Life on Earth is entirely dependent on the processes occurring on the Sun, therefore scientists are constantly observing the star. Its surface is never calm, but over the past two decades, researchers have noted a slight decrease in solar activity. Can the Sun cool down or, conversely, suddenly explode.
Typical yellow dwarf
For astronomers, the Sun is an ordinary star, a yellow dwarf. The age is five billion years. It is now located approximately in the middle of the main sequence on the Hertzsprung-Russell diagram showing the evolution of stars.
“Yet the Sun is unique. Thanks to the peculiarities of its structure and the location of the Earth relative to it, life arose, says Vladimir Bogod, Doctor of Physical and Mathematical Sciences, head of the St. Petersburg branch of the Special Astrophysical Observatory of the Russian Academy of Sciences.
His group is studying the luminary using the RATAN-600 radio telescope at centimeter and decimeter radio waves, located in the mountains of the North Caucasus. This is the most convenient range for studying the corona radiation of such a large, bright and close object.
In the most general view, the Sun is a constantly burning hydrogen ball. Nuclear reactions take place inside at temperatures in excess of 14 million Kelvin. Energy in the interior is transmitted by radiation and absorption of photons (radiant transfer). Closer to the surface, the substance cools down, the convection zone and the visible photosphere with a temperature of 5800 Kelvin begin. By mixing, the plasma generates supergranules that reach half the radius of the Sun.
Magnetic fields inhibit the exchange of energy between highly ionized plasma particles, as a result of which dark areas - spots appear in the photosphere.
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Above the photosphere is a chromosphere only about thirty thousand kilometers thick and a temperature of ten thousand Kelvin. It is covered by a transition layer of one hundred kilometers, followed by a crown. The temperature in it jumps to two million, and above the spots - to twenty million. The plasma density, on the contrary, decreases by two orders of magnitude.
In the corona above the spots, conditions are created for the transition of magnetic energy into the energy of powerful flares.
“In this case, the structure of the magnetic fields is simplified, collapses and shoots plasma into the surrounding space, as if from a slingshot,” explains Bogod.
How magnetic fields are converted into energy is a fundamental question that determines the efficiency of tokamak-type fusion reactors. After its solution, humanity will find another reliable source of energy.
Where the stains go
The corona provides information on solar activity. Analyzing it, scientists are looking for harbingers of powerful flares.
“Flares are the spontaneous production of a large number of electrons and protons, in fact, explosions that eject high-energy plasma. Having reached the Earth, a powerful flash generates magnetic storms, auroras in the atmosphere. By analyzing the radio emission spectra, we can determine the precursors of flares in two or three days,”says Vladimir Bogod.
According to estimates made in his group, the probability of a supernova-like explosion of the Sun is very small - nothing threatens him. When the hydrogen inside burns out enough, the Sun will begin to expand - the Earth, of course, will burn out - and then turn into a white or black dwarf. But before that, there are still billions of years.
It's much more important to keep track of your activity cycles. Their maximum is marked by the minimum number of spots on the sun's surface. The shortest cycles are eleven years. Observations show that for the second consecutive cycle, the activity of the Sun decreases, the number of spots decreases, and this affects the climate. Similar processes in the 17th century led to a noticeable cooling in Europe (Maunder minimum). A possible reason is the interaction of cycles of different frequency.
A decrease in the activity of the Sun is fraught with another problem - the penetration of cosmic rays onto the Earth, carrying high-energy heavy atomic nuclei and particles. This affects not only the climate, but all living things.
The closest star to us, the Sun, is an excellent tool for studying distant space objects. This is a kind of standard and yardstick for other stars, which cannot yet be investigated as thoroughly as the Sun.
Tatiana Pichugina