EIT and TRACE responses to flare plasma |
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Durgesh Tripathi Submitted: 2006-11-06 09:38
Aims: To understand the contribution of active region and flare plasmas to the 195 A channels of SOHO/EIT (Extreme-ultraviolet Imaging Telescope) and TRACE (Transition Region and Coronal Explorer).
Methods: We have analysed an M8 flare simultaneously observed by the Coronal Diagnostic Spectrometer (CDS), EIT, TRACE and RHESSI. We obtained synthetic spectra for the flaring region and an outer region using the differential emission measures (DEM) of emitting plasma based on CDS and RHESSI observations and the CHIANTI atomic database. We then predicted the EIT and TRACE count rates.
Results: For the flaring region, both EIT and TRACE images taken through the 195 A filter are dominated by Fe XXIV (formed at about 20 MK). However, in the outer region, the emission was primarily due to the Fe XII, with substantial contributions from other lines. The average count rate for the outer region was within 25% the observed value for EIT, while for TRACE it was a factor of two higher. For the
flare region, the predicted count rate was a factor of two (in case of EIT) and a factor of three (in case of TRACE) higher than the actual count rate.
Conclusions: During a solar flare, both TRACE and EIT 195 A channels are found to be dominated by Fe XXIV emission. Reasonable agreement between predictions and observations is
found, however some discrepancies need to be further investigated.
Authors: D. Tripathi, G. Del Zanna, H. E. Mason, C. Chifor
Projects: SoHO-EIT,SoHO-CDS,TRACE
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Publication Status: Accepted for publication in A&A letters
Last Modified: 2006-11-06 09:46
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