ar005.metcalf02 Posted: 26-Jan-92 Updated: 05-Aug-92, 06-Apr-93, 06-Nov-93 Events specified: NOAA AR 6952
Collaboration: T. Metcalf, R. Canfield, J.-P. Wuelser, K. D. Leka, H. Hudson, D. Mickey, Y. Uchida, S. Tsuneta
Question: 1) What relation, if any, exists between SXR emission and currents in active regions? 2) How do the SXR's and current systems evolve in time? Do they evolve independently, or are the evolutions interdependent?
Motivation: This project is designed to study the morphological relationship between active region SXR emission observed with SXT and vertical electric currents in the photosphere and chromosphere computed from vector magnetograms obtained at Mees Observatory. The goal is to observe an active region over the course of several days to get a handle on the evolution of the region.
Required Observations/Analysis Techniques: 1) Observe AR magnetic field and vertical current evolution (Mees) 2) Observe AR SXR evolution (SXT). The data to be used are:
Update 06-Nov-93
This project has been completed and a paper submitted to Ap.J.
Summary:
While some spatial and temporal coincidence between active region electric current systems and bright SXR structures is observed in SXT images co-aligned with vector magnetograms, there is no compelling link between the currents and the SXR structures. Most likely, photospheric currents and bright SXR structures simply tend to occur in the most active areas of the active region and hence sometimes appear together. We do not find evidence which directly links these electric currents observed in the photosphere to the heating of the coronal plasma indicated by the SXR brightness and temperature. Thus, since we know that sufficiently filamented currents can cause significant heating, the currents observed in AR6952 can not be highly filamented in the corona. Further, if fine scale currents do heat the corona and cause the bright SXR emission, they must not be organized into large scale patterns in the photosphere.
Update 06-Apr-93
This study is essentially complete and work on the paper is continuing.
We examined the spatial and temporal relationship between coronal structures observed with the Soft X- ray telescope (SXT) on board the YOHKOH spacecraft and the vertical electric currents derived from vector magnetograms obtained at the Mees Solar Observatory, Haleakala, Hawaii. In the paper we focus on a single active region: AR 6952 observed in December, 1991. We compare the vertical electric current to the non-flaring X-ray images and find no compelling, direct spatial and temporal correlation between the sites of vertical current and the sites of bright X-rays.
Update 05-Aug-92
This study is proceeding with data from AR6952 (December 1991).