play a big role in the energy processes in the Sun and stars, while radiative and convective transport is very important.

Immediately around the nucleus, a zone of radiant energy transfer begins, where it propagates through the absorption and emission of a portion of light by the substance - quanta. Density, temperature and pressure decrease as you move away from the core, and energy flows in the same direction. In general, this process is extremely slow. For quanta to get from the center of the Sun to the photosphere, many thousands of years are needed: after all, being re-emitted, quanta change direction all the time, moving back almost as often as forward.

Gamma quanta are born in the center of the Sun. Their energy is millions of times greater than the energy of visible light quanta, and the wavelength is very small. Along the way, the quanta undergo amazing transformations. A separate quantum is first absorbed by some atom, but is immediately re-emitted; most often in this case, not one previous quantum appears, but two or more. According to the law of conservation of energy, their total energy is conserved, and therefore the energy of each of them decreases. This is how quanta of lower and lower energies arise. Powerful gamma quanta seem to be split into less energetic quanta - first x-ray, then ultraviolet and

finally visible and infrared rays. As a result, the sun emits the most energy in visible light, and it is no coincidence that our eyes are sensitive to it.

As we have already said, a quantum takes a very long time to seep through the dense solar matter to the outside. So if the “stove” inside the Sun suddenly went out, then we would know about it only millions of years later. On its way through the inner solar layers, the energy flow encounters a region where the opacity of the gas increases greatly. This is the convective zone of the Sun. Here, energy is no longer transferred by radiation, but by convection.

What is convection?

When a liquid boils, it is stirred. Gas can behave in the same way. Huge streams of hot gas rise up, where they give off their heat to the environment, and cooled solar gas descends. It looks like the solar matter is boiling and stirring. The convective zone begins approximately at a distance of 0.7 radius from the center and extends almost to the most visible surface of the Sun (photosphere), where the transfer of the main energy flux again becomes radiant. However, due to inertia, hot streams from deeper, convective layers still penetrate here. The pattern of granulation on the surface of the Sun, well known to observers, is a visible manifestation of convection.

convective zone of the sun

The radioactive zone is about 2/3 of the inner diameter of the Sun, and the radius is about 140 thousand km. Moving away from the center, photons lose their energy under the influence of the collision. This phenomenon is called the convection phenomenon. This is similar to the process that takes place in a boiling kettle: the energy coming from the heating element is much greater than the amount that heat is removed by conduction. Hot water that is near the fire rises, while colder water sinks. This process is called convention. The meaning of convection is that a denser gas is distributed over the surface, cools and again goes to the center. The mixing process in the convective zone of the Sun is continuous. Looking through a telescope at the surface of the Sun, you can see its granular structure - granulation. The feeling is that it consists of granules! This is due to convection occurring under the photosphere.

photosphere of the sun

A thin layer (400 km) - the photosphere of the Sun, is located directly behind the convective zone and represents the "real solar surface" visible from the Earth. For the first time, the granules on the photosphere were photographed by the Frenchman Janssen in 1885. An average granule has a size of 1000 km, moves at a speed of 1 km/sec, and exists for about 15 minutes. Dark formations on the photosphere can be observed in the equatorial part, and then they shift. The strongest magnetic fields are a hallmark of such spots. And the dark color is obtained due to the lower temperature relative to the surrounding photosphere.

Chromosphere of the Sun

The solar chromosphere (colored sphere) is a dense layer (10,000 km) of the solar atmosphere, which is located directly behind the photosphere. It is rather problematic to observe the chromosphere, due to its close location to the photosphere. It is best seen when the Moon closes the photosphere, i.e. during solar eclipses.

Solar prominences are huge emissions of hydrogen resembling glowing long filaments. Prominences rise to great distances, reaching the diameter of the Sun (1.4 mln km), move at a speed of about 300 km/sec, and the temperature at the same time reaches 10,000 degrees.

solar corona

The solar corona is the outer and extended layers of the Sun's atmosphere, originating above the chromosphere. The length of the solar corona is very long and reaches several solar diameters. To the question of where exactly it ends, scientists have not yet received a definite answer.

The composition of the solar corona is a rarefied, highly ionized plasma. It contains heavy ions, electrons with a nucleus of helium and protons. The temperature of the corona reaches from 1 to 2 million degrees K, relative to the surface of the Sun.

The solar wind is a continuous outflow of matter (plasma) from the outer shell of the solar atmosphere. It consists of protons, atomic nuclei and electrons. The speed of the solar wind can vary from 300 km/sec to 1500 km/sec, in accordance with the processes taking place on the Sun. The solar wind spreads throughout the solar system and, interacting with the Earth's magnetic field, causes various phenomena, one of which is the northern lights.

