We performed a three-dimensional MHD simulation of a partially split flux tube emerging into a
solar atmosphere, to investigate the following photospheric and coronal activities: merging of magnetic polarity regions (MPRs) with the same polarity and cancellation of MPRs with opposite polarities (flux cancellation) in the photosphere, both of which are associated with formation of a multiple flux-domain system in the corona. By analyzing the simulated data, we demonstrated how a satellite MPR with a rotating flow in it merged into a main MPR with a counter-rotating flow in it, producing a new main MPR where another rotating flow arose in the same direction as observed in the satellite MPR. In accordance
with the merging process, flux cancellation via U-loop emergence also proceeded in the photosphere. In the corona a current layer separating different flux domains propagated outward as these domains expanded. We also examined injection of magnetic
flux, magnetic energy, and relative magnetic helicity into the atmosphere by the partially split flux tube, presenting a physical explanation of temporal development of mutual magnetic helicity in the multiple flux-domain system.
Reference
Magara, T.
2008 PASJ, 60, 809
PFL represents "peak flux location" (not principal field line). PFL I (II) represents main (satellite) MPR.
