An Observational Technique for Quantifying the Rate of Magnetic Reconnection

D.W. Longcope, D.E. McKenzie, J. Cirtain and J. Scott

Magnetic reconnection is evidently at work restructuring the solar corona and possibly even heating its plasma. To better quantify its contribution to heating it is essential to quantify the rate of magnetic reconnection in some context. Defining reconnection narrowly and topologically, as a change in the footpoints of a coronal field line, makes its quantification a problem of counting coronal field lines connecting a pair of opposing photospheric regions. We have conducted a prototype measurement of this kind involving one bipolar active region (AR9574) emerging in the immediate vicinity of an existing one (AR9570) over 2001 August 10-11. Shortly after emergence begins TRACE 171A images show coronal loops interconnecting the two regions; these are necessarily the result of coronal reconnection. We use 41 hours of high-cadence TRACE data to quantify the rate interconnecting loops appear. Using a magnetic model we conclude the reconnection rate averaged 35 megavolts over the entire period. Most of the reconnection occurs in a brief interval (3-6 hrs) beginning 24 hours after emergence onset. During this interval the reconnection rate was as high as 260 MV. The reconnection episode appears to coincide with a period of heating observed in soft X-ray images of Yohkoh SXT.

Correspondence

Dana W. Longcope (dana@mithra.physics.montana.edu)

presentation

oral