Solar activity

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Solar activity

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Solar activity

The Sun is the closest star to us, and a regular object in our Galaxy. Solar activity manifests itself, primarily, in solar flares - episodic explosive energy release in the form of electromagnetic radiation and high energy particles (electrons and protons). The nature of the flares is related to cyclic variations of global and local magnetic fields in the atmosphere of the Sun. Observations of solar radio-frequency emission in the microwave range with RATAN-600 allow one to determine the parameters of the plasma and therefore, measure magnetic-field strengths in the chromosphere and corona of the Sun. Powerful flares originate in these layers of the solar atmosphere, along with coronal mass ejections, whereby clouds of plasma cause geomagnetic storms upon reaching the Earth's ionosphere. As a result of mixing of matter and non-uniform rotation of the Sun, magnetic field lines periodically "emerge" from underneath the photosphere in the form of visual-range sunspots. When considering other ranges - X-rays, ultraviolet, radio - we see that the emerging magnetic tube forms a three-dimensional loop, which can intertwine, creating bundles of strong magnetic fields, and form complex structures with other loops. Such formations are called active regions. When the loops interact with each other, a reconnection of magnetic field lines occurs, accompanied by a release of accumulated magnetic energy, and, as a result, a simplification of the magnetic structure of the region, its break-up, and consequent disappearance of the spot. Active regions at the solar surface "live" for several hours to several months. The full activity cycle lasts for 11 years, whereas the Sun rotates about its axis once every 27 days. In comparison, a large flare lasts for only a few minutes, but the preliminary stage of the flare - the increase of the complexity of the magnetic structure, the emergence of new magnetic tubes - takes up to three days. During this time, one can predict solar flares by the typical magnetic-field configuration in the photosphere, the characteristic spectra, and the distribution of intensity and polarization of microwave radiation. The interest in solar activity and the geomagnetic storms that it causes is due to the fact that the latter can affect the well-being of meteosensitive people, and also cause various industrial problems (radio communication interference, exposure of astronauts during space walks, transport and commercial infrastructure, agriculture, etc.).

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Last update: 26/03/2014