Small-scale instabilities in the preflare loop plasmas in active regions

1Kryshtal, AN, 1Gerasimenko, SV, 2Voitsekhovska, AD
1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
2Main Astronomical Observatory of the NAS of Ukraine, Kyiv, Ukraine
Kosm. nauka tehnol. 2007, 13 ;(Supplement1):109-111
Publication Language: Russian
Physical conditions for rise and development of different types of plasma instabilities at the origin of a flare process were studied. The main reason of the instability is the summary action of three factors, namely, the existence of quasi-static large-scale electric field in a loop, the influence of the pair Coulomb collisions as well as the influence of the inhomogeneities of plasma temperature and density. The model of interacting magnetic fluxes of Heyvaerts–-Priest–Rust and the model of the loop equivalent current circuit of Stepanov–Zaitsev were used as the models of a flare process. The process begins with the rise of the first instability having the lowest threshold of excitation, and the initial stage of the process finishes with the appearance of the current layers. It is shown that adiabatically slow growth of the amplitude of subdreicer electric field in a loop corresponds to the distinct order of the appearance of the definite type of instabilities at the various parts of current circuit. Our results can be considered as the necessary condition for the short-time prediction of the flare in the loop structure.
Keywords: excitation, flare process, instability
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