Sun spots

The Sun is the only one of all the stars that we see not as a sparkling point, but as a shining disk. Thanks to this, astronomers are able to study various details on its surface.

What is it sunspots?

Sunspots are far from stable formations. They arise, develop and disappear, and new ones appear to replace those that have disappeared. Occasionally giant spots form. Thus, in April 1947, a complex spot was observed on the Sun: its area exceeded the surface area globe 350 times! It was clearly visible to the naked eye 1.

Sun spots

Such large spots on the Sun have been noticed since ancient times. In the Nikon Chronicle for 1365 one can find a mention of how our ancestors in Rus' saw “dark spots, like nails” on the Sun through the smoke of forest fires.

Appearing on the eastern (left) edge of the Sun, moving along its disk from left to right and disappearing behind the western (right) edge of the daylight, sunspots provide an excellent opportunity not only to verify the rotation of the Sun around its axis, but also to determine the period of this rotation (more precisely, it determined by the Doppler shift of spectral lines). Measurements showed: the period of rotation of the Sun at the equator is 25.38 days (relative to an observer on a moving Earth - 27.3 days), in mid-latitudes - 27 days and at the poles about 35 days. Thus, the Sun rotates faster at the equator than at the poles. Zone rotation the luminary indicates its gaseous state. The central part of the large spot looks completely black in a telescope. But the spots only appear dark because we observe them against the background of a bright photosphere. If the spot could be examined separately, we would see that it glows stronger than an electric arc, since its temperature is about 4,500 K, that is, 1,500 K less than the temperature of the photosphere. A medium-sized sunspot against the night sky would appear as bright as the Moon at full moon. Only the spots emit not yellow, but reddish light.

Typically, the dark core of a large spot is surrounded by a gray penumbra, consisting of light radial fibers located on a dark background. This entire structure is clearly visible even with a small telescope.

Sun spots

Back in 1774, Scottish astronomer Alexander Wilson (1714-1786), observing spots at the edge of the solar disk, concluded that large spots were depressions in the photosphere. Subsequent calculations showed that the “bottom” of the spot lies below the level of the photosphere by an average of 700 km. In a word, spots are giant funnels in the photosphere.

Around the spots in the hydrogen rays the vortex structure of the chromosphere is clearly visible. This vortex structure indicates the existence of violent gas movements around the spot. The same pattern is created by iron filings poured onto a sheet of cardboard if a magnet is placed under them. This similarity led the American astronomer George Hale (1868-1938) to suspect that sunspots are huge magnets.

Hale knew that spectral lines are split if the emitting gas is in a magnetic field (the so-called Zeeman splitting). And when the astronomer compared the amount of splitting observed in the spectrum of sunspots with the results of laboratory experiments With gas in a magnetic field, he discovered that the magnetic fields of the spots are thousands of times higher than the induction of the earth's magnetic field. Tension magnetic field at the Earth's surface is about 0.5 oersted. And in sunspots it is always more than 1500 oersteds - sometimes reaches 5000 oersteds!

The discovery of the magnetic nature of sunspots is one of the most important discoveries in astrophysics at the beginning of the 20th century. For the first time it was established that not only our Earth, but also other celestial bodies have magnetic properties. The sun came to the fore in this regard. Only our planet has a constant dipole magnetic field with two poles, and the magnetic field of the Sun has a complex structure, and what’s more, it “turns over”, that is, it changes its sign, or polarity. And although sunspots are very strong magnets, the total magnetic field of the Sun rarely exceeds 1 oersted, which is several times the average field of the Earth.

Strong magnetic field in a bipolar sunspot group

The strong magnetic field of the sunspots is precisely the reason for their low temperature. After all, the field creates an insulating layer under the sunspot and, thanks to this, sharply slows down the convection process - reduces the flow of energy from the depths of the star.

Large spots prefer to appear in pairs. Each such pair is located almost parallel to the solar equator. The leading, or head, spot usually moves a little faster than the trailing (tail) spot. Therefore, during the first few days the spots move away from each other. At the same time, the size of the spots increases.

Often, a “chain” of small spots appears in between the two main spots. Once this happens, the tail spot may undergo rapid disintegration and disappear. Only the leading spot remains, which decreases more slowly and lives on average 4 times longer than its companion. A similar development process is characteristic of almost every large group sunspots. Most spots last only a few days (even a few hours!), while others last for several months.

The spots, the diameter of which reaches 40-50 thousand km, can be seen through a filter (densely smoked glass) with the naked eye.

What are solar flares?

On September 1, 1859, two English astronomers - Richard Carrington and S. Hodgson, independently observing the Sun in white light, saw something like lightning flash suddenly among one group of sunspots. This was the first observation of a new, still unknown phenomenon on the Sun; it was later called a solar flare.

What is a solar flare? In short, this is a powerful explosion on the Sun, as a result of which a colossal amount of energy accumulated in a limited volume of the solar atmosphere is quickly released.

Most often, flares occur in neutral areas located between large spots of opposite polarity. Typically, the development of a flare begins with a sudden increase in the brightness of the flare area - an area of ​​\u200b\u200bbrighter, and therefore hotter, photosphere. Then a catastrophic explosion occurs, during which the solar plasma heats up to 40-100 million K. This manifests itself in a multiple increase in the short-wave radiation of the Sun (ultraviolet and x-rays), as well as in an increase in the “radio voice” of the daylight and in the emission of accelerated solar corpuscles (particles) . And some of the most powerful flares even generate solar cosmic rays, the protons of which reach a speed equal to half the speed of light. Such particles have deadly energy. They are able to penetrate almost unhindered spaceship and destroy the cells of a living organism. Therefore, solar cosmic rays can pose a serious danger to a crew caught in a sudden flash during a flight.

