Abstract
We derive a time series of two-dimensional velocity fields for a flare region on 1992 December 16, based on the asymmetries of the Hα line. The Hα spectra were obtained by an imaging spectrograph at the Solar Tower Telescope of Nanjing University. Four sites with evident chromospheric downflows are found to appear and decay consecutively in the studied region. The value of maximum velocities is 30–40 km s−1 and the lifetime of downflows is 2–3 min at these sites. It is also shown that the asymmetries only exist at the line wing, while the line center has nearly no shifts for this flare. Finally, we make a discussion on the characteristics of the velocity distribution and its correlations with the intensity distribution, as well as with the hard X-ray emission.
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Ding, M.D., Fang, C. & Huang, Y.R. Analysis of 2-d flare spectra: Velocity fields derived from Hα line asymmetries. Sol Phys 158, 81–93 (1995). https://doi.org/10.1007/BF00680836
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DOI: https://doi.org/10.1007/BF00680836