To the problem of possibility of appearance of preflare current sheets in the chromosphere of active region

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. 2012, 18 ;(3):52–60
Publication Language: Russian
Conditions of the appearance and development of ionacoustic instability in preflare plasma of a loop structure in solar active region have been investigated. The investigations were conducted in the framework of a semiempirical FAL (Fontenla-Avrett-Loeser) model of solar atmosphere. Subdreicer electric field together with parallel to it magnetic «kilogauss» field are supposed to be present in the region of current loop near its foot-point. It is shown that small-scale ion-acoustic instability with low threshold of excitation in the units of amplitude of subdreicer field can arise in investigated region before the phase of «pre-heating». It has been demonstrated that in the framework of the concept used, reducing of the threshold of excitation of instability is possible only when the degree of non-isothermality of plasma increases.
Keywords: ion-acoustic instability, solar active region, subdreicer field
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