Thus, solar flares emit radiation in the form of electromagnetic waves and in the form of particles of matter. The amplification of electromagnetic radiation occurs in a wide range of wavelengths - from hard X-rays and gamma rays to kilometer-long radio waves. In this case, the total flux of visible radiation always remains constant to within a fraction of a percent. Weak flares on the Sun almost always occur, and large ones occur once every few months. But during the years of maximum solar activity, large solar flares occur several times a month. Typically a small flash lasts 5-10 minutes; the most powerful - several hours. During this time, a cloud of plasma weighing up to 10 billion tons is ejected into the near-solar space and energy is released equivalent to the explosion of tens or even hundreds of millions of hydrogen bombs! However, the power of even the largest flares does not exceed hundredths of a percent of the power of the total radiation of the Sun. Therefore, during a flare there is no noticeable increase in the luminosity of our daylight.

During the flight of the first crew on the American orbital station Skylab (May-June 1973), it was possible to photograph a flash in the light of iron vapor at a temperature of 17 million K, which should be hotter than in the center of the sun fusion reactor. And in last years Pulses of gamma radiation were recorded from several flares.

Such impulses probably owe their origin to annihilation electron-positron pairs. The positron, as is known, is the antiparticle of the electron. It has the same mass as an electron, but is endowed with the opposite electrical charge. When an electron and a positron collide, as can happen in solar flares, they are immediately destroyed, turning into two photons of gamma rays.

Like any heated body, the Sun continuously emits radio waves. Thermal radio emission from the quiet sun, when there are no spots or flashes on it, it constantly comes from the chromosphere at millimeter and centimeter waves, and from the corona at meter waves. But as soon as large spots appear, a flare occurs, strong radio waves arise against the background of calm radio emission. radio bursts... And then the radio emission of the Sun increases abruptly by thousands, or even millions of times!

The physical processes leading to solar flares are very complex and still poorly understood. However, the very fact that solar flares appear almost exclusively in large groups of sunspots indicates that flares are related to strong magnetic fields on the Sun. And the flare is, apparently, nothing more than a colossal explosion caused by the sudden compression of solar plasma under the pressure of a strong magnetic field. It is the energy of magnetic fields, somehow released, that gives rise to a solar flare.

Radiation from solar flares often reaches our planet, having a strong impact on the upper layers of the earth's atmosphere (ionosphere). They also lead to the emergence of magnetic storms and auroras, but more on that in the future.

Rhythms of the Sun

In 1826, a German amateur astronomer, pharmacist Heinrich Schwabe (1789-1875) from Dessau, began systematic observations and sketches of sunspots. No, he did not intend to study the Sun at all - he was interested in something completely different. At that time it was thought that an unknown planet was moving between the Sun and Mercury. And since it was impossible to see it close to the bright star, Schwabe decided to observe everything that was visible on the solar disk. After all, if such a planet really exists, then sooner or later it will certainly pass across the disk of the Sun in the form of a small black circle or dot. And then she will finally be “caught”!

However, Schwabe, in his own words, “went in search of his father’s donkeys and found the kingdom.” In 1851, in the book “Cosmos” by Alexander Humboldt (1769-1859), the results of Schwabe’s observations were published, from which it followed that the number of sunspots increases and decreases quite regularly over a 10-year period. This periodicity in the change in the number of sunspots, later called 11 year cycle solar activity, was discovered by Heinrich Schwabe in 1843. Subsequent observations confirmed this discovery, and the Swiss astronomer Rudolf Wolf (1816-1893) clarified that the maxima in the number of sunspots repeat on average every 11.1 years.

So, the number of spots varies from day to day and from year to year. To judge the degree of solar activity based on sunspot counts, in 1848 Wolf introduced the concept of the relative number of sunspots, or the so-called Wolf numbers. If we denote by g the number of groups of spots, and by f the total number of spots, then the Wolf number - W - is expressed by the formula:

This number, which determines the measure of sunspot activity of the Sun, takes into account both the number of groups of sunspots and the number of sunspots themselves observed on a particular day. Moreover, each group is equal to ten units, and each spot is taken as a unit. The total score for the day - the relative Wolf number - is the sum of these numbers. Let's say that we observe 23 spots on the Sun, which form three groups. Then the Wolf number in our example will be: W = 10 3 + 23 = 53. During periods of minimum solar activity, when there is not a single spot on the Sun, it turns to zero. If there is only one spot on the Sun, then the Wolf number will be equal to 11, and on days of maximum solar activity it is sometimes more than 200.

The curve of the average monthly number of sunspots clearly shows the nature of changes in solar activity. Such data is available from 1749 to the present. Averaging done over 200 years determined the period of change of sunspots to be 11.2 years. True, over the past 60 years, the sunspot activity of our daylight has accelerated somewhat and this period has decreased to 10.5 years. In addition, its duration varies noticeably from cycle to cycle. Therefore, we should talk not about the periodicity of solar activity, but about cyclicity. The eleven year cycle is most important feature our Sun.

