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Session 1 - Chromosphere, Corona, Flares.
Display session, Friday, June 27
Ballroom B, Chair: Charles Kankelborg

[1.69] Movies of flares observed by YOHKOH/HXT

J. R. Lemen, D. Alexander, T. R. Metcalf, S. L. Freeland, N. Nitta (LMSAL)

The Yohkoh Hard X-ray Telescope (HXT) has revealed new information about solar flares by providing high spatial resolution (5 arcsec) images in four energy bands covering 14 to 99 keV. The comparison of images obtained in hard X-rays with those obtained with the Yohkoh Soft X-ray Telescope (SXT) has led to important interpretations of flare heating mechanisms (e.g., Masuda et al, 1994, Nature, 374, 495). The HXT images are formed by reconstructing data obtained from 64 detectors located behind a bi-grid modulation pattern. Reconstruction algorithms using Maximum Entropy and PIXON methods have been successfully applied to the HXT data (Alexander and Metcalf, 1997, ApJ, submitted). At the recent HXT Coordinated Data Analysis Workshop held in January 1997, new calibration data for the response of the grids were incorporated and an error in the application of the reconstruction algorithms was identified and corrected (see Kosugi et al 1997 in these proceedings). As a result, it is now possible to reconstruct the HXT images semi-automatically to produce quick-look movies. We are in the process of generating movies for all flares obtained with the HXT using an MEM reconstruction. The automated procedure selects time intervals on the basis of the count rate statistics. We present a selection of reconstructed images and movies from this on-going project. We expect that the ability to view easily time sequences from many flares observed with the HXT will provide new insights for flare studies.

Program listing for Friday