Conditions for the Excitation of Type I Solar Bursts

Geomagnetism and Aeronomy. 2023. Vol. 63. No. 7. P. 910–915.

P.A.Bespalov, O.N.Savina

According to modern concepts, Type I noise storms in the meter wavelength range (30–400 MHz), consisting of a large number of narrow-band short bursts, are excited in the rarefied solar corona. These radiations are characterized by a high brightness temperature and circular polarization. Despite many advances in theory and confidence that the mechanism of radiation formation is coherent, there is currently no generally accepted understanding of the nature of Type I noise storms. In this paper, we show that many important properties of radiation can be explained as a result of the BPA (beam-pulse-amplifier) mechanism in a rarefied magnetized plasma with energetic electrons. Short noise electromagnetic pulses with a suitable carrier frequency, with circular polarization and wave normal angle can be amplified in the plasma layer at an extremely high rate, which is characteristic of quasi-hydrodynamic type instability. When this mechanism occurs, high energy and the rate of change in the spectral forms of radiation can take place even in the absence of a noticeable anisotropy of the distribution function of energetic electrons.

Keywords: solar corona, солнечные вспышки, солнечная корона, energetic electrons, Type I noise storms, solar burts, rarefied magnetized plasma, шумовые бури первого типа, замагниченная разреженная плазма, энергичные электроны