With his discovery of the magnetic field of sunspots in 1908, George Hale also discovered the law of alternation of their polarity. We have already said that in the developed group there are two large spots - two large magnets. They have opposite polarity. The sequence of polarities in the northern and southern hemispheres of the Sun is also always opposite. If in the northern hemisphere the leading (head) sunspot has, for example, northern polarity, and the trailing (tail) sunspot has southern polarity, then in the southern hemisphere of the daylight the picture will be the opposite: the leading sunspot has southern polarity, and the trailing sunspot has northern polarity. But the most remarkable thing is that in the next 11-year cycle, the polarities of all spots in groups in both hemispheres of the Sun change to the opposite, and with the onset of a new cycle they return to their original state. Thus, magnetic cycle of the sun is approximately 22 years old. Therefore, many solar astronomers consider the main 22-year cycle of solar activity, associated with a change in the polarity of the magnetic field in sunspots.

It has long been established that in time with the change in the number of spots on the Sun, the areas of flare sites and the power of solar flares change. These and other phenomena that occur V atmosphere of the Sun, now commonly called solar activity. Its most accessible element for observation is large groups sunspots.

Now it’s time to answer perhaps the most intriguing question: “Where does solar activity come from and how can its features be explained?”

Since the determining factor in solar activity is the magnetic field, the emergence and development of a bipolar group of sunspots - an active region on the Sun - can be represented as the result of the gradual ascent into the solar atmosphere of a huge magnetic rope or tube, which emerges from one spot and, forming an arch, enters another spot. At the point where the tube leaves the photosphere, a spot appears with one polarity of the magnetic field, and where it reenters the photosphere - with the opposite polarity. After some time, this magnetic tube collapses, and the remnants of the magnetic rope sink back under the photosphere and the active region on the Sun disappears. In this case, part of the magnetic field lines goes into the chromosphere and the solar corona. Here the magnetic field sort of orders the moving plasma, as a result of which solar matter moves along the magnetic field lines. This gives the crown a radiant appearance. The fact that active regions on the Sun are determined by magnetic flux tubes is no longer in doubt among scientists. Magnetohydrodynamic effects also explain the change in field polarity in bipolar groups of sunspots. But these are only the first steps towards building a scientifically based theory that can explain all the observed features of the activity of the great luminary.

Average annual Wolf numbers from 1947 to 2001

Photosphere of the Sun

Explanation of the appearance of bipolar magnetic regions on the Sun. A huge magnetic tube rises from the convective zone into the solar atmosphere

So, on the Sun there is an eternal struggle between the pressure forces of hot gas and monstrous gravity. And entangled magnetic fields stand in the way of radiation. Spots appear and collapse in their networks. Along the power lines magnetic lines high-temperature plasma flies up or slides down from the corona. Where else can you find something like this?! Only on other stars, but they are terribly far from us! And only on the Sun can we observe this eternal struggle of the forces of nature, which has been going on for 5 billion years. And only gravity will win in it!

"Echo" of solar flares

On February 23, 1956, the Sun Service stations noted a powerful flare on the daylight. In an explosion of unprecedented force, giant clouds of hot plasma were thrown into the circumsolar space - each many times larger. more than Earth! And at a speed of more than 1000 km/s they rushed towards our planet. The first echoes of this catastrophe quickly reached us across the cosmic abyss. Approximately 8.5 minutes after the start of the flare, a greatly increased flow of ultraviolet and X-rays reached the upper layers of the earth's atmosphere - the ionosphere, intensifying its heating and ionization. This led to a sharp deterioration and even temporary cessation of radio communications on short waves, because instead of being reflected from the ionosphere, as from a screen, they began to be intensively absorbed by it...

Change in magnetic polarity of sunspots

Sometimes, when very strong flashes, radio interference lasts for several days in a row, until the restless star “returns to normal.” The dependence can be traced here so clearly that the level of solar activity can be judged by the frequency of such interference. But the main disturbances caused on Earth by the flare activity of the star are ahead.

Following short-wave radiation (ultraviolet and x-rays), a stream of high-energy solar cosmic rays reaches our planet. True, the magnetic shell of the Earth quite reliably protects us from these deadly rays. But for astronauts working in outer space, they pose a very serious danger: radiation exposure can easily exceed permissible dose. That is why about 40 observatories around the world constantly participate in the Sun Patrol Service - they conduct continuous observations of the flare activity of the daylight.

Further development of geophysical phenomena on Earth can be expected a day or two days after the outbreak. This is exactly the time - 30-50 hours - required for the plasma clouds to reach the earth's “neighborhoods”. After all, a solar flare is something like a cosmic gun that shoots corpuscles - particles of solar matter: electrons, protons (nuclei of hydrogen atoms), alpha particles (nuclei of helium atoms) into interplanetary space. The mass of corpuscles erupted by the flare in February 1956 amounted to billions of tons!

As soon as the clouds of solar particles collided with the Earth, compass needles began to sweep, and the night sky above the planet was decorated with multi-colored flashes of the aurora. Heart attacks have increased sharply among patients, and the number of road accidents has increased.

Types of impacts of a solar flare on Earth

What about magnetic storms, auroras... Under the pressure of gigantic corpuscular clouds, literally the entire globe shook: earthquakes occurred in many seismic zones 2 . And as if to top it all off, the length of the day abruptly changed by as much as 10... microseconds!

Space research has shown that the globe is surrounded by a magnetosphere, that is, a magnetic shell; inside the magnetosphere, the strength of the Earth's magnetic field prevails over the strength of the interplanetary field. And in order for a flare to have an impact on the Earth’s magnetosphere and the Earth itself, it must occur at a time when the active region on the Sun is located near the center of the solar disk, that is, oriented towards our planet. Otherwise, all flare radiation (electromagnetic and corpuscular) will fly by.

