ar073.bastian03 Posted: 18-Oct-94 Updated: 29-Jun-95 Events specified: AR 7124
Collaborators: T.S. Bastian, A. Vourlidas, M. Aschwanden, N. Nitta
Motivation: As part of an extended observing campaign during the first two weeks of April, 1992, the VLA and Yohkoh observed the rapid growth and decay of a so-called "anemone" active region on 3-4 April (AR 7124). In general, discrete coronal loop systems are rarely resolved at radio wavelengths due to optical depth effects and scattering. In the case of AR 7124, however, several discrete loops are well-resolved by both the VLA and the SXT due to its "anemone"-like morpholgy. The objective of the present study is two-fold: i) to compare physical parameters derived from both radio and SXR techniques for discrete loops; ii) to study the temporal evolution of physical parameters of an "anemone" active region over the two days of its lifetime.
Required Data/Progress: We will use the PFI frames from the SXT to determine the T and EM of AR7124 as a function of time on 4 April 1992. These quantities will be compared with those deduced from the multiband multiband VLA radio observations. The radio data analysis is complete. The SXR analysis will be completed by the end of 1994.
Update 29-Jun-95
Attached is the abstract of the paper concerning "Joint Radio and SXR Imaging of and 'Anemone' Active Region". The paper has been submitted to Solar Physics and has been refereed - it is currently being revised. The project may be closed.
Joint Radio and Soft X-ray Imaging of an ``Anemone'' Active Region
A. Vourlidas, T. S. Bastian, N. Nitta, M. J. Aschwanden
The Very Large Array and the Soft X-ray Telescope aboard the Yohkoh satellite observed the rapid growth and decay of a so-called ``anemone'' active region on 3-6 April (AR 7124). In general, discrete coronal loop systems are rarely resolved at radio wavelengths due to optical depth effects and scattering. Due to its unusual anemone-like morphology, however, several discrete loops or loop systems are resolved by both the VLA and the SXT in AR7124.
We find that the microwave emission at 4.7 and 8.4 GHz is the result of gyroresonance emission from a hot, rarified plasma. The decimetric source is complex -- 1.5 GHz emission from the leading part of AR 7124 is due to free-free emission, while that in the trailing part of the active region is dominated by gyroresonance emission.