Co-Registered High-Time-Resolution Images and Spectra of the 1991 January 11 18:25 UT flare.
Abstract
The 1B/M1.0 flare of 1991 January 11 18:25 UT was simultaneously observed in Hα by two complementary instruments. Spectra and spectroheliograms were obtained from the Mees Solar Observatory CCD Imaging Spectrograph (MCCD) at the University of Hawai`i, while line-center and blue-wing (-1.3 Angstroms) images were made at 0.1 s time resolution by the NASA/GSFC High-Speed Hα Camera (HSHC) at the University of Colorado at Boulder. >From the MCCD data we identify sites showing the spectral signatures of nonthermal electron precipitation, high coronal pressure, or mass motions. We detect strong precipitation, and find reasonable agreement between the observed line profiles and theoretical precipitation spectra. We consider the possibility that the observed spectra actually arise from a projection effect and we indicate limitations of the one-dimensional theoretical models. We also observe redshifted emission which may be the signature of a chromospheric condensation, and we compare the downflow velocity with that predicted by the numerical model of Fisher. The slowing-down time of the observed downflow is about four times longer than in the model, perhaps because of the superposition of several unresolved condensations.
- Publication:
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American Astronomical Society Meeting Abstracts #180
- Pub Date:
- May 1992
- Bibcode:
- 1992AAS...180.4506D