Slow X-Ray Bursts and Chromospheric Flares with Filament Disruption

The data from OGO-5 and OSO-7 X-ray experiments have been analyzed to study six chromospheric flares with filament disruption associated with slow thermal x-ray bursts. Filament activation accompanied by a slight x-ray enhancement precedes the first evidence of Hα flare by a few minutes. Rapid increase of the soft X-ray flux is accompanied by a sudden brightening of the filament when viewed on-band Hα. Thereafter the bright chromospheric strands reach their maximum brightness with maximum X-ray flux. Any plateau or slow decay phase in the x-ray flux is accompanied by a quieting in filament activity and even by filament re-appearance. The height of the disrupted prominence is proportional to the soft X-ray flux for the August 3, 1970 limb occulted event. Analysis of the X-ray bursts on 2220 UT June 23, 1972 gives a 'cool' maximum temperature of 12.5 x 10⁶ K maximum emission measure of 40 x 10⁴⁷ cm⁻³. Conduction is shown to be a more efficient cooling mechanism of the hot flare plasma than radiation. Initial heating probably occurs in the vicinity of the filament and filament activation may visualize some magnetic field changes which heat up the X-ray emitting plasma.