Astronomical School’s Report, 2017, Volume 13, Issue 2, Pages 68–80
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UDC 523.98

Sources of solar energy and interplanetary magnetic field

Krivodubskij V.N.

Astronomical Observatory of Taras Shevchenko National University of Kyiv, Observatorna str. 3, 04053 Kyiv, Ukraine


The sources of energy of solar activity are analyzed. The primary source of solar energy is the core of the Sun, where as a result of the reactions of thermonuclear fusion, energy is released in the form of γ-quanta and neutrino particles that propagate outward. When approaching the surface due to the fall in temperature and the increase in the opacity of the substance, the fully ionized solar plasma, from certain depths, passes into the state of partial ionization. As a result, a Schwarzschild criterion of the emergence of a convective energy transfer due to hydrodynamic motions begins to run at a distance of 0.3 solar radius from the surface. Above this boundary lies a layer of convective turbulence, in which energy is transferred mainly by a moving substance, and not by radiation. It is called the convective zone. Ultimately, the part of the radiant energy transferred to the surface gives the opportunity to observe the Sun in different wavelength ranges. While the second part of the upward energy, which is due to convective motions, will manifest itself at the photospheric level in the form of granulation movements of various scales accessible for observation. However, part of the flow of energy coming from the interior of the Sun, accumulates and is carried upwards in the “magnetic form”. An important specific property of this highly effective mechanism of magnetic energy transfer is its significant variations in time, which are manifested in cyclic changes of the majority of phenomena generated by magnetic fields, called solar activity. The specificity of this energy transfer is manifested in the non-stationary flare conversion of magnetic energy into heat, as well as in the kinetic energy of accelerated particles and macroscopic (coronal) plasma emissions. The role of the landfill, where the main processes responsible for cyclic manifestations of solar activity originate, is played by the convective zone. In the depths of the convective zone, as a result of the dynamo mechanism, some of the kinetic energy of the hydrodynamic motions (differential rotation and gyrotropic turbulent convection) is converted into magnetic energy during the solar cycle, thereby strengthening the weak magnetic field of the Sun of relic origin. The global magnetic field generated in depths is transferred to the solar surface due to its magnetic buoyancy. Surface magnetic structures change the state of the Sun's atmosphere, cause an irregular part of the radiation and serve as a source of powerful non-stationary phenomena in the outer atmospheric layers (photosphere, chromosphere and corona). The modern concept of such phenomena as hot solar corona, solar wind and interplanetary magnetic field that form space weather in the interplanetary space is reviewed. The contribution of the “Kiev coronal school” of Vsekhsviatskij S.K. to the development of the concept of the dynamic corona of the Sun is noted.

Keywords: Sun; radiation; convection; magnetic energy; space weather; corona; solar wind; interplanetary magnetic fields


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