fl209.gary01 Posted: 17-Jul-95 Updated: 24-Feb-96 Events specified: Flare of 11-Feb-93 18:29 UT
D. E. Gary, H. Wang, N. Nitta and T. Kosugi
A solar flare that occurred on 1993 February 11 displays a prominent, long-lasting plateau in both microwave flux observed with the Owens Valley Radio Observatory (OVRO) Solar Array and in soft X-ray flux observed with the GOES spacecraft. Yohkoh SXT data taken at the same time show a large, bright flare-activated loop that develops soon after the flare and persists for at least one hour. An examination of the OVRO microwave flux spectrum shows a remarkably flat shape above 2 GHz, suggesting classic, optically thin thermal bremsstrahlung emission. We investigate whether the bright loop seen in the Yohkoh data can account for the GOES flux, and whether both soft X-ray observations are consistent with the radio spectrum.
We find at the time of peak development of the loop that the best single-temperature fit needed to explain the flux density of the optically thin (flat) part of the radio spectrum is different from that determined from GOES. We use the loop shape, size, and position determined from the Yohkoh SXT data to convert the radio flux spectrum into a brightness temperature spectrum. In this form, it appears that the discrepancy with GOES temperature and emission measure could be explained in terms of a multi-thermal coronal model.
We now wish to investigate the formation and longevity of the loop, and compare the radio and soft X-ray parameters that are needed to account for the loop at all times during its evolution. We expect that the temperature and emission measure of the loop will change with time in a way that should shed light on heat input and cooling times. The contribution of nonthermal particles in heating the loop can be investigated in the early stages of the loop formation, since the radio spectrum at this early time shows departures from a strictly thermal shape.
Updated 24-Feb-96
The following TBB item:
Microwave and Soft X-ray Observations of Thermal Bremsstrahlung from a Flare-Activated Loop
by D. E. Gary, H. Wang, N. Nitta and T. Kosugi
has been submitted to Ap. J. and has been accepted. It was carefully reviewed by the two Yohkoh team co-authors, N. Nitta and T. Kosugi. It can be considered a closed research topic now.