Half-turn rotation of polarity inversion line associated with formation of quadrupolar-like structure via flux emergence
We performed a three-dimensional MHD simulation for reproducing emergence of a twisted flux tube to investigate half-turn rotation of a neutral line or polarity inversion line (PIL) in a solar surface. When it emerged, the flux tube first produced a bipolar region with the PIL in the surface, followed by the half-turn rotation of the PIL associated with formation of quadrupolar-like structure. The magnetic field configuration in this structure is reminiscent of, but essentially different from the so-called inverse-polarity configuration proposed for magnetic structure of a solar filament/prominence. The physical mechanism for producing the half-turn rotation of the PIL was identified as W-loop emergence which may play a key role in stabilizing the magnetic structure of the filament/prominence.
Reference
Magara, T. et al. 2011 JKAS, 44, 143
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Formation of quadrupolar-like structure in solar atmosphere via W-loop emergence. In the left movie inner and outer field lines of emerging flux tube are drawn in blue and red, respectively. The inner field lines compose flux rope, while the outer field lines become Ω-loops overlying the flux rope and W-loops underlying the flux rope (see also pre-eruptive magnetic structure). In the right movie red arrows represent transverse component of surface magnetic field, while the gray-scale map shows distribution of vertical magnetic flux density in the surface. The PIL rotates as the W-loop emergence proceeds.
