HR: 0800h
AN: SH11A-0248    [Abstracts]
TI: Measuring Braiding and Spin Helicity Fluxes in Active Regions
AU: * Belur, R
EM: ravindra@solar.physics.montana.edu
AF: Montana State University, Department of Physics, Bozema, MT 59717 United States
AU: Longcope, D W
EM: dana@solar.physics.montana.edu
AF: Montana State University, Department of Physics, Bozema, MT 59717 United States
AU: Barnes, G
EM: barnes@cora.nwra.com
AF: Colorado Research Assoc. Div. NorthWest Research Assoc., 3380 Mithcell Lane, Boulder, CO 80301 United States
AB: Magnetic helicity has become a valuable theoretical tool for understanding the dynamics of the solar corona. The free energy stored in the coronal magnetic field can be estimated based on its helicity content. Furthermore, rapid release of stored energy must be accomplished while preserving the total magnetic helicity. Recently long time-sequences of magnetograms have been used to measure the flux of helicity into active regions. We demonstrate how this helicity flux can be usefully decomposed into a sum of spin helicity terms and an overall mutual helicity term. Each magnetogram is partitioned into a set of unipolar regions. These must persist through the sequence and track the photospheric flow. The spin helicity of a given region quantifies the effects of motions internal to that region, while braiding helicity is injected by the motions of whole regions about one another. Since the terms themselves can be of different signs it is possible to re-distribute the coronal helicity by reconnection without changing the overall helicity content. This decomposition is demonstrated on active region observations.
DE: 7524 Magnetic fields
DE: 7529 Photosphere
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005