Confirmation of the "Main Sequence” of Explosive Active Regions

Details Confirmation of the "Main Sequence” of Explosive Active Regions Confirmation of the "Main Sequence” of Explosive Active Regions

May 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21640612f&link_type=abstract

American Astronomical Society, AAS Meeting #216, #406.12; Bulletin of the American Astronomical Society, Vol. 41, p.881

Astronomy and Astrophysics

Astronomy

Scientific paper

We examine the location and distribution of the production of coronal mass ejections (CMEs) and major flares by mature sunspot active regions in the phase space of two whole-active-region magnetic quantities measured from SOHO/MDI magnetograms of 420 active regions during their passage within 0.5 RSun of disk center. This study is a ten-fold expansion of our recent exploratory study (Falconer et al 2009, ApJ, 700, L166). The two measured magnetic quantities are LΦ, a measure of an active region's total magnetic flux, and LWLSG, a proxy of the total free energy in the active region's magnetic field above the photosphere. For each active region we also have (1) the times of CMEs, X flares, and M flares produced during disk passage, and (2) at the time of each magnetogram, a measure of the active region's power output in major flares, the 48-hour average power output in 1-8 Å radiation from its X and M flares. In agreement with our exploratory study, we again find (1) CME/flare-productive active regions are concentrated in a "main sequence” along a straight line in (Log LΦ, Log LWLSG) space, (2) this line is close below an upper edge of maximum attainable free magnetic energy, and (3) the average flare-power measure increases steeply across this line as the free-energy-limit edge is approached. As before, this third result suggests that the main sequence of explosive active regions results from equilibrium between the input of free energy by contortion of the field via convection in and below the photosphere and loss of free energy via CMEs, flares, and coronal heating, an equilibrium between energy gain and energy loss that is analogous to that for the main sequence of hydrogen-burning stars in Mass-Luminosity space.
NASA's LWS/TR&T Program, AFOSR's MURI Program, and NASA's TEI Program funded this work.

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