Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh43b1817z&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SH43B-1817
Astronomy and Astrophysics
Astrophysics
[7513] Solar Physics, Astrophysics, And Astronomy / Coronal Mass Ejections, [7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7524] Solar Physics, Astrophysics, And Astronomy / Magnetic Fields
Scientific paper
Coronal Mass Ejections (CMEs) are very energetic events 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. We therefore investigated the behavior of magnetic helicity accumulation in sites where the initiation of CMEs occurred, in order to determine whether and how changes in magnetic helicity accumulation are temporally correlated with CME occurrence. After identifying the active regions (AR) where the CMEs were initiated by means of a double cross-check based on the flaring-eruptive activity and the use of SOHO/EIT difference images, we use MDI magnetograms to calculate magnetic flux evolution magnetic, helicity injection rate and magnetic helicity injection in 10 active regions that gave rise to 12 halo CMEs observed during the period February 2000 - June 2003. No unique behavior in magnetic helicity injection accompanying halo CME occurrence is found. In fact, in some cases there is an abrupt change in helicity injection timely correlated with the CME event, while in some others no significant variation is recorded. However, our analysis show that the most significant changes in magnetic flux and magnetic helicity injection are associated with impulsive CMEs rather than gradual CMEs. Moreover, the most significant changes in magnetic helicity are observed when X-class flares or eruptive filaments occur, while the occurrence of flares of class C or M seems not to affect significantly the magnetic helicity accumulation. Finally, this study shows that magnetic helicity accumulation in our sample of ARs generating halo CMEs has sudden and abrupt changes only in 40 % of the cases examined and that a correlation between the helicity injection changes and the nature (gradual or impulsive) of the CMEs seems to exist.
Poedts Stefaan
Romano Pado
Smyrli Aimilia
Zuccarello F. P.
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