The plasma that rushes from the surface of the Sun into outer space has a certain density and is capable of exerting pressure on any obstacles encountered along its path. Such a significant obstacle is the Earth's magnetic field - its magnetosphere. It counteracts the flow of solar matter. There comes a moment when in this confrontation both pressures are balanced. Then the boundary of the Earth's magnetosphere, pressed by the flow of solar plasma from the day side, is established at a distance of approximately 10 Earth radii from the surface of our planet, and the plasma, unable to move straight, begins to flow around the magnetosphere. In this case, particles of solar matter stretch its magnetic field lines, and on the night side of the Earth (in the direction opposite from the Sun) a long trail (tail) is formed near the magnetosphere, which extends beyond the orbit of the Moon. The earth with its magnetic shell finds itself inside this corpuscular flow. And if the ordinary solar wind, constantly flowing around the magnetosphere, can be compared to a light breeze, then the rapid flow of corpuscles generated by a powerful solar flare is like a terrible hurricane. When such a hurricane hits the magnetic shell of the globe, it contracts even more strongly on the subsolar side and plays out on Earth magnetic storm.

Thus, solar activity affects terrestrial magnetism. As it intensifies, the frequency and intensity of magnetic storms increases. But this connection is quite complex and consists of a whole chain of physical interactions. The main link in this process is the enhanced flow of corpuscles that occurs during solar flares.

Some energetic corpuscles in polar latitudes break through from a magnetic trap into earth's atmosphere. And then, at altitudes from 100 to 1000 km, fast protons and electrons, colliding with air particles, excite them and make them glow. As a result, there is Polar Lights.

Periodic “revivals” of the great luminary are a natural phenomenon. For example, after a grandiose solar flare observed on March 6, 1989, corpuscular flows excited literally the entire magnetosphere of our planet. As a result, a strong magnetic storm broke out on Earth. It was accompanied by an aurora of astonishing scope, which reached the tropical zone in the area of ​​the California Peninsula! Three days later, a new powerful outbreak occurred, and on the night of March 13-14, residents of the southern coast of Crimea also admired the enchanting flashes spread out in the starry sky above the rocky teeth of Ai-Petri. It was a unique sight, like the glow of a fire that immediately engulfed half the sky.

All the geophysical effects mentioned here - ionospheric and magnetic storms and auroras - are an integral part of the most complex scientific problem called problem "Sun-Earth". However, the influence of solar activity on Earth is not limited to this. The “breath” of the daylight constantly manifests itself in changes in weather and climate.

Climate is nothing more than the long-term weather pattern in a given area, and it is determined by its geographical location on the globe and the nature of atmospheric processes.

Leningrad scientists from the Research Institute of the Arctic and Antarctic were able to reveal that during the years of minimum solar activity, latitudinal air circulation prevails. In this case, the weather in the Northern Hemisphere becomes relatively calm. During maximum years, on the contrary, the meridional circulation intensifies, that is, there is an intensive exchange of air masses between the tropical and polar regions. The weather is becoming unstable, and significant deviations from long-term climate norms are observed.

Western Europe: British Isles in the area of ​​a strong cyclone. Photo from space

1Everyone should remember that you should never look at the Sun without protecting your eyes with dark filters. You can instantly lose your sight

2Research fellow of the Murmansk branch of the Astronomical and Geodetic Society of Russia (its chairman) Viktor Evgenievich Troshenkov studied the impact of solar activity on the tectonics of the globe. His global reanalysis seismic activity of our planet for 230 years (1750-1980) showed the presence linear dependence between Earth seismicity (earthquakes) and solar storms.

Sergey Bogachev

How are sunspots arranged?

One of the largest active regions of this year has appeared on the solar disk, which means that there are spots on the Sun again - despite the fact that our star is entering the period. Sergei Bogachev, an employee of the Laboratory of X-ray Solar Astronomy of the Lebedev Physical Institute, Doctor of Physical and Mathematical Sciences, talks about the nature and history of the discovery of sunspots, as well as their impact on the earth’s atmosphere.

In the first decade of the 17th century, the Italian scientist Galileo Galilei and the German astronomer and mechanic Christoph Scheiner approximately simultaneously and independently of each other improved the telescope (or telescope) invented several years earlier and created on its basis a helioscope - a device that allows you to observe the Sun by projecting his image on the wall. In these images they discovered details that could be mistaken for wall defects if they did not move with the image - small spots dotting the surface of the ideal (and partly divine) central celestial body - the Sun. This is how sunspots entered the history of science, and the saying that there is nothing ideal in the world came into our lives: “And there are spots on the Sun.”

Sunspots are the main feature that can be seen on the surface of our star without the use of complex astronomical equipment. The visible sizes of the spots are on the order of one arc minute (the size of a 10-kopeck coin from a distance of 30 meters), which is at the limit of resolution of the human eye. However, a very simple optical device, magnifying only a few times, is enough for these objects to be discovered, which, in fact, happened in Europe at the beginning of the 17th century. Individual observations of spots, however, regularly occurred before this, and often they were made simply by eye, but remained unnoticed or misunderstood.

For some time they tried to explain the nature of the spots without affecting the ideality of the Sun, for example, like clouds in solar atmosphere, but it quickly became clear that they relate mediocrely to the solar surface. Their nature, however, remained a mystery until the first half of the 20th century, when magnetic fields were first discovered on the Sun and it turned out that the places where they were concentrated coincided with the places where sunspots formed.

