The "Main Sequence” of Explosive Solar Active Regions: Discovery and Interpretation

Details The "Main Sequence” of Explosive Solar Active Regions: Discovery and Interpretation The "Main Sequence” of Explosive Solar Active Regions: Discovery and Interpretation

May 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009spd....40.1925f&link_type=abstract

American Astronomical Society, SPD meeting #40, #19.25; Bulletin of the American Astronomical Society, Vol. 41, p.851

Astronomy and Astrophysics

Astronomy

Scientific paper

We examine the location and distribution of the production of coronal mass ejections (CMEs) and major flares by sunspot active regions in the phase space of two whole-active-region magnetic quantities measured from 1865 SOHO/MDI magnetograms. These magnetograms track the evolution of 44 full-grown active regions across the central disk of radius 0.5 RSun. The two quantities are LWLSG, a gauge of the total free energy in an active region's magnetic field above the photosphere, and LΦ, a measure of the active region's total magnetic flux. 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. From these data, we find that (1) CME/flare-productive active regions are concentrated in a straight-line "main sequence” in (Log LWLSG, Log LΦ) space, (2) this line is close behind a front of maximum attainable magnetic twist, and (3) the average flare-power measure increases sharply across this line as the leading front is approached. These results suggest 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 was funded by NASA's LWS TR&T Program, NSF's SHINE Program, AFOSR's MURI Program, and NASA's Technical Excellence Initiative Program.

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