Учебно-методическое пособие по чтению специальной литературы для студентов 1 курса физического факультета. Дроздова И.В - 18 стр.

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                                  The Solar Wind
The sun expends 240 tons of its total mass every minute. For a long time it was
considered to emit light and heat energy only. But later on it was discovered that it
emits into space also radiowaves. The flights made outside the Earth’s atmosphere
made it possible to obtain even more data on the Sun’s distant ultraviolet and X- ray
irradiation.

In January 1959 the Soviet "lunniks" discovered the solar wind-movement of masses
not of air but of plasma particles. This wind is produced not by the Sun itself, but by
its corona-the silvery pearl-like sphere that stretches tens of millions of kilometres
outside the solar disk.

The Earth is known to be a colossal magnet and the solar wind influences greatly the
shaping of its magnetosphere. On the solar side it is pressed against the Earth and on
the opposite side it spreads for many dozens or even hundreds of millions of
kilometres, forming a long magnetic train. Any disturbances of the solar magnetic
field cause disturbances in the magnetic field of the Earth, manifested as magnetic
storms.

Under the Intercosmos programme a number of sputniks were launched with the
mission of gathering data on solar activity. The instruments aboard the sputniks help
to understand the mechanism of short-wave irradiation during solar flares and other
active processes in the Sun and also the impact of this radiation upon the density and
composition of the upper layers of the terrestrial atmosphere. This, in its turn, has
served as a basis for building up a more precise theory of ionospheric disturbances.

Research was continued aboard the Prognoz automatic probes. The orbits of the
probes are "elongated" towards the Sun and in the apogee reach 200,000 km. This
allows to observe solar wind, undisturbed by the terrestrial magnetic field and to
study the so called shock waves.

The matter is that the solar wind particles move away from the Sun at a steadily
increasing velocity-they are being pushed by a hotter gas. The velocity reaches that of
sound long before the wind comes near the Earth. When such a supersonic plasma
flow hits our planet, a shock wave is produced, the same as that produced when a jet
plane travels at supersonic speed in the atmosphere.

The density, temperature and velocity of the solar wind can greatly exceed the
average parameters with the appearance of solar flares when tremendous masses of
plasma are discharged from the solar corona. Their record measurements were
registered by the Prognoz sputnik as far back as 1972. The wind velocity reached
2,000 km per sec. And the formation of other shock waves was observed in the
interplanetary space.