Why do the spots look dark? First of all, it should be noted that their darkness is not absolute. It is, rather, similar to the dark silhouette of a person standing against the backdrop of a lit window, that is, it is only apparent against the backdrop of very bright ambient light. If you measure the “brightness” of a spot, you will find that it also emits light, but only at a level of 20-40 percent of the normal light Sun. This fact is enough to determine the temperature of the spot without any additional measurements, since the flux of thermal radiation from the Sun is uniquely related to its temperature through the Stefan-Boltzmann law (the flux of radiation is proportional to the temperature of the radiating body to the fourth power). If we put the brightness of the normal surface of the Sun with a temperature of about 6000 degrees Celsius as a unit, then the temperature of sunspots should be about 4000-4500 degrees. Strictly speaking, this is how it is - sunspots (and this was later confirmed by other methods, for example, spectroscopic studies of radiation) are simply areas of the solar surface of lower temperature.

The connection between spots and magnetic fields is explained by the influence of the magnetic field on the temperature of the gas. This influence is due to the presence of a convective (boiling) zone in the Sun, which extends from the surface to a depth of about a third solar radius. The boiling of solar plasma continuously raises hot plasma from its depths to the surface and thereby increases the surface temperature. In areas where the surface of the Sun is pierced by tubes of a strong magnetic field, the efficiency of convection is suppressed until it stops completely. As a result, without replenishment of hot convective plasma, the surface of the Sun cools down to temperatures of about 4000 degrees. A spot forms.

Nowadays, sunspots are studied mainly as the centers of active solar regions in which solar flares are concentrated. The fact is that the magnetic field, the “source” of which are sunspots, brings into the solar atmosphere additional reserves of energy that are “extra” for the Sun, and it, like any physical system that seeks to minimize its energy, tries to get rid of them. This additional energy is called free energy. There are two main mechanisms for releasing excess energy.

The first is when the Sun simply throws out into interplanetary space the part of the atmosphere that burdens it, along with excess magnetic fields, plasma and currents. These phenomena are called coronal mass ejections. The corresponding emissions, spreading from the Sun, sometimes reach colossal sizes of several million kilometers and are, in particular, main reason magnetic storms - the impact of such a plasma clot on the Earth's magnetic field throws it out of balance, causes it to oscillate, and also intensifies the electric currents flowing in the Earth's magnetosphere, which is the essence of a magnetic storm.

The second way is solar flares. In this case, free energy is burned directly in the solar atmosphere, but the consequences of this can also reach the Earth - in the form of streams of hard radiation and charged particles. This impact, which is radiation in nature, is one of the main reasons for the failure of spacecraft, as well as auroras.

However, having discovered a sunspot on the Sun, you should not immediately prepare for solar flares and magnetic storms. A fairly common situation is when the appearance of spots on the solar disk, even record-breaking large ones, does not lead to even a minimal increase in the level of solar activity. Why is this happening? This is due to the nature of the release of magnetic energy on the Sun. Such energy cannot be released from a single magnetic flux, just as a magnet lying on a table, no matter how much it is shaken, will not create any solar flare. There must be at least two such threads, and they must be able to interact with each other.

Since one magnetic tube piercing the surface of the Sun in two places creates two spots, then all groups of spots in which there are only two or one spots are not capable of creating flares. These groups are formed by one thread, which has nothing to interact with. Such a pair of spots can be gigantic and exist on the solar disk for months, frightening the Earth with their size, but will not create a single, even minimal, flare. Such groups have a classification and are called type Alpha, if there is one spot, or Beta, if there are two.

Complex sunspot of the Beta-Gamma-Delta type. Top - visible spot, bottom - magnetic fields shown using the HMI instrument on board the SDO space observatory

If you find a message about the appearance of a new sunspot on the Sun, take the time and look at the type of group. If it is Alpha or Beta, then you don’t have to worry - the Sun will not produce any flares or magnetic storms in the coming days. More difficult class is Gamma. These are groups of sunspots in which there are several spots of northern and southern polarity. In such an area there are at least two interacting magnetic flux. Accordingly, such an area will lose magnetic energy and fuel solar activity. And finally last class- Beta Gamma. These are the most complex areas, with an extremely entangled magnetic field. If such a group appears in the catalog, there is no doubt that the Sun will unravel this system for at least several days, burning energy in the form of flares, including large ones, and ejecting plasma until it simplifies this system to a simple Alpha or Beta configuration.

However, despite the “terrifying” connection of sunspots with flares and magnetic storms, we should not forget that this is one of the most remarkable astronomical phenomena, which can be observed from the surface of the Earth with amateur instruments. Finally, sunspots are a very beautiful object - just look at their images taken from high resolution. Those who, even after this, are not able to forget about the negative aspects of this phenomenon, can be consoled by the fact that the number of spots on the Sun is still relatively small (no more than 1 percent of the disk surface, and often much less).

A number of types of stars, at least red dwarfs, “suffer” in to a greater extent- up to tens of percent of the area can be covered with spots. You can imagine what the hypothetical inhabitants of the corresponding planetary systems are like, and once again rejoice at what relatively calm star we are lucky enough to live next to.

Black spots on the surface of the Sun were noticed by our ancestors thousands of years ago, but without instruments, for a long time They couldn’t figure out what they referred to, either the Sun or the shadows of passing celestial bodies. It was only in the 17th century, using a homemade telescope, that Galileo Galilei discovered that the sunspots belonged to the Sun and rotated with it. After this discovery, the nature of the mysterious spots remained unknown for a long time. In fact, even today we cannot get close to our star in order to examine the physics of the processes in detail, despite the fact that hundreds of telescopes carefully monitor it constantly. Theorists also wander in the darkness of black spots.