Sun radiation

The sun radiates its energy in all wavelengths, but in different ways. Approximately 44% of the radiation energy is in the visible part of the spectrum, and the maximum corresponds to the yellow-green color. About 48% of the energy lost by the Sun is carried away by infrared rays of the near and far range. Gamma rays, X-rays, ultraviolet and radio radiation account for only about 8%.

The visible part of solar radiation, when studied with the help of spectrum-analyzing instruments, turns out to be inhomogeneous - absorption lines are observed in the spectrum, first described by J. Fraunhofer in 1814. These lines arise when photons of certain wavelengths are absorbed by atoms of various chemical elements in the upper, relatively cold, layers of the Sun's atmosphere. Spectral analysis makes it possible to obtain information about the composition of the Sun, since a certain set of spectral lines characterizes a chemical element extremely accurately. So, for example, with the help of observations of the spectrum of the Sun, the discovery of helium was predicted, which was isolated on Earth later.

Types of radiation

In the course of observations, scientists found that the Sun is a powerful source of radio emission. Radio waves penetrate into interplanetary space, which are emitted by the chromosphere (centimeter waves) and the corona (decimeter and meter waves). The radio emission of the Sun has two components - constant and variable (bursts, "noise storms"). During strong solar flares, the radio emission from the Sun increases thousands and even millions of times compared to the radio emission from the quiet Sun. This radio emission has a non-thermal nature.

X-rays come mainly from the upper layers of the chromosphere and the corona. The radiation is especially strong during the years of maximum solar activity.

The sun emits not only light, heat and all other types of electromagnetic radiation. It is also a source of a constant flow of particles - corpuscles. Neutrinos, electrons, protons, alpha particles, and heavier atomic nuclei all together make up the corpuscular radiation of the Sun. A significant part of this radiation is a more or less continuous outflow of plasma - the solar wind, which is a continuation of the outer layers of the solar atmosphere - the solar corona. Against the background of this constantly blowing plasma wind, individual regions on the Sun are sources of more directed, enhanced, so-called corpuscular flows. Most likely, they are associated with special regions of the solar corona - coronary holes, and also, possibly, with long-lived active regions on the Sun. Finally, the most powerful short-term particle fluxes, mainly electrons and protons, are associated with solar flares. As a result of the most powerful flashes, particles can acquire velocities that make up a significant fraction of the speed of light. Particles with such high energies are called solar cosmic rays.

Solar corpuscular radiation has a strong influence on the Earth, and above all on the upper layers of its atmosphere and magnetic field, causing many geophysical phenomena. The magnetosphere and the Earth's atmosphere protect us from the harmful effects of solar radiation.

Solar radiation intensity

Having extremely high temperatures, the Sun is a very strong source of radiation. The visible range of solar radiation has the highest radiation intensity. At the same time, a large amount of the invisible spectrum also reaches the Earth. Processes take place inside the Sun, in which helium atoms are synthesized from hydrogen atoms. These processes are called nuclear fusion processes, they are accompanied by the release of a huge amount of energy. This energy leads to the fact that the Sun is heated to a temperature of 15 million degrees Celsius (in its inner part).

On the surface of the Sun (photosphere), the temperature reaches 5500 °C. On this surface, the Sun radiates energy with a value of 63 MW / m². Only a small part of this radiation reaches the surface of the Earth, which allows humanity to comfortably exist on our planet. The average intensity of radiation to the Earth's atmosphere is approximately equal to 1367 W/m². This value can fluctuate in the range of 5% due to the fact that, moving in an elliptical orbit, the Earth moves away from the Sun at different distances during the year. The value of 1367 W/m² is called the solar constant.

Solar energy on the Earth's surface

The Earth's atmosphere does not allow all solar energy to pass through. The Earth's surface reaches no more than 1000 W/m2. Part of the energy is absorbed, part is reflected in the layers of the atmosphere and in the clouds. A large amount of radiation is scattered in the layers of the atmosphere, resulting in the formation of scattered radiation (diffuse). On the Earth's surface, too, part of the radiation is reflected and becomes scattered. The sum of scattered and direct radiation is called total solar radiation. Scattered radiation can be from 20 to 60%.

