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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