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Correlating Transition Region Explosive Events with Extreme-Ultraviolet Brightenings

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Amy R. Winebarger1,2, Adria C. Updike3 and Katharine K. Reeves1

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Frequent small-scale reconnection events have been proposed as a possible mechanism to heat the solar corona. It has not yet been demonstrated, however, that the smallest reconnection events can heat the plasma to coronal temperatures. In this Letter, we use explosive events in the spectral line C IV λ1548 observed by the Solar Ultraviolet Measurement of Emitted Radiation instrument flown aboard the Solar and Heliospheric Observatory to locate areas of reconnection in Active Region 8536 on 1999 May 13. We then examine coaligned Transition Region and Coronal Explorer (TRACE) 171 Å images for a response to the reconnection. We find that short-term (<5 minute) fluctuations are on average 2.2 times larger in regions of reconnection than in comparison (nonevent) regions. These fluctuations are statistically significant (3 σ above the mean intensity fluctuation in the nonevent regions) in 35% of the reconnection regions. We find two possible explanations for the 171 Å intensity fluctuations: (1) the explosive event plasma could be heated to 1 MK, or (2) the emission measure of the O VI λ172 line could increase because of a surge of transition region material that would, in turn, increase the 171 Å intensity. The latter explanation would imply that not all transient brightenings in the TRACE data are associated with plasma at coronal temperatures.


Subject headings

Sun: activity; Sun: corona


Dates

Issue 2 (2002 May 10)

Received 2001 December 13, accepted for publication 2002 April 9

Published 2002 April 15



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