The amount of energy reaching the Earth's surface is also affected by latitude and time of year. The axis of our planet, passing through the poles, is inclined by 23.5 ° relative to the orbit of rotation around the Sun. Between March

Until September, sunlight hits the Northern Hemisphere more, the rest of the time - the Southern. Therefore, the length of the day in summer and winter is different. The latitude of the area affects the length of daylight hours. The further north, the longer in the summer and vice versa.

Sun evolution

It is assumed that the Sun was born in a compressed gas and dust nebula. There are at least two theories as to what gave rise to the initial contraction of the nebula. According to one of them, it is assumed that one of the spiral arms of our galaxy passed through our region of space about 5 billion years ago. This could cause slight compression and lead to the formation of gravity centers in the gas-dust cloud. Indeed, now along the spiral arms we see a fairly large number of young stars and luminous gas clouds. Another theory suggests that somewhere nearby (on the scale of the universe, of course) an ancient massive supernova exploded. The resulting shock wave could be strong enough to initiate star formation in "our" gas-dust nebula. This theory is supported by the fact that scientists, studying meteorites, discovered quite a lot of elements that could be formed during a supernova explosion.

Further, when such a grandiose mass (2 * 1030 kg) was compressed under the influence of gravitational forces, it itself was strongly heated by internal pressure to temperatures at which thermonuclear reactions could begin in its center. In the central part, the temperature on the Sun is 15,000,000K, and the pressure reaches hundreds of billions of atmospheres. So a newborn star was lit (do not confuse with new stars).

Basically, the Sun at the beginning of its life consisted of hydrogen. It is hydrogen that in the course of thermonuclear reactions turns into helium, while the energy emitted by the Sun is released. The sun belongs to a type of star called a yellow dwarf. It is a main sequence star and belongs to the spectral type G2. The mass of a lone star quite unambiguously determines its fate. During its lifetime (~5 billion years), in the center of our star, where the temperature is quite high, about half of all the hydrogen available there burned out. Approximately the same, 5 billion years, the Sun has left to live in the form to which we are accustomed.

After hydrogen is running out in the center of the star, the Sun will increase in size and become a red giant. This will have a profound effect on the Earth: the temperature will rise, the oceans will boil away, life will become impossible. Then, having exhausted the "fuel" completely and no longer having the strength to hold the outer layers of the red giant, our star will end its life as a white dwarf, delighting extraterrestrial astronomers of the future unknown to us with a new planetary nebula, the shape of which may turn out to be very bizarre due to the influence of the planets.

Death of the Sun by Time

• Already in 1.1 billion years, the star will increase its brightness by 10%, which will lead to a strong heating of the Earth.
• After 3.5 billion years, the brightness will increase by 40%. The oceans will begin to evaporate and all life on Earth will end.
• After 5.4 billion years, the core of the star will run out of fuel - hydrogen. The sun will begin to increase in size, due to the rarefaction of the outer shell and heating of the core.
• After 7.7 billion years, our star will turn into a red giant, because. increase 200 times because of this, the planet Mercury will be absorbed.
• At the end, after 7.9 billion years, the outer layers of the star will be so rarefied that they will disintegrate into a nebula, and in the center of the former Sun there will be a small object - a white dwarf. This is how our solar system will end. All building elements left after the collapse will not be lost, they will become the basis for the birth of new stars and planets.

1. The most common stars in the universe are red dwarfs. Much of this is due to their low mass, which allows them to live for a very long time before becoming white dwarfs.
2. Almost all stars in the universe have the same chemical composition and the fusion reaction takes place in every star and is almost identical, determined only by the supply of fuel.
3. As we know, like a white dwarf, neutron stars are one of the final processes in the evolution of stars, largely arising after a supernova explosion. Previously, it was often difficult to distinguish a white dwarf from a neutron star, but now scientists using telescopes have found differences in them. A neutron star collects more light around it and this is easy to see with infrared telescopes. Eighth place among interesting facts about the stars.
4. Due to its incredible mass, according to Einstein's general theory of relativity, a black hole is actually a bend in space such that everything within their gravitational field is pushed towards it. The gravitational field of a black hole is so strong that even light cannot escape it.
5. As far as we know, when a star runs out of fuel, the star can grow in size by more than 1000 times, then it turns into a white dwarf, and because of the speed of the reaction, it explodes. This reaction is more commonly known as a supernova. Scientists suggest that in connection with this long process, such mysterious black holes are formed.
6. Many of the stars we see in the night sky can seem like a single glimmer of light. However, this is not always the case. Most of the stars we see in the sky are actually two star systems, or binary star systems. They are simply unimaginably far away and it seems to us that we see only one speck of light.
7. The stars that have the shortest lifespan are the most massive. They are a high mass of chemicals and tend to burn their fuel much faster.
8. Despite the fact that sometimes it seems to us that the Sun and stars twinkle, in fact it is not. The twinkling effect is just light from the star that is currently passing through the Earth's atmosphere but has not yet reached our eyes. Third place among the most interesting facts about the stars.
9. The distances involved in estimating how far to a star are unimaginably huge. Consider an example: The nearest star to the earth is at a distance of about 4.2 light years, and to get to it, even on our fastest ship, it will take about 70,000 years.
10. The coldest known star is the brown dwarf CFBDSIR 1458+10B, which has a temperature of only around 100°C. The hottest known star is a blue supergiant located in the Milky Way called "Zeta Purus" with a temperature of over 42,000 °C.

