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Magnetic energy dissipation and its Correlation with Hard X-ray Emission in the 2002 July 23 Solar Flare View all project descriptions by submitter

Valentina Zharkova Submitted: 26-Oct-2003 09:14

We analyze the SOHO/MDI high-cadence magnetic field variations occuring prior and during the 2002 July 23 flare $2B/X4.8$ and their association with the hard X-ray and $H_{alpha}$ emission observed with RHESSI and BBSO. The X-ray emission in the 12-25 KeV band started at 00:25:00 UT, reached the maximum at 00:28:00 UT and 1 minute later was followed by emission in the higher bands. The line-of-sight (LOS) magnetic field variations associated with the flare 23 July 2002 occurred in the bipolar area around an apparant neutral magnetic line (ANL)located with the automated dual distance technique. The variations of a total magnetic flux and Poynting flux from a flaring area were calculated using the ANL measurements with 1 minute cadence before and after the first X-ray burst. At 00:21:00 UT a total magnetic flux measured from the whole flaring area revealed a brief decrease about a few percent of $6cdot10^{20}$ Mx that lasted until 00:23:00 UT when the magnetic flux started a steady increase up $8.4cdot10^{20}$ Mx lasting until 00:35:00 UT when the magnetic field returned to noise fluctuations about this new magnitude. The first increase of hard X-ray emission ( a pre-cursor in the far-east hard X-ray footpoint) as well as the first brightenning in the $H_{alpha}$ ribbon on the north-west from the neutral magnetic line started at 00:22:00 UT that coincides with the first magnetic field irreversible changes while the major increase in hard X-ray emission in the 12-25 KeV band occurred at 00:28:00 UT that was in the middle of the registered magnetic field changes. In addition, there were reversible magnetic field changes of a 'transient' type occurring in the other two hard X-ray footpoints (north-east and west) and simultaneously in the $H_{alpha}$ ribbons appearing on the both sides from the neutral line where magnetic field returned to a pre-flare level after the flare offset. The irreversible magnetic field growth was located in the forth hard X-ray footpoint located on the south-east from ANL with the strongest negative LOS magnetic field, it started 2 minutes prior the flare, increased by 110 G and stayed at this level after the flare offset. A correlation coefficient of the irreversible magnetic field variations with the lower energy hard X-ray emission increased from zero at the start to 0.5 at 00:28:00 UT in the middle of the changes. In the higher energy band of 300 KeV- 1 MeV the correlation coefficient was about 0.4 at the beginning of irreversibe magnetic changes and reached 0.6 just after the maximum of hard X-rays in this band. The rate of irreversible magnetic changes, possibly caused by magnetic reconnection during the flare, was about $1cdot10^{18}$ Mx/s and the Poynting flux was about $2cdot 10^{12}$ $erg/cm^2/s$ that results in the magnetic energy released during this flare of $sim 1cdot 10^{32}$ erg.

Participants: S.I.Zharkov, S.S.Ipson and A.K.Benkhalil

Project Status: J.Geophys.Res, v.110 Go to main RHESSI project descriptions page  Using RHESSI to constrain the causes of coronal waves and shocks  Edit Entry  Submitter's Homepage

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