Ejection during the solar flare in NOAA 8739 active region on 26 October 1999

Abstract

We analysed a huge ejection of the matter along an extended system of the magnetic loops in NOAA 8739 active region on 26 October 1999. The study was made using high cadence ground-base Multi-Channel Double Pass Spectrograph Hα spectra, TRACE 171 Å and 195 Å ultraviolet, Yohkoh Soft X-ray Telescope images and INTERBALL RF15-I 2–30 keV photometer X-ray measurements. We found the following: The ejection was associated with a C6.5 GOES class solar flare with precursor. The ejection consisted of two distinct stages. The cool matter, visible in Hα line, was ejected at first, after the precursor but before the impulsive phase of the flare. The hotter plasma, visible in UV lines, was ejected two minutes later just before the impulsive phase. The kinetic energy of the ejected Hα matter was relatively low and only a fraction of the matter was transferred to the opposite footpoints of the loop system. The significant part of the matter fell back into the ejection region. A new magnetic field emerged from below the chromosphere in the flaring region just after the ejection. The field was visualised as a co-linear system of the dark loops and fibrils. They then merged with the adjacent filament, extending its length. All flare-like Hα brightenings (with flat or reversed profiles) in the whole active region occurred simultaneously or just after the very distinct increases of the X-ray signal recorded in the 10–15 keV channel. The increases of the signals recorded in the softer channels were much less distinct or did not occur in all. The profiles of the Hα line emitted by the flaring kernels were significantly shifted to the red.