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Magnetic Energy and Helicity in Two Emerging Active Regions in the Sun View all abstracts by submitter

Yang Liu   Submitted: 2012-10-31 11:33

The magnetic energy and relative magnetic helicity in two solar active regions AR 11072 and AR 11158 during their emergence are studied. They are computed by integrating over time, the energy- and relative helicity-fluxes across the photosphere. The fluxes consist of two components: one from photospheric tangential flows that shear and braid field lines (shear-term); the other from normal flows that advect magnetic flux into the corona (emergence-term). For these active regions (1) relative magnetic helicity in the active-region corona is mainly contributed by the shear-term; (2) helicity fluxes from emergence-term and shear-term have the same sign; (3) magnetic energy in the corona (including both potential energy and free energy) is mainly contributed by emergence-term; and (4) energy fluxes from emergence-term and shear-term evolved consistently in phase during the entire flux emergence course. We also examine the apparent tangential velocity derived by tracking field-line footpoints using a simple tracking method. It is found that this velocity is more consistent with tangential plasma velocity than with the flux transport velocity, which agrees with the conclusion in Schuck (2008).

Authors: Yang Liu, Peter W. Schuck
Projects: SDO-HMI

Publication Status: ApJ accepted
Last Modified: 2012-10-31 12:13
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