Confirmation of the 'Main Sequence' of Explosive Active Regions
Abstract
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 18,800 SOHO/MDI magnetograms. These magnetograms track the evolution of 420 mature active regions across the central disk of radius 0.5 RSun. A mature active region is one that has completed its rapid-emergence birth phase. The present study is an expansion of a previous initial study (Falconer, Moore, Gary, & Adams 2009, ApJ 700 L166), for which the sample was 1,865 magnetograms from 44 mature active regions. The two whole-active-region magnetic quantities are L⊙, a measure of the active region's total magnetic flux, and LWLSG, a proxy of the total free energy in an active region's magnetic field above the photosphere. We compiled each active region's production of CMEs, X flares, and M flares during its rotation across the disk. In addition, at the time of each magnetogram, we evaluated from the NOAA Catalog of Active Region Flares a flare-power measure, the active region's 48-hour average power output in 1-8 Å radiation from X and M flares. In agreement with our previous study, from the present expanded sample we again find that (1) CME/flare-productive active regions are concentrated in a 'main sequence' along a straight line in (Log L⊙, 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 sharply across this line as the free-energy-limit front is approached. As before, this third result suggests that the main sequence of explosive active regions is the consequence of equilibrium between 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 loss that is analogous to that of the main sequence of hydrogen-burning stars in Mass-Luminosity space.
This work is funded by the NSF SHINE Program, by the NASA LWS TR&T Program, by the AFOSR MURI Program, and by the NASA Technical Excellence Initiative.- Publication:
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Solar Heliospheric and INterplanetary Environment (SHINE 2010)
- Pub Date:
- July 2010
- Bibcode:
- 2010shin.confE.106F