Astronomy and Astrophysics – Astronomy
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009spd....40.1909w&link_type=abstract
American Astronomical Society, SPD meeting #40, #19.09; Bulletin of the American Astronomical Society, Vol. 41, p.848
Astronomy and Astrophysics
Astronomy
Scientific paper
We estimated photospheric velocities by separately applying the Fourier Local Correlation Tracking (FLCT) and Differential Affine Velocity Estimator (DAVE) methods to 2708 co-registered pairs of SOHO/MDI magnetograms, with nominal 96-minute cadence, from 46 active regions (ARs) from 1996-1998 over the time interval κ45 when each AR was within 45° of disk center. For each magnetogram pair, we computed the average estimated radial magnetic field, BR and each tracking method produced an independently estimated flow field, u. We then quantitatively characterized these magnetic and flow fields by computing several extrinsic and intrinsic properties of each; extrinsic properties scale with AR size, while intrinsic properties do not depend directly on AR size. Intrinsic flow properties included moments of speeds, horizontal divergences, and radial curls; extrinsic flow properties included included sums of these properties, and a crude proxy for the ideal Poynting flux, ∑ |u| BR2. Several quantities derived from BR were also computed, including: total unsigned flux, Φ a measure of the amount of unsigned flux near strong-field polarity inversion lines (SPILs), R and ∑ BR2. Next, using correlation and discriminant analysis, we investigated the associations between derived properties and average flare flux determined from the GOES flare catalog, when averaged over both κ45 and shorter time windows, of 6 and 24 hours. Our AR sample included both flaring and flare-quiet ARs; the latter did not flare above GOES C1.0 level during κ45. Among magnetic properties, we found R to be most strongly associated with flare flux. Among extrinsic flow properties, the proxy Poynting flux, ∑ |u| BR2, was most strongly associated with flux, at a level comparable to that of R. All intrinsic flow properties studied were more poorly associated with flare flux than these magnetic properties.
Fisher George H.
Li Yadong
Schuck Peter W.
Welsch Brian
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