Solar radiation is the radiation inherent in the luminary of our planetary system. The Sun is the main star around which the Earth revolves, as well as neighboring planets. In fact, this is a huge hot gas ball, constantly emitting energy flows into the space around it. This is what they call radiation. Deadly, at the same time it is this energy - one of the main factors that make life possible on our planet. Like everything in this world, the benefits and harms of solar radiation for organic life are closely interrelated.

General view

To understand what solar radiation is, you must first understand what the Sun is. The main source of heat, which provides the conditions for organic existence on our planet, in the universal spaces is only a small star on the galactic outskirts of the Milky Way. But for earthlings, the Sun is the center of a mini-universe. After all, it is around this gas clot that our planet revolves. The sun gives us heat and light, that is, it supplies forms of energy without which our existence would be impossible.

In ancient times, the source of solar radiation - the Sun - was a deity, an object worthy of worship. The solar trajectory across the sky seemed to people an obvious proof of God's will. Attempts to delve into the essence of the phenomenon, to explain what this luminary is, have been made for a long time, and Copernicus made a particularly significant contribution to them, having formed the idea of ​​heliocentrism, which was strikingly different from the geocentrism generally accepted in that era. However, it is known for certain that even in ancient times, scientists thought more than once about what the Sun is, why it is so important for all forms of life on our planet, why the movement of this luminary is exactly the way we see it.

The progress of technology has made it possible to better understand what the Sun is, what processes take place inside the star, on its surface. Scientists have learned what solar radiation is, how a gas object affects the planets in its zone of influence, in particular, the earth's climate. Now humanity has a sufficiently large knowledge base to say with confidence: it was possible to find out what the radiation emitted by the Sun is, how to measure this energy flow and how to formulate the features of its impact on various forms of organic life on Earth.

About terms

The most important step in mastering the essence of the concept was made in the last century. It was then that the eminent astronomer A. Eddington formulated an assumption: thermonuclear fusion occurs in the solar depths, which allows a huge amount of energy to be released into the space around the star. Trying to estimate the amount of solar radiation, efforts were made to determine the actual parameters of the environment on the star. Thus, the core temperature, according to scientists, reaches 15 million degrees. This is sufficient to cope with the mutual repulsive influence of protons. The collision of units leads to the formation of helium nuclei.

New information attracted the attention of many prominent scientists, including A. Einstein. In an attempt to estimate the amount of solar radiation, scientists found that helium nuclei are inferior in mass to the total value of 4 protons required to form a new structure. Thus, a feature of the reactions, called the "mass defect", was revealed. But in nature, nothing can disappear without a trace! In an attempt to find "escaped" quantities, scientists compared the energy recovery and the specifics of the change in mass. It was then that it was possible to reveal that the difference is emitted by gamma quanta.

The radiated objects make their way from the core of our star to its surface through numerous gaseous atmospheric layers, which leads to the fragmentation of elements and the formation of electromagnetic radiation on their basis. Among other types of solar radiation is the light perceived by the human eye. Approximate estimates suggested that the process of passage of gamma rays takes about 10 million years. Another eight minutes - and the radiated energy reaches the surface of our planet.

How and what?

Solar radiation is called the total complex of electromagnetic radiation, which is characterized by a fairly wide range. This includes the so-called solar wind, that is, the energy flow formed by electrons, light particles. At the boundary layer of the atmosphere of our planet, the same intensity of solar radiation is constantly observed. The energy of a star is discrete, its transfer is carried out through quanta, while the corpuscular nuance is so insignificant that one can consider the rays as electromagnetic waves. And their distribution, as physicists have found out, occurs evenly and in a straight line. Thus, in order to describe solar radiation, it is necessary to determine its characteristic wavelength. Based on this parameter, it is customary to distinguish several types of radiation:

• warm;
• radio wave;
• White light;
• ultraviolet;
• gamma;
• x-ray.

