Solar wind

The concept solar wind was introduced into astronomy in the late 40s of the 20th century, when the American astronomer S. Forbush, measuring the intensity of cosmic rays, noticed that it decreases significantly with increasing solar activity and quite falls sharply during magnetic storms.

The concept solar wind was introduced into astronomy in the late 40s of the 20th century

This seemed rather strange. Rather, you could expect the opposite. After all, the Sun itself is the supplier of cosmic rays. Therefore, it would seem, the higher the activity of our daylight, the more particles it should throw into the surrounding space.

It remained to be assumed that the increase in solar activity affects the earth's magnetic field in such a way that it begins to deflect the particles of cosmic rays-throw them away.

Then it arose that the culprits of the mysterious effect are the fluxes of charged particles, escaping from the surface of the Sun and penetrating the space of the solar system. This peculiar solar wind cleanses the interplanetary medium, "sweeping out" of it particles of cosmic rays.

In favor of this hypothesis, the phenomena observed in comets also spoke. As is known, comet tails are always directed from the Sun. At first, this circumstance was associated with the light pressure of the sun's rays. However, it was found that only light pressure can not cause all phenomena occurring in comets. Calculations have shown that for the formation and observed deviation of the comet tails, the action of not only photons but also particles of matter is necessary.

Strictly speaking, the fact that the Sun throws out the streams of charged particles - corpuscles, it was known before. However, it was assumed that such flows are episodic. But the comet tails are directed to the side opposite to the Sun, always, and not only during periods of increasing solar activity. Hence, and the corpuscular radiation that fills the space of the solar system must exist constantly. It increases with increasing solar activity, but it always exists.

Thus, the solar wind continuously blows out the near-sun space. What does this solar wind consist of, and under what conditions does it arise?

The outermost layer of the solar atmosphere is the "crown". This part, the atmosphere of our daylight, is extremely rarefied. But the so-called "kinetic temperature" of the corona, determined by the velocity of the particles, is very large. It reaches a million degrees. Therefore coronal gas is completely ionized and is a mixture of protons, ions of various elements and free electrons.

Recently a message appeared that the solar wind has helium ions in its composition. This circumstance sheds light on the mechanism by which the charged particles emit from the surface of the sun. If the solar wind consisted only of electrons and protons, it could still be assumed that it is formed by purely thermal processes and is something like a vapor formed above the surface of boiling water. However, the nuclei of helium atoms are four times heavier than protons and, therefore, it is unlikely that they can be ejected due to evaporation. Most likely, the formation of the solar wind is associated with the action of magnetic forces. Departing from the Sun, clouds of plasma, as it were, carry with them magnetic fields. It is these fields that serve as that kind of "cement", which "holds together" particles with different masses and charges.

Observations and calculations carried out by astronomers have shown that as the distance from the Sun decreases, the density of the corona gradually decreases. But, it turns out, in the area of the Earth's orbit, it still differs markedly from zero. In other words, our planet is inside the solar atmosphere.

If near the Sun the corona is more or less stable, then as the distance increases, it tends to expand into space. And the farther from the Sun, the higher the speed of this expansion. According to the calculations of the American astronomer E. Parker, already at a distance of 10 million km the coronal particles move with velocities exceeding the speed of sound.

Thus, the conclusion suggests that the solar corona is the solar wind that blows the space of our planetary system.

These theoretical conclusions were fully confirmed by measurements on space rockets and artificial satellites of the Earth. It turned out that the solar wind exists always and near the Earth - "blowing" at a speed of about 400 km/sec.

How far is the solar wind blowing? With theoretical considerations, in one case it turns out that the solar wind is already falling in the area of Saturn's orbit, in the other, that it exists at a very great distance beyond the orbit of the last planet of Pluto. But this is only theoretically the extreme limits of the possible spread of the solar wind. Only the observations can specify the exact boundary.