So what are these black spots on the glowing surface of the Sun?

Let's start with plasma. Solar plasma is a fully ionized gas. Plasma is called the “fourth state of aggregation substances", but this numbering is incorrect, because on the scale of the Universe, plasma is the most common state of matter. All stars are filled with plasma matter. Therefore, plasma represents not the fourth, but the first state of matter in nature.

Plasma and the free substances present in it electric charges, create a conducting environment for electric current, which determines its interaction with magnetic and electric fields.

Wikipedia says: “Due to the good electrical conductivity of plasma, the separation of positive and negative charges is impossible at distances greater than the Debye length and at times greater than the period of plasma oscillations.”

Here I must say that at high plasma densities and powerful convective flows, extended plasma ropes can arise, sometimes they are called “cords”, “strands”, “fibers”, “jets”, “magnetic tubes”, and now also “spicules” . These harnesses are real conductors of electrical currents. Powerful magnetic fields are formed around such bundles, which, in turn, build new electrical bundles. That is why in the photographs around the spots we see these ropes in the form of peculiar streaks that form magnetic helicities.

The spots visually seem black and cold to us, against a very bright background of the photosphere with an effective temperature of 5778 0 K, in fact their temperature is about 4500 0. The average depth of the spots is 500 km.

The interaction of such bundles (conductors) with each other leads to mutual spatial construction around an imaginary center. This is how it is formed black spot. The ionized substance from this center is literally “sucked out” into the bundles surrounding it. Which ultimately leads to the rapid expansion of black spots. Since convective plasma flows rise from the solar interior along radii, the formation of conductive electrical cords occurs in the radial direction. As the substance enters the area of ​​the stain, it immediately “disassembles” and is drawn into one or another bundle. Therefore, the radiation in the center of the spot decreases many times, and the temperature in this zone decreases accordingly, which leads to its invisibility.

In fact, the expansion of the spot occurs due to electromagnetic interaction parallel conductors with currents flowing in one direction. The attraction of current-carrying conductors to each other and located in a circle expands the space of this ring. At the first stage, the plasma ring cannot break due to replenishment by ascending plasma flows from the central regions of the Sun. As it expands, the electromagnetic forces in the center weaken, and convective flows begin to break through into the upper layers of the photosphere, wedging into plasma ropes that begin to collapse. This leads to the resorption of the stain.

Small spots can be formed by both ascending and descending plasma flows. In the case of a downward flow, the magnetic field of the spot will be opposite. Such spots cannot exist for a long time due to plasma pressure in convective flows emanating from the interior of the Sun. At the same time, spots formed by rising currents can reach enormous sizes and last for about a month.

Sunspots directly affect the climate and, as Chizhevsky argued, social processes.

Solar flares (solarquakes)

But it’s unlikely that the old astronomer
determines: “There is a storm in the sun.”
We can stare at the face to our heart's content,
with mouths open and eyes not squinting.

(Vladimir Vysotsky)

What is a solar storm (solar flare)? They write about it, they talk about it, they discuss it, they wait for it. But no one can say for sure what it is.

The only reliable fact is that flares do not occur without the presence of sunspots.

During a powerful flare, the flux of ultraviolet, x-ray and gamma radiation increases many thousands of times. Radioactive photon radiation reaches Earth eight minutes after the start of the flare. After a few tens of minutes, streams of charged particles arrive, and after two or three days clouds of electrons and protons reach the Earth.

The ozone layer and the entire atmosphere of the Earth are protected from lethal doses radiation, and the geomagnetic field is from charged particles. However, it is not possible to protect yourself 100% from hard radiation, so the threat from solar flares exists. Flares can damage satellites, irradiate astronauts, and affect airlines and power grids, so it is important to predict them and understand their nature.

“Solar flares typically occur where sunspots of opposite magnetic polarity interact, or more precisely, near the neutral magnetic field line separating regions of north and south polarity. The frequency and power of solar flares depend on the phase of the 11-year solar cycle."

A flare is a fountain of energy, with a temperature of up to 30 thousand degrees. This is a short-lived process that lasts about one minute. This information leads me to think about solar lightning. If the flash is powerful, then the process of plasma illumination can continue for a considerable time (tens of minutes, sometimes up to hours). It all depends on the scale of the grandiose phenomenon.

Since sunspots are unstable processes occurring in the photosphere, we can make the assumption that the flare is the result of unstable (transient) processes. At its core, a solar flare is powerful lightning! What does the most powerful mean? In this context I put the sum of elementary lightning bolts stacked in parallel. This huge flow of ionized particles in a single impulse closes with the opposite sign of the same particles ejected by the pressure of the Sun.

In fact, all these conductor bundles consist of individual lightning bolts, but against the general light background of the photosphere we observe them in the form of shades of lighter tones, pulsations.

The magnetic lines (see picture below), along which charged plasma particles rush, have a very small deviation and go upward. This tells you how large and strong the sunspot's magnetic field is. The image shows the beginning of the flare at the edge of the spot.

At the moment of such a lightning strike, a powerful gas pressure arises in the plasma, followed by a coronary plasma ejection and a sunquake.

A sunspot photographed from the front by the Hinode Solar Space Observatory. Plasma ejects upward along curving magnetic field lines.

Unlike earthquakes, which produce short bursts of waves on Earth, in the depths of the Sun, thanks to solar lightning, constant seismic noise and powerful sunquakes are created. But, since solar matter is not solid, but plasma, seismic waves quickly attenuate.

