Issue |
A&A
Volume 461, Number 2, January II 2007
|
|
---|---|---|
Page(s) | 697 - 706 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20065751 | |
Published online | 16 October 2006 |
Reconnection and energy release rates in a two-ribbon flare
1
Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
2
Hvar Observatory, Faculty of Geodesy, Kačićeva 26, 1000 Zagreb, Croatia
Received:
2
June
2006
Accepted:
13
September
2006
Aims.The aim of this study was to derive the local reconnection rate (coronal electric field) and the global reconnection rate (magnetic flux change rate), as well as the energy release rate (Poynting flux), in a two-ribbon flare from chromospheric/photospheric observations. Furthermore, we tested whether equal shares of positive and negative magnetic flux are involved in the flare process.
Methods.A well-observed GOES M3.9 two-ribbon flare was analyzed. The required observables
(ribbon expansion velocity, newly brightened area, and magnetic field strength at
the ribbon front) were extracted from the TRACE 1600 Å and Kanzelhöhe
Hα image time series, and a SOHO MDI magnetogram. Furthermore, the ratio of
the converted positive vs. negative magnetic flux was determined. Both RHESSI hard
X-ray keV full-disk time profiles and subregion time profiles derived from
a time series of RHESSI images in the same energy range were used as independent,
observable proxies for the energy release rate. The RHESSI images were also used
to localize the sites where the bulk of the energy was deposited by fast
electrons.
Results.We found good temporal correlations between the derived time profiles (local
and global reconnection rate, Poynting flux) and observed HXR flux. The local
reconnection-rate peak values ranged from to
, whereas the positive and the negative magnetic flux
covered by the flare emission were equal within
%.
Conclusions.The results indicate that the local reconnection rate, the global reconnection rate, and the energy release rate in a simple two-ribbon flare can be derived from chromospheric/photospheric observations. Furthermore, it was confirmed that equal shares of positive and negative magnetic flux participated in the reconnection process.
Key words: Sun: flares – Sun: magnetic fields – Sun: chromosphere – Sun: corona
© ESO, 2006
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