Coronal X-ray sources

fl228.alexander05
Posted:  04-Feb-96
Updated: 20-Sep-96
Events specified: N/A

D. Alexander, J.I. Khan, T. Metcalf, H. Hudson

Flaring events which display hard X-ray sources in the corona have proved to be among the most exciting phenomena discovered by Yohkoh. There has been much controversy over these events and many interpretations of the data and development of models to explain the data. We plan to utilise the pixon image reconstruction technique developed for the Yohkoh Hard X-ray Telescope (HXT) data by Tom Metcalf, to investigate the properties of coronal hard X-ray sources. In particular, we have been studying the time development of the coronal sources in relation to that of the co-temporary footpoint emission. Understanding these phenomena can tell us more about what powers a solar flare, what governs the particle acceleration and how the energy is distributed.

Progress her has been made in the study of the 13-Jan-92 (Masuda) event in that we have determined distinct differences in the behaviour of the individual hard X-ray sources as determined by other colleagues using the MEM reconstruction tool. Initial analysis has involved the testing of the pixon code both for its dependence on instrument parameters and in comparison to the MEM approach.

Special note to your proposal from SXT DUC: This proposal has an overlap with the following proposals. Although there is no restriction on you proposal, DUC would appreciate it if you closely communicate with the authors of the following project:

fl151: Vertical Structure of Thermal/Nonthermal Hard X-ray Sources in Solar Flares (Masuda)

Update 20-Sep-96

This work is curently being written up for publication. A poster paper discussing the comparison of pixon reconstructions with those of MEM was presented at the Yohkoh meeting in Bath, England. A workshop is being organised for early January to elicit thoughts on the development of HXT analysis software and to make significant headway into the image reconstruction.

Our analysis of the hard X-ray images has shown a "pre-cursor" looptop emission in the HXT M1 channel prior to the main impulsive phase of the flare. This is being studied in terms of various models of hard X-ray bremmstrahlung production.