The ratio of infrared, visible, ultraviolet best is estimated as follows: 52%, 43%, 5%.

For a quantitative radiation assessment, it is necessary to calculate the energy flux density, that is, the amount of energy that reaches a limited area of ​​the surface in a given time period.

Studies have shown that solar radiation is mainly absorbed by the planetary atmosphere. Due to this, heating occurs to a temperature comfortable for organic life, characteristic of the Earth. The existing ozone shell allows only one hundredth of the ultraviolet radiation to pass through. At the same time, short wavelengths that are dangerous to living beings are completely blocked. Atmospheric layers are able to scatter almost a third of the sun's rays, another 20% are absorbed. Consequently, no more than half of all energy reaches the surface of the planet. It is this "residue" in science that is called direct solar radiation.

How about in more detail?

Several aspects are known that determine how intense direct radiation will be. The most significant are the angle of incidence, which depends on latitude (geographical characteristics of the terrain on the globe), the time of year, which determines how far the distance to a particular point from the radiation source is. Much depends on the characteristics of the atmosphere - how polluted it is, how many clouds there are at a given moment. Finally, the nature of the surface on which the beam falls, namely, its ability to reflect the incoming waves, plays a role.

Total solar radiation is a value that combines scattered volumes and direct radiation. The parameter used to estimate the intensity is estimated in calories per unit area. At the same time, it is remembered that at different times of the day the values ​​inherent in radiation differ. In addition, energy cannot be distributed evenly over the surface of the planet. The closer to the pole, the higher the intensity, while the snow covers are highly reflective, which means that the air does not get the opportunity to warm up. Therefore, the farther from the equator, the lower the total indicators of solar wave radiation will be.

As scientists managed to reveal, the energy of solar radiation has a serious impact on the planetary climate, subjugates the vital activity of various organisms that exist on Earth. In our country, as well as in the territory of its nearest neighbors, as in other countries located in the northern hemisphere, in winter the predominant share belongs to scattered radiation, but in summer direct radiation dominates.

infrared waves

Of the total amount of total solar radiation, an impressive percentage belongs to the infrared spectrum, which is not perceived by the human eye. Due to such waves, the surface of the planet is heated, gradually transferring thermal energy to air masses. This helps to maintain a comfortable climate, maintain conditions for the existence of organic life. If there are no serious failures, the climate remains conditionally unchanged, which means that all creatures can live in their usual conditions.

Our luminary is not the only source of infrared spectrum waves. Similar radiation is characteristic of any heated object, including an ordinary battery in a human house. It is on the principle of infrared radiation perception that numerous devices work, making it possible to see heated bodies in the dark, otherwise uncomfortable conditions for the eyes. By the way, compact devices that have become so popular recently work on a similar principle to assess through which parts of the building the greatest heat losses occur. These mechanisms are especially widespread among builders, as well as owners of private houses, as they help to identify through which areas heat is lost, organize their protection and prevent unnecessary energy consumption.

Do not underestimate the impact of infrared solar radiation on the human body just because our eyes cannot perceive such waves. In particular, radiation is actively used in medicine, since it allows to increase the concentration of leukocytes in the circulatory system, as well as to normalize blood flow by increasing the lumen of blood vessels. Devices based on the IR spectrum are used as prophylactic against skin pathologies, therapeutic in inflammatory processes in acute and chronic form. The most modern drugs help to cope with colloidal scars and trophic wounds.

It's curious

Based on the study of solar radiation factors, it was possible to create truly unique devices called thermographs. They make it possible to timely detect various diseases that are not available for detection in other ways. This is how you can find cancer or a blood clot. IR to some extent protects against ultraviolet radiation, which is dangerous for organic life, which made it possible to use waves of this spectrum to restore the health of astronauts who were in space for a long time.

The nature around us is still mysterious to this day, this also applies to radiation of various wavelengths. In particular, infrared light is still not fully explored. Scientists know that its improper use can cause harm to health. Thus, it is unacceptable to use equipment that generates such light for the treatment of purulent inflamed areas, bleeding and malignant neoplasms. The infrared spectrum is contraindicated for people suffering from impaired functioning of the heart, blood vessels, including those located in the brain.

visible light

One of the elements of total solar radiation is the light visible to the human eye. Wave beams propagate in straight lines, so there is no superposition on each other. At one time, this became the topic of a considerable number of scientific works: scientists set out to understand why there are so many shades around us. It turned out that the key parameters of light play a role:

• refraction;
• reflection;
• absorption.

