MAGNETIC HELICITY EXCHANGE BETWEEN NEIGHBORING ACTIVE REGIONS

Abstract

Addressing the long-lasting problem of the magnetic helicity distribution in the solar corona, a proof for magnetic helicity exchange between two neighboring emerging active regions (ARs) was found: when AR 9188 emerged, it first started to accumulate positive helicity, while the later neighboring emerging AR 9192 accumulated negative helicity. At a later time, after the bright connecting loops became visible between the two ARs, AR 9188 also suddenly started to gain negative helicity. At the same time AR 9192 started to loose negative helicity. It was found that the magnetic helicity fluxes of the two ARs changed simultaneously by almost the same amount. At one instant it was even possible to determine that the connecting loop between the two ARs carried negative helicity. We excluded the possibility that magnetic flux emergence was causing the observed variation of the magnetic helicity. Hence, magnetic helicity was indeed transferred from the late emerging AR 9192 to AR 9188 via an unbalanced magnetic torque along the loop. Such kinds of helicity transfer might be a common mechanism of redistribution of magnetic helicity in the solar atmosphere, which has just not been widely observed yet.