Multi-wavelength study of a strong impulsive solar limb flare on 2002 August 3 S. Gburek a, * , J. Sylwester a , B. Sylwester a , B.R. Dennis b , K.J.H. Phillips c a Space Research Centre, Polish Academy of Sciences, Ul. Kopernika 11, PL-51-622 Wroclaw, Dolnasla, Poland b NASA Goddard Space Flight Center, Code 682,Greenbelt, MD 20771, USA c National Research Council Senior Research Associate, NASA Goddard Space Flight Center, Code 612, Greenbelt, MD 20771, USA Received 28 October 2004; received in revised form 25 May 2005; accepted 25 May 2005 Abstract We made a detailed study of the impulsive solar flare of GOES class X1.0 which occurred near the west limb on 2002 August 3, peak time 19:07 UT. There is particularly good data coverage of this event, with simultaneous observations in EUV, soft and hard X-rays available. We used TRACE 171 A ˚ images to study the morphology and evolution of this event. Soft X-ray spectra in the wavelength range 3.34–6.05 A ˚ measured by the RESIK Bragg crystal spectrometer on CORONAS-F were used for determination of the evolution of the flare plasma temperature. Data from the RHESSI instrument were used to investigate properties of the higher-temperature plasma during the flare. Ó 2005 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Solar flares; X-ray; EUV 1. Introduction In what follows we focus on the analysis of properties of a major solar flare (GOES class X1.0) which occurred on 2002 August 3. The entire flare has particularly good data coverage, with EUV images (TRACE telescope: Handy et al., 1999), 4–300 keV X-ray images and spectra (RHESSI: Lin et al., 2002), and soft X-ray spectra (RE- SIK: Sylwester et al., 2005). We used data from the above mentioned instruments to investigate the event evolution, location of EUV/X-ray emission sites, and their spectroscopic properties in different flare phases. 2. RHESSI and TRACE flare observations The event site was located in NOAA 0039 active region located at S15W70 with c magnetic configuration. There were many active regions on 2002 August 3, but inspection of EIT full disk images as well as TRACE and RHESSI images show no other significant solar activity apart from the analyzed event. The flare soft X-ray flux started to rise in GOES channels at 18:58 UT. Due to high RHESSI sensitivity it was possi- ble to detect a small increase in soft X-ray emission at the flare site 2 min earlier, at 18:56 UT. In the TRACE 171 A ˚ energy band the emission rise occurred 2 min later relative to GOES increase. There was a very rapid rise of the GOES flux and in the count rates of the soft X-ray channels (3–25 keV) of RHESSI, reaching a peak at about 19:07 UT. Subsequently, the softer GOES and RHESSI fluxes began to decrease to a level slightly high- er than the pre-flare level. A similar time-line is observed for TRACE 171 A ˚ flux. The situation was somewhat different at higher energies (25–300 keV) observed by RHESSI. In this case, the emission is in the form of several sharp impulsive bursts over the period 19:04–19:08 UT. This is evident in 50–100 keV and 0273-1177/$30 Ó 2005 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2005.05.094 * Corresponding author. E-mail address: sg@cbk.pan.wroc.pl (S. Gburek). www.elsevier.com/locate/asr Advances in Space Research 35 (2005) 1728–1731