Twist Propagation in Hα Surges
Abstract
Hα surges are straight or slightly curved ejections that reach heights of 200 Mm and typically last 10-30 minutes. The surge material either fades or returns into the chromosphere along the trajectory of accent. It has been proposed that reconnection of magnetic fields accounts for Hα surges [2,3]. Previous observations demonstrated Hα surges are seen in the early stages of flux emergence [1]. We have studied 11 active regions, selected for surge activity, with observations from the Mees Solar Observatory's CCD Imaging Spectrograph and Haleakala Stokes Polarimeter (HSP). The spectroheliograms were made into movies showing Hα line center and the corresponding Doppler velocities from the shift in the \ha\ absorption line center. The direction of stored twist in the magnetic field is determined from the force-free field parameter, α , where ∇ x B =\ α B, computed from HSP vector magnetograms. The magnetogram and velocity data were coregistered and the relationship between the surge spin and the stored twist in the magnetic field was recorded. Statistical analysis of the data found with a 99% confidence level that the direction of observed spin of the surge is consistent with the relaxation of the stored twist in the magnetic field at the point where the surge originated. [1] Kurowaka, H. & Kawai, G 1993, The Magnetic and Velocity Fields of Solar Active Regions, ed. H. Zirin, G. Ai, & H. Wang, ASP Conf. Ser., 46, 507. [2] Roy, J.-R. 1973, Solar Physics, 28, 95. [3] Rust, D. M. 1968, Structure and Development of Solar Active Regions, ed. K. O. Kiepenheuer, IAU Symposium 35, p 77.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2001
- Bibcode:
- 2001AGUSM..SP51B08J
- Keywords:
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- 7500 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7524 Magnetic fields