Magnetic Helicity Injection During the Formation of an Intermediate Filament

Abstract

A necessary condition for the formation of a filament is magnetic helicity. In the present paper we seek the origin of magnetic helicity of intermediate filaments. We observed the formation of a sinistral filament at the boundary of a decaying active region using full-disk H α images obtained from Big Bear Solar Observatory. We have measured the rate of helicity injection during the formation of the filament using full-disk 96 minute-cadence magnetograms taken by SOHO MDI. As a result we found that 1) no significant helicity was injected around the region (polarity inversion line; PIL) of filament formation and 2) negative helicity was injected in the decaying active region. The negative sign of the injected helicity was opposite to that of the filament helicity. On the other hand, at earlier times when the associated active region emerged and grew, positive helicity was intensively injected. Our results suggest that the magnetic helicity of the intermediate filament may have originated from the helicity accumulated during the period of the growth of its associated active region.

Formation and Large-Scale Patterns of Filament Channels and Filaments

“…It is clear from the observations that this filament is of EBR type and reconfiguration of the previously emerged fields played a critical role in the formation of the filament. In the recent paper of Jeong et al (2009) the authors present observations that support the idea that the non-potential fields and helicity of IF's originate during the emergence of activity complexes. Gaizauskas et al (2001) described a similar process of filament channel and filament formation between two neighboring activity complexes, but this time for a QF which is nearly 1R ⊙ in length.…”