Quasibernstein modes in preflare atmosphere of Solar active region: the second harmonic generation

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Space and Atmospheric Physics
1Kryshtal, AN, 2Gerasimenko, SV, 1Voitsekhovska, AD
1Main Astronomical Observatory of the NAS of Ukraine, Kyiv, Ukraine
2Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
Kosm. nauka tehnol. 2010, 16 ;(6):40-50
https://doi.org/10.15407/knit2010.06.040
Publication Language: Russian
Abstract: 
The generation of the second harmonic during the development of the corresponding instability is investigated for the pure electron oblique Bernstein modes modified by taking into account Coulomb collisions and existence of the weak large-scale electric field in the post-flare loop. We propose to name such modes as quasibernsteinian ones. It is supposed that the main characteristics of magnetoactive plasma at the foot-points of the loop structures, which correspond to the “lower-middle” chromosphere of an active region (AR), are determined through the semiempirical model for the solar atmosphere of Fontenla‒Avrett‒ Loeser (FAL).
             It is been demonstrated that the use of this model instead of the models of Machado‒Avrett‒Vernaz-za‒Noyes (MAVN) and Vernazza‒Avrett‒Loeser (VAL) used before leads to considerable changes of the instability threshold values of subdreicer electric field amplitudes and boundary values of the perturbation wavelength. Microwave emission in the centimetre-millimetre interval can appear under favourable conditions due to the coalescence of two quasibernsteinian harmonics with next formation of electromagnetic wave. 
Keywords: loop structures, magnetoactive plasma, quasibernstein modes
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