As the scientists found out, objects are not capable of being sources of visible light on their own, but they can absorb radiation and reflect it. Reflection angles, wave frequency vary. Over the centuries, the human ability to see has been gradually improved, but certain limitations are due to the biological structure of the eye: the retina is such that it can perceive only certain rays of reflected light waves. This radiation is a small gap between ultraviolet and infrared waves.

Numerous curious and mysterious light features not only became the subject of many works, but also were the basis for the birth of a new physical discipline. At the same time, non-scientific practices, theories appeared, the adherents of which believe that color can affect the physical state of a person, the psyche. Based on such assumptions, people surround themselves with objects that are most pleasing to their eyes, making everyday life more comfortable.

Ultraviolet

An equally important aspect of the total solar radiation is the ultraviolet study, formed by waves of large, medium and small lengths. They differ from each other both in physical parameters and in the peculiarities of their influence on the forms of organic life. Long ultraviolet waves, for example, are mainly scattered in the atmospheric layers, and only a small percentage reaches the earth's surface. The shorter the wavelength, the deeper such radiation can penetrate human (and not only) skin.

On the one hand, ultraviolet radiation is dangerous, but without it, the existence of diverse organic life is impossible. Such radiation is responsible for the formation of calciferol in the body, and this element is necessary for the construction of bone tissue. The UV spectrum is a powerful prevention of rickets, osteochondrosis, which is especially important in childhood. In addition, such radiation:

• normalizes metabolism;
• activates the production of essential enzymes;
• enhances regenerative processes;
• stimulates blood flow;
• dilates blood vessels;
• stimulates the immune system;
• leads to the formation of endorphins, which means that nervous overexcitation decreases.

but on the other hand

It was stated above that the total solar radiation is the amount of radiation that has reached the surface of the planet and is scattered in the atmosphere. Accordingly, the element of this volume is the ultraviolet of all lengths. It must be remembered that this factor has both positive and negative aspects of influence on organic life. Sunbathing, while often beneficial, can be a health hazard. Too long exposure to direct sunlight, especially in conditions of increased activity of the luminary, is harmful and dangerous. Long-term effects on the body, as well as too high radiation activity, cause:

• burns, redness;
• edema;
• hyperemia;
• heat;
• nausea;
• vomiting.

Prolonged ultraviolet irradiation provokes a violation of appetite, the functioning of the central nervous system, and the immune system. Also, my head starts to hurt. The symptoms described are classic manifestations of sunstroke. The person himself cannot always realize what is happening - the condition worsens gradually. If it is noticeable that someone nearby has become ill, first aid should be provided. The scheme is as follows:

• help to move from under direct light to a cool shaded place;
• put the patient on his back so that the legs are higher than the head (this will help normalize blood flow);
• cool the neck and face with water, and put a cold compress on the forehead;
• unbutton a tie, belt, take off tight clothes;
• half an hour after the attack, give a drink of cool water (a small amount).

If the victim has lost consciousness, it is important to immediately seek help from a doctor. The ambulance team will move the person to a safe place and give an injection of glucose or vitamin C. The medicine is injected into a vein.

How to sunbathe properly?

In order not to learn from experience how unpleasant the excessive amount of solar radiation received during tanning can be, it is important to follow the rules of safe spending time in the sun. Ultraviolet initiates the production of melanin, a hormone that helps the skin protect itself from the negative effects of waves. Under the influence of this substance, the skin becomes darker, and the shade turns into bronze. To this day, disputes about how useful and harmful it is for a person do not subside.

On the one hand, sunburn is an attempt by the body to protect itself from excessive exposure to radiation. This increases the likelihood of the formation of malignant neoplasms. On the other hand, tan is considered fashionable and beautiful. In order to minimize risks for yourself, it is reasonable to analyze before starting beach procedures how dangerous the amount of solar radiation received during sunbathing is, how to minimize risks for yourself. To make the experience as pleasant as possible, sunbathers should:

• to drink a lot of water;
• use skin protection products;
• sunbathe in the evening or in the morning;
• spend no more than an hour under the direct rays of the sun;
• do not drink alcohol;
• include foods rich in selenium, tocopherol, tyrosine in the menu. Don't forget about beta-carotene.

The value of solar radiation for the human body is exceptionally high, both positive and negative aspects should not be overlooked. You should be aware that in different people biochemical reactions occur with individual characteristics, so for someone even half an hour sunbathing can be dangerous. It is reasonable to consult a doctor before the beach season, assess the type and condition of the skin. This will help prevent harm to health.

