A Multiwavelength Analysis of the Long-duration Flare Observed on 15 April 2002

Abstract

We present a multiwavelength analysis of the long-duration flare observed on 15 April 2002 (soft X-ray peak time at 03:55 UT, SOL2002-04-15T03:55). This flare occurred on the disk (S15W01) in NOAA 9906 and was observed by a number of space instruments including the Extreme-Ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory (SOHO/EIT), the RESIK spectrometer onboard the Coronas-F spacecraft, and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We have performed a complex analysis of these measurements and studied the morphology and physical parameters characterizing the conditions in flaring plasmas. The 195 Å SOHO/EIT images have been used to study evolution of flaring loops. Analysis of RHESSI data provided the opportunity for a detailed analysis of hard X-ray emission with 1 keV energy resolution. We have used Geostationary Operational Environmental Satellite (GOES) observations for isothermal interpretation of the X-ray measurements. Temperature diagnostics of the flaring plasma have been carried out by means of a differential emission measure (DEM) analysis based on RESIK X-ray spectra. The DEM distributions were calculated based on two methods: Withbroe–Sylwester (WS) and differential evolution (DE). Both of the approaches provided similar results. We obtained two-component DEM distributions independent of the evolutionary flare phase. We found that the amount of energy of thermal plasma for this flare is of the order of 1030 ergs. The values obtained by assuming an isothermal plasma model are lower than those determined from the differential emission measure distributions.