Solar flares are unique in their strength and power of release of thermal, kinetic, seismic and light energy from the Sun.

Moire graining of the solar surface

If oxygen were present in sufficient quantities on the Sun, then ash particles would constantly fall on our Earth, as during volcanic eruptions.

In this regard, I want to express one more original thought, which I will start with the question: What kind of granules (cells) are we observing from Earth through a telescope? At a sufficiently high magnification, the surface of the Sun appears to us in the form of moiré grain.

Granular structure of the solar surface, a dark spot in the center

The image clearly shows cells surrounded by dark boundaries of different shapes.

What are these granular cells and where do they come from?

Solar plasma is sometimes compared to boiling broth. This comparison is quite correct, because gives a visual model in miniature - the solar surface. When we prepare meat broth on the kitchen stove, then after boiling in the pan we observe rising currents of liquid, which different directions scatter the scum. If we take a photo of our broth from above, we can get a picture similar to the above photo.

Through experience with meat broth I lead the reader to the associative thought that there is scale on the boundaries of the solar granules! Solar scale is a product of combustion, including ash. As can be seen from the image, the granules have a lighter shade in the center, and darker closer to the border. This confirms the version of the comparison with the broth, i.e. the central part of the grains rises above the periphery, height differences can reach tens of kilometers, with an average granule diameter of 1000 km. This is such a sunny, seething and bubbling plasma broth.

The solar surface can be imagined even more clearly if you look at the tropical forest from above. Due to the different illumination of the tops of the tree crowns and the peripheral part of the crown, we can determine the difference in heights. Therefore, watching from above rainforests, you involuntarily catch yourself thinking that below is not a forest, but dome-shaped green earthen hills.

If we extend this analogy to the Sun, we can imagine that its surface consists of huge hills consisting of plasma of a brightly blinding color. These hills (granules) arise as a result of convective, upward flows, forming peculiar convective columns of plasma.

There are spots and flares on the Sun, there are sunquakes on the Sun! Spots and flashes can be observed visually, but tremors can only be detected using seismometers. Who and how can install devices on the Sun?

Sources

1. Quasineutrality, http://m.bankreferatov.ru/referats/.doc.html
2. Wikipedia, Solar flare, http://ru.wikipedia.org/wiki

Hinode is an artificial Earth satellite designed to study solar activity, magnetic field and radiation in the ultraviolet and X-ray ranges. On board there are optical and X-ray telescopes, as well as an ultraviolet spectrometer. The device was created through the efforts of Japanese, British and American engineers; was launched in 2006 from the Japanese Uchinoura spaceport.

Sunspots observed as areas of reduced luminosity on the surface of the Sun. Plasma temperature at the center sunspot reduced to about 3700 K compared to the temperature of 5700 K in the surrounding photosphere of the Sun. Although some sunspots They usually live no more than a few days; the largest of them can exist on the surface of the Sun for several weeks. Sunspots are areas of a very strong magnetic field, the magnitude of which exceeds the magnitude of the Earth's magnetic field by thousands of times. More often spots are formed in the form of two closely spaced groups, the magnetic field of which has different polarities. The field of one group has a positive (or northern) polarity, and the field of the other group has a negative (or southern) polarity. This field is strongest in the darkest part sunspot- his shadows. The field lines here extend into the surface of the Sun almost vertically. In the lighter part spots(its penumbra) the field is smaller and its lines are more horizontal. Sunspots are of great interest for research, since they are areas of the most powerful solar flares that have the strongest impact on the Earth.

Torches

Granules are small (about 1000 km in size) elements, similar to irregularly shaped cells, which, like a grid, cover the entire photosphere of the Sun, with the exception of sunspots. These surface elements are the upper part of convective cells going deep into the Sun. At the center of these cells, hot matter rises from the inner layers of the Sun, then spreads horizontally across the surface, cools, and sinks down at the dark outer boundaries of the cell. Individual granules do not last long, only about 20 minutes. As a result, the granulation network constantly changes its appearance. This change is clearly visible in the film (470 kB MPEG), obtained at the Swedish Vacuum Solar Telescope. The flows inside the granules can reach supersonic speeds of more than 7 km per second and produce sonic "booms" that lead to the formation of waves on the surface of the Sun.

Super granules

Supergranules have a convective nature similar to that of ordinary granules, but are noticeably larger in size (about 35,000 km). Unlike granules, which are visible on the photosphere with the ordinary eye, supergranules most often reveal themselves by the Doppler effect, according to which radiation coming from matter moving towards us is shifted along the wavelength axis to the blue side, and radiation from matter moving from us, shifts to the red side. Supergranules also cover the entire surface of the Sun and are continuously evolving. Individual supergranules can live for one or two days and have average speed currents are about 0.5 km per second. Convective plasma flows inside supergranules rake magnetic field lines to the edges of the cell, where this field forms a chromospheric grid.

There are several entertaining and rather instructive stories associated with sunspots, the first of which have come down to us from ancient times.

Ancient Greek astronomers considered the Sun to be flawless and ideal fireball, without any flaws. This point of view prevailed until the 17th century, at least in Europe. And far in the east, the Chinese, knowing nothing about the ideas of the Hellenes, even in the 1st century BC, described in their chronicles “birds” flying in front of the Sun. Europeans preferred not to think about sunspots at all, because they believed that if religion and philosophy declare the Sun to be perfect, then these “spots” could be either pairs passing between the Earth and the Sun, or planets.

