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A. Nindos (Section of Astrogeophysics, Physics Dept., University of Ioannina, Greece), M.D. Andrews (Computational Physics Inc., NRL)
In a recent study Andrews (2003) found that approximately 40% of the GOES soft X-ray M-class flares observed during the years 1996-1999 are not associated with CMEs. In this paper, we investigate the role of magnetic helicity in the association of big flares and CMEs. We compute the coronal relative magnetic helicity of all active regions which were located within ±50 degr from the central meridian and produced M-class flares during the years 1996-1999. The computations use SOHO/MDI magnetograms taken close to the initiation of each event as boundary conditions for "constant alpha" linear force-free field magnetic extrapolations. The extrapolated field lines are fitted with the corresponding active region's coronal loops observed with EIT at 195 A. Then the value of alpha giving the best fit between the models and the coronal observations is adopted for the computation of the coronal magnetic helicity. Within the uncertainties involved in our computations, we find that the coronal magnetic helicity of about 65-70% of the active regions which gave M-class flares without CMEs is smaller than the coronal magnetic helicity of all active regions which gave M-class flares associated with CMEs.
The author(s) of this abstract have provided an email address for comments about the abstract: anindos@cc.uoi.gr
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.