Análisis temporal de la emisión en altas energías durante fulguraciones solares

MANDRINI, C.H.; ROVIRA, M.G.; MACHADO, M.E.

San Juan

Congreso; 41 Reunión Anual de la Asociación Argentina de Astronomía; 1997

Asociación Argentina de Astronomía

It is well known that the hard X-ray (HXR) emission from solar flares is caused by the energization of electrons in the energy dissipation region or regions. Irrespective of how this dissipation occurs, it has been known for many years that the energy contained in these particles represents a major fraction of the total flare energy. It can then be assumed that any modulation observed in the recorded HXR emission must be related to a modulation in the energy release process. This was recognized by van Beek, de Feiter and de Jager (1974, Space Res. 14, 447) and by de Jager and de Jonge (1978, Solar Phys. 58, 127) who, from the analysis of the TD1-A spacecraft data, proposed that HXR bursts could in general be decomposed into a number of short-lived spikes of duration ranging from a few seconds to a few tens of seconds. They called these spikes ``elementary flare bursts´´ (EFBs) and suggested that they represented the fundamental timescales of flare energy release. In this work we analyse the high temporal resolution (64 ms, 15< = E <= 300 keV) data recorded by the Burst and Transient Source Experiment (BATSE), aboard the Compton Gamma Ray Observatory, using the Driscrete Wavelet Transform Method. We study more than a dozen of events of different importance and temporal evolution. Our results show that most of the events present fine temporal fluctuations in the 0.5 to 1 s range. While a few bursts just show a gradual rise and fall structure with no spikes. No case was found in which significant <= 0.2 s spikes were observed. On the other hand, a ``slow´´ (seconds to tens of seconds) modulation in the HXR intensity, consistent with EFBs, can also be detected in the BATSE records, particularly when their time resolution is degraded to >= 1 s. We have also found several examples where spikes in the lower energy band precede spikes in the higher energy range, what is consistent with HXR emission by magnetically trapped particules.