The Magnetic Free Energy and a CME in Active Region 8299 |
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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
Projects:
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Publication Status: ApJ, Submitted, July 2001
Last Modified: 2001-07-17 10:43
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