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The Magnetic Free Energy and a CME in Active Region 8299  

Thomas R. Metcalf   Submitted: 2001-07-17 10:43

We calculate the magnetic free energy as a function of time for NOAA active region 8299 on 1998 August 11 using vector magnetic field measurements in the NaI 5896A spectral line observed with the Imaging Vector Magnetograph at Mees Solar Observatory. The free energy in this active region is significant with a magnitude of about 1033 ergs, though the active region was not flare productive. This amount of free energy is more than enough to explain the enhanced heating of the active region corona. The free energy dipped to a value consistent with zero for one hour during the observation. Yohkoh/SXT images reveal that, around the time of this dip in the free energy, the coronal structure of AR 8299 and the nearby AR 8297 changed significantly. SXT observed the brightening of a cusp connecting AR 8299 and AR 8297 and observed coronal dimming in both active regions, suggesting that a gradual CME was launched as the magnetic energy dipped. Further, the magnetic connection between AR 8299 and AR 8297 was temporarily severed during the energy dip and the magnetic field took on a more open configuration afterwards. Unfortunately, LASCO data were not available to confirm the existence of a halo CME. However, the circumstantial evidence points to the magnetic free energy as the energy source for the postulated event.

Authors: Thomas R. Metcalf, Donald L. Mickey, Barry J. LaBonte, and Leigh Ann Ryder

Publication Status: ApJ, Submitted, July 2001
Last Modified: 2001-07-17 10:43
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