On the possibility of the development of longitudinal wave instabilities on the background of the small-scale Bernstein turbulence in preflare chromosphere of a solar active region

The process of origination and development of instabilities of the longitudinal waves of two types, namely, low-frequency ion-acoustic and high-frequency (“electronic”) Langmuir waves, in the preflare atmosphere of an active solar region are studied. The area under study is located at the chromospheric part of the flare loop near its footpoint. A weak large-scale electric field of flaring loop is the main source of these instabilities. The velocity of an electronic flow in the preflare plasma is supposed to be much lower than thermal electron velocity. Instability development is considered against the background of small-scale Bernstein wave turbulence, which exists in the preflare plasma and has an extremely low threshold of excitation. The necessary conditions for the instability origination and development, as well as the boundary values of the main plasma and wave perturbation parameters, are calculated.