If possible, sunburn should be avoided in old age, during the period of bearing a baby. Cancer diseases, mental disorders, skin pathologies and heart failure are not combined with sunbathing.

Total radiation: where is the shortage?

Quite interesting to consider is the process of distribution of solar radiation. As mentioned above, only about half of all waves can reach the surface of the planet. Where do the rest disappear to? The different layers of the atmosphere and the microscopic particles from which they are formed play their role. An impressive part, as was indicated, is absorbed by the ozone layer - these are all waves whose length is less than 0.36 microns. Additionally, ozone is able to absorb some types of waves from the spectrum visible to the human eye, that is, the interval of 0.44-1.18 microns.

The ultraviolet is absorbed to some extent by the oxygen layer. This is characteristic of radiation with a wavelength of 0.13-0.24 microns. Carbon dioxide, water vapor can absorb a small percentage of the infrared spectrum. Atmospheric aerosol absorbs some part (IR spectrum) of the total amount of solar radiation.

Waves from the short category are scattered in the atmosphere due to the presence of microscopic inhomogeneous particles, aerosol, and clouds here. Inhomogeneous elements, particles whose dimensions are inferior to the wavelength, provoke molecular scattering, and for larger ones, the phenomenon described by the indicatrix, that is, aerosol, is characteristic.

The rest of the solar radiation reaches the earth's surface. It combines direct radiation, diffused.

Total radiation: important aspects

The total value is the amount of solar radiation received by the territory, as well as absorbed in the atmosphere. If there are no clouds in the sky, the total amount of radiation depends on the latitude of the area, the altitude of the celestial body, the type of earth's surface in this area, and the level of air transparency. The more aerosol particles scattered in the atmosphere, the lower the direct radiation, but the proportion of scattered radiation increases. Normally, in the absence of cloudiness in the total radiation, diffuse is one fourth.

Our country belongs to the northern ones, so for most of the year in the southern regions the radiation is significantly higher than in the northern ones. This is due to the position of the star in the sky. But the short time period May-July is a unique period, when even in the north the total radiation is quite impressive, since the sun is high in the sky, and the daylight hours are longer than in other months of the year. At the same time, on average, in the Asian half of the country, in the absence of clouds, the total radiation is more significant than in the west. The maximum strength of wave radiation is observed at noon, and the annual maximum occurs in June, when the sun is highest in the sky.

Total solar radiation is the amount of solar energy reaching our planet. At the same time, it must be remembered that various atmospheric factors lead to the fact that the annual arrival of total radiation is less than it could be. The biggest difference between the actually observed and the maximum possible is typical for the Far Eastern regions in the summer. Monsoons provoke exceptionally dense clouds, so the total radiation is reduced by about half.

curious to know

The largest percentage of the maximum possible exposure to solar energy is actually observed (calculated for 12 months) in the south of the country. The indicator reaches 80%.

Cloudiness does not always result in the same amount of solar scatter. The shape of the clouds plays a role, the features of the solar disk at a particular point in time. If it is open, then the cloudiness causes a decrease in direct radiation, while the scattered radiation increases sharply.

There are also days when direct radiation is approximately the same in strength as scattered radiation. The daily total value can be even greater than the radiation characteristic of a completely cloudless day.

Based on 12 months, special attention should be paid to astronomical phenomena as determining the overall numerical indicators. At the same time, cloudiness leads to the fact that the real radiation maximum can be observed not in June, but a month earlier or later.

Radiation in space

From the boundary of the magnetosphere of our planet and further into outer space, solar radiation becomes a factor associated with a mortal danger to humans. As early as 1964, an important popular science work on defense methods was published. Its authors were Soviet scientists Kamanin, Bubnov. It is known that for a person, the radiation dose per week should be no more than 0.3 roentgens, while for a year it should be within 15 R. For short-term exposure, the limit for a person is 600 R. Flights into space, especially in conditions of unpredictable solar activity , may be accompanied by significant exposure of astronauts, which obliges to take additional measures to protect against waves of different lengths.

After the Apollo missions, during which methods of protection were tested, factors affecting human health were studied, more than one decade passed, but to this day scientists cannot find effective, reliable methods for predicting geomagnetic storms. You can make a forecast for hours, sometimes for several days, but even for a weekly forecast, the chances of realization are no more than 5%. The solar wind is an even more unpredictable phenomenon. With a probability of one in three, astronauts, setting off on a new mission, can fall into powerful radiation fluxes. This makes even more important the issue of both research and prediction of radiation features, and the development of methods of protection against it.

shortwave radiation from the sun

Ultraviolet and X-rays come mainly from the upper layers of the chromosphere and the corona. This was established by launching rockets with instruments during solar eclipses. The very hot solar atmosphere always emits invisible short-wave radiation, but it is especially powerful during the years of maximum solar activity. At this time, ultraviolet radiation increases by about a factor of two, and X-ray radiation by tens and hundreds of times compared to the radiation in years of minimum. The intensity of shortwave radiation varies from day to day, increasing sharply when flares occur.

