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The necessary physical conditions for development of the ion-acousticinstability in the chromospheric part of a flaring loop current circuit areinvestigated. Two possible scenarios have been studied. First, we considerthat pre-flare loop plasma with the large-scale sub-Dreicer electric fieldhas a classical Coulomb conductivity and, second, when anomalous resistanceappears due to saturation of Bernstein turbulence. The Fontenla-Avrett-Loeser (FAL) model of the solaratmosphere was used to describe the pre-flare plasma. We have shown thatinvestigated instability can grow and develop either in the presence of theCoulomb conductivity or saturated Bernstein turbulence. We demonstrate thatin the case of small-scale instability, the threshold value for the degree ofnonisothermality is high and, therefore, cannot be reached by inclusion ofthe ordinary Joule heating. The ion-acoustic instability can develop at thepre-flare loop footpoints provided the electrons are more than 10 timeshotter than the ions there

The ion-acoustic instability in the pre-flare plasma near the loop footpoints at solar active regions