During the reign of Charlemagne (8th century), the population of France saw a large black spot on the Sun for eight days. Scientists of that time declared that this was the planet Mercury. Their guess was not so stupid, since Mercury actually sometimes passes across the disk of the Sun, however, it crosses it in just a few hours.

With the invention of the telescope, sunspots were placed on the surface of the Sun, that is, where they actually are. The first report on the results of their observations was published in 1611 by the German astronomer Johann Fabritius. Around the same time, the Sun was observed through a telescope by mathematics professor (and part-time Jesuit) Christoph Scheiner, who, due to his belonging to the all-powerful Order, was unable to overcome the wall of Aristotle’s dictate about the purity of the Sun. Having received assurances from his church superiors that either his telescope or his vision were mistaken, the scientist, so as not to bring charges of terrible heresy upon himself, chose to retreat and obediently “forgot” about his research.

Galileo Galilei turned out to be less accommodating.

In 1612, commenting on Fabricius's observations in his letters, he described in detail irregular shape sunspots, their occurrence, decay, movement across the solar disk and, most importantly, he emphasized that spots are phenomena occurring on the surface of the Sun, but not bodies revolving around it.

After Galileo’s authoritative statement, scientists began an intensive study of the incomprehensible “smallpox” that spoils the face of our luminary. In 1613, Johannes Kepler suggested that “the variability of the spots indicates their cloudy nature, but ... terrestrial analogies can be of little help here.” In the 18th century, sunspots were considered dark peaks visible through the photosphere of the Sun during the “low tides” of luminous matter. Then the idea arose that sunspots were holes in the photosphere. This guess is close to modern ideas, but it is now known that sunspots are not holes in the photosphere, but colder, although quite bright, areas; they appear dark only in comparison with the surrounding extremely bright surface.

As for the periodicity of the appearance of sunspots, people made countless manifestations of earthly life directly dependent on them, primarily the weather, as well as hunger, pestilence, disease, war, that is, in fact, in this phenomenon they found a convenient “ scapegoat”, responsible for all sorts of misfortunes. Thus, the drought in Italy in 1632 was associated with the absence of sunspots. In those years when the face of the Sun was dotted with them, harvests were famous for their abundance, wheat prices fell, and trees grew faster.

In 1870, Yale University professor Elias Loomis made the connection Magnetic storms and the number of observed auroras with the periodicity of sunspots, which at that time no one could explain. Long years scientists remained completely unaware of how the Sun, located 150 million km from the Earth, could “shake” its magnetic field and ignite auroras... American cosmologist George Gamow in his book “The Star Called the Sun” was a little ironic notes that “the number of lynx skins purchased by the Hudson's Bay Company increases when there are many sunspots on the sun. This may be because during such periods the auroras are brighter and provide more opportunities for favorable hunting during the long polar nights.” Even more striking and strange was the coincidence of the maximum sunspots with the French and Russian revolutions, both world wars and the Korean conflict.

Of course, there are many subtle connections between solar and terrestrial phenomena. If the Sun is able to stimulate the growth of trees, then we cannot exclude the possibility that, as Shakespeare said, “there are tides in the activities of men” - tides with a periodicity of 11 years...

Professor A. Chizhevsky identified and convincingly substantiated the existence of 11 and 22-year solar cycles, being 50 years ahead of his time and ending up in the Gulag for this. He identified the connection between the occurrence of various social and biological catastrophes on Earth with the “sliding” 11-year cycle of solar activity, which significantly intensifies every 22 years. However, today there is no coherent theory explaining such interdependence. True, there are hypotheses. In particular, the hypothesis of Robert Bracewell from the University of California, who has been studying sunspot cycles for many years. More or less reliable data on sunspots have been available since about 1800. Based on these data, we can conclude that solar activity, measured by the “number of sunspots,” is different in different cycles, that is, the maximum of one 11-year cycle differs from the maximum of the next or previous one. Bracewell and a number of other scientists believe that there are other, longer cycles in the life of the Sun.

So what are sunspots, which, not without reason, are considered the most noticeable manifestation of activity? It turns out that these are the gaps between the granules that make up the photosphere of the Sun, only they have grown enormously. In contrast to the very bright photosphere, the spots appear dark, although they also glow, that is, they emit energy. The temperature of the middle part of the spot (the darkest and coldest) is about 4500°.

Sunspots appear as small, dark pores about two thousand kilometers across. Over the course of a few days, the spot increases in size and after two weeks reaches its maximum development. A typical sunspot is 50 thousand km across, which is 4 times the diameter of the Earth! Big spot can achieve significantly large sizes– up to 130 thousand kilometers. Large spots“live” for about three months, privates – for several days. Each spot has a dark central area, called the shadow, which is surrounded by a grayish cloud - the penumbra - as if it had a fibrous structure with traces of swirl around the center of the spot.

The most important feature of the spots is the presence of strong magnetic fields in them, reaching the greatest intensity in the shadow area. In general, the spot is a tube of magnetic field lines extending into the photosphere, completely filling one of several cells of the chromospheric grid. The upper part of the tube expands, and the lines of force in it diverge, like ears of corn in a sheaf.

For the most part, spots appear in groups, change, break up into separate parts, and disappear. Spots mainly appear near the equator of the Sun. The movement of sunspots occurs with at different speeds: the further from the equator, the slower the spot moves. This suggests that the Sun rotates not as a solid, but as a gaseous body. (Regions near the solar equator complete a revolution around their axis in 27 Earth days; near the polar zone - in 34.)

Largest sunspot

In 1947, a sunspot was observed with an area of ​​18 billion km 2.