Classical two-ribbon flare models explain the evolution of these type of events after a filament ejection, and the posterior reconnection of the magnetic field lines opened in this process. These models do not take into account the flare onset phase. We analyze the X-ray data obtained by the Hard X-Ray Imaging Spectrometer (3.5 - 30 keV) in two-ribbon flares. During the flare onset phase, we obsreve the presence of coral plasma at 10⁷ K surrounding the active region filament. Our observations are in good agreement with the predictions of recent two-ribbon flares circuit models.Asociación Argentina de Astronomí
