Asymmetry time dependence of the X-ray footpoints emission in a solar
flare observation
Marek Siarkowski1 and Robert Falewicz2
1
Space Research Centre, Polish Academy of Sciences, 51-622 Wroclaw, ul.
Kopernika 11, Poland
2
Astronomical Institute of Wrocław University, 51-622 Wrocław, ul. Kopernika
11, Poland
Abstract
In our paper we analyse hard and soft X-ray observations (SXT and HXT
YOHKOH satellite) for X5.3 class flare of 25 August 2001. Most
prominent structures of this flare are: fast (450 km/sec), hard (up to 90
keV) and compact X-ray moving feature, two clear footpoint sources and
loop-top emission between them. Often observed asymmetry in footpoint
hard X-ray emission is usually interpreted as an effect of the difference
in magnetic field strength or the field divergence at the footpoints
(Sakao et al. ,1996; Kundu et al. , 1996; and Aschwanden et al. ,1999).
New observations indicate also the presence of time variation in this
asymmetry (Alexander and Metcalf, 2002). These data with strong X-ray
flux allow image synthesis each 0.5 – 1 sec during a few minutes. During
this time we have observed clear, quasi-periodical changes in the
asymmetry of the observed footpoints. Traditional interpretation
indicates the existence of strong magnetic field oscillations or
movements of the footpoints location in the presence of strong magnetic
gradient. Our analysis indicates rather the differences in the injection
conditions in each of loop leg. We find this interpretation consistent with
the existence of the turbulent loop-top kernel (Jakimiec et al. 1998).