Origin of the Sheared Magnetic Fields that Erupt in
Flares and Coronal Mass Ejections
Ron Moore and Alphonse Sterling
From a search of the Yohkoh/SXT whole-Sun movie in the years 2000 and 2001,
we found 37 flare-arcade events for which there were full-disk magnetograms
from SOHO/MDI, coronagraph movies from SOHO/LASCO, and full-disk chromospheric
images from SOHO/EIT and/or from ground-based observatories. Each of these
events was apparently produced by the ejective eruption of sheared core
magnetic field (as a flux rope) from along the neutral line inside a mature
bipolar magnetic arcade. Two thirds (25) of these bipoles had the normal
leading-trailing magnetic polarity arrangement of active regions in the
hemisphere of the bipole, but the other third (12) had reversed polarity,
their leading flux being the trailing-polarity remnant of one or more old
active regions and their trailing flux being the leading-polarity remnant of
one or more other old active regions. From these observations, we conclude:
(1) The sheared core field in a reversed-polarity bipole must be formed by
processes in and above the photosphere, not by the emergence of a flux rope
bodily from below the photosphere. (2) The sheared core fields in the
normal-polarity bipoles were essentially the same as those in the
reversed-polarity bipoles. (3) Hence, the sheared core fields in
normal-polarity mature bipoles are likely formed mainly by the same
processes as in reversed-polarity bipoles. (4) A prime objective of
Solar-B should be to discover and elucidate these processes.
Correspondence
Ron Moore (ron.moore@nasa.gov), NASA/MSFC/NSSTC
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