Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010a%26a...521a..56s&link_type=abstract
Astronomy and Astrophysics, Volume 521, id.A56
Astronomy and Astrophysics
Astrophysics
6
Sun: Activity, Sun: Coronal Mass Ejections (Cmes), Magnetic Fields
Scientific paper
Context. Coronal mass ejections (CMEs) are very energetic events (~ 1032 erg) initiated in the solar atmosphere, resulting in the expulsion of magnetized plasma clouds that propagate into interplanetary space. It has been proposed that CMEs can play an important role in shedding magnetic helicity, avoiding its endless accumulation in the corona. Aims: The aim of this work is to investigate the behavior of magnetic helicity accumulation in sites where the initiation of CMEs occurred to determine whether and how changes in magnetic helicity accumulation are temporally correlated with CME occurrence. Methods: We used MDI/SOHO line-of-sight magnetograms to calculate magnetic flux evolution and magnetic helicity injection in 10 active regions that gave rise to halo CMEs observed during the period 2000 February to 2003 June. Results: The magnetic helicity injection does not have a unique trend in the events analyzed: in 40% of the cases it shows a large sudden and abrupt change that is temporally correlated with a CME occurrence, while in the other cases it shows a steady monotonic trend, with a slight change in magnetic helicity at CME occurrence. Conclusions: The results obtained from the sample of events that we have analyzed indicate that major changes in magnetic helicity flux are observed in active regions characterized by emergence of new magnetic flux and/or generating halo CMEs associated with X-class flares or filament eruptions. In some of the analyzed cases the changes in magnetic helicity flux follow the CME events and can be attributed to a process of restoring a torque balance between the subphotospheric and the coronal domain of the flux tubes.
Appendix is only available in electronic form at http://www.aanda.org
Guglielmino Salvatore L.
Hood Alan William
Mackay Dr.
Romano Pado
Smyrli Aimilia
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