Ultraviolet and X-ray radiation partially ionize the layers of the earth's atmosphere, forming the ionosphere at altitudes of 200-500 km from the Earth's surface. The ionosphere plays an important role in the implementation of long-range radio communications: radio waves coming from a radio transmitter, before reaching the receiver antenna, are repeatedly reflected from the ionosphere and the Earth's surface. The state of the ionosphere varies depending on the conditions of its illumination by the Sun and on the phenomena occurring on it. Therefore, to ensure stable radio communication, it is necessary to take into account the time of day, season and the state of solar activity. After the most powerful solar flares, the number of ionized atoms in the ionosphere increases and radio waves are partially or completely absorbed by it. This leads to deterioration and even to a temporary cessation of radio communications.

Scientists pay special attention to the study of the ozone layer in the earth's atmosphere. Ozone is formed as a result of photochemical reactions (absorption of light by oxygen molecules) in the stratosphere, and its bulk is concentrated there. In total, there are approximately 3 10 9 tons of ozone in the earth's atmosphere. This is very small: the thickness of the pure ozone layer near the Earth's surface would not exceed 3 mm! But the role of the ozone layer, which extends at a height of several tens of kilometers above the Earth's surface, is exceptionally great, because it protects all living things from the effects of dangerous short-wave (and, above all, ultraviolet) radiation from the Sun. The ozone content is not constant at different latitudes and at different times of the year. It can decrease (sometimes very significantly) as a result of various processes. This can be facilitated, for example, by emissions of large amounts of ozone-depleting chlorine-containing substances from industrial origin or aerosol emissions into the atmosphere, as well as emissions accompanying volcanic eruptions. Areas of a sharp decrease in the ozone level (“ozone holes”) were found over different regions of our planet, not only over Antarctica and a number of other territories of the Southern Hemisphere of the Earth, but also over the Northern Hemisphere. In 1992, alarming reports began to appear of temporary depletion of the ozone layer over northern European Russia and a decrease in ozone over Moscow and St. Petersburg. Scientists, realizing the global nature of the problem, organize environmental research on a global scale, including primarily a global system of continuous monitoring of the state of the ozone layer. International agreements have been developed and signed to protect the ozone layer and limit the production of ozone-depleting substances.

Sun radio emission

A systematic study of the radio emission of the Sun began only after the Second World War, when it was discovered that the Sun is a powerful source of radio emission. Radio waves penetrate into interplanetary space, which are emitted by the chromosphere (centimeter waves) and the corona (decimeter and meter waves). This radio emission reaches the Earth. The radio emission of the Sun has two components - a constant, almost unchanged in intensity, and a variable (bursts, "noise storms").

The radio emission of the quiet Sun is explained by the fact that hot solar plasma always emits radio waves along with electromagnetic oscillations of other wavelengths (thermal radio emission). During large flares, the radio emission from the Sun increases by thousands and even millions of times compared to the radio emission from the quiet Sun. This radio emission, generated by fast non-stationary processes, has a non-thermal nature.

Corpuscular radiation of the Sun

A number of geophysical phenomena (magnetic storms, i.e. short-term changes in the Earth's magnetic field, auroras, etc.) are also associated with solar activity. But these phenomena occur a day after solar flares. They are caused not by electromagnetic radiation reaching the Earth in 8.3 minutes, but by corpuscles (protons and electrons forming a rarefied plasma), which penetrate the near-Earth space with a delay (by 1-2 days), since they move at speeds of 400 - 1000 km /c.

Corpuscles are emitted by the Sun even when there are no flashes and spots on it. The solar corona is the source of a constant outflow of plasma (solar wind) that occurs in all directions. The solar wind, created by the continuously expanding corona, envelops the planets moving near the Sun and . Flares are accompanied by "gusts" of the solar wind. Experiments at interplanetary stations and artificial Earth satellites made it possible to directly detect the solar wind in interplanetary space. During flares and during a calm outflow of the solar wind, not only corpuscles but also the magnetic field associated with the moving plasma penetrate into interplanetary space.