Electric currents in unipolar active regions with different magnetic flux decay rates in sunspots
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Abstract
Using the magnetographic data of the Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO), we calculated parameters of the magnetic field and electric currents for unipolar active regions (ARs) with low (≤ 2.1 × 1019 Mx h−1; in total, 11 ARs were analyzed) and high (≥ 7.0 × 1019 Mx h−1, 5 ARs were analyzed) magnetic flux decay rates in sunspots. We obtained the following results: 1) the stronger the local (small-scale) electric currents in the vicinity of a unipolar sunspot, the faster its decaying; 2) the distributed (global, large-scale) electric current around the rapidly decaying sunspots is practically zero. There cannot be expected a stabilizing effect on the decay of a sunspot; 3) in four cases of slowly decaying sunspots, a nonzero distributed electric current of up to 5.0 × 1012 A was detected. Perhaps such electric current can have a stabilizing effect on the decay of a sunspot.
Thus, our findings indicate that strong electric currents of small scales have a rather destructive effect on a sunspot, and the presence of large-scale currents can stabilize it. However, this mechanism seems not to be the only one and dominant in the processes of stabilization of unipolar sunspots.
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