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In this study we discuss the excitation of low frequency plasma waves in thelower-middle chromosphere region of loop footpoints for the case when theplasma can be considered in a pre-flare state. It is shown, that among theknown semi-empirical models of the solar atmosphere, only the VAL (F) modeltogether with a particular set of basic plasma parameters and amplitudes of theelectric and magnetic fields supports generation of low frequency waveinstability. Our results show that it is possible to predict the onset of theflare process in the active region by using the interaction of kinetic Alfvenand kinetic ion-acoustic waves, which are solutions of the derived dispersionequation. The VAL (F) model allows situations when the main source of theaforementioned instability can be a sub-Dreicer electric field and drift plasmamovements due to the presence of spatial inhomogeneities. We also show that thegeneration of kinetic Alfven and kinetic ion-acoustic waves can occur both, inplasma with a purely Coulomb conductivity and in the presence of small-scaleBernstein turbulence. The excitation of the small amplitude kinetic waves dueto development of low threshold instability in plasma with relatively lowvalues of the magnetic field strength is also discussed.

Generation of low-frequency kinetic waves at the footpoints of pre-flare coronal loops