Characteristics of magnetic helicity flux in the solar active region photosphere
ISEE, Nagoya University
Main category
Natural Sciences (Astrophysics and Astrononmy)
We investigated statistical characteristics of magnetic helicity injected per unit time through the active region photosphere using vector magnetic field data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The photospheric helicity injection rate of a given active region was calculated from the formula of the gauge-invariant relative helicity flux derived by Berger and Field (1984), applying the optical flow technique Differential Affine Velocity Estimator for Vector Magnetogram (DAVE4VM) to co-registered pairs of vector magnetograms sampled 12 minutes apart. We determined helicity injection rates for a total of 30,628 SHARP vector magnetogram pairs sampling 866 unique active regions from 2012 September to 2016 December. Using this large data set, we studied long-term, large-scale characteristics of helicity injection rates in the active region photosphere. We will present how helicity injection rates are distributed with respect to Heliographic latitude, Carrington longitude, solar cycle epoch and Hale magnetic class. It will be also discussed how helicity injection rate is related to other magnetic parameters and flare productivity of active regions.
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