Evolution of a filament due to magnetic-field variations in a complex active region

Abstract

Abstract-The complex active region NOAA 9672 is studied when it was near the central meridian, from October 21-26, 2001. At that time, there was an emergence of new magnetic flux, with the ongoing formation of a filament. The dynamics of the magnetic field are studied in order to search for their possible manifestations in the filament structure, using SOHO MDI magnetograms, SOHO EIT and TRACE filtergrams in the 171Å line, and Hα filtergrams available via the Internet. Our earlier conclusion that filaments form at the boundaries of supergranules near polarity-inversion lines is confirmed. The conclusion of Chae that sinistral filaments have positive magnetic helicity is also confirmed. New information about magnetic-field decay processes is obtained. The direction of motion of the magnetic poles and their relative positions suggest that the axial field of a filament forms as a result of either reconnection of cancelling magnetic poles, or emergence of horizontal magnetic-flux tubes.PACS numbers : 96.60.R

The eruption of a small filament in the quiet Sun

“…Filament disturbance may be closely correlated with corresponding changes of the magnetic environment (Schmieder 1990). As for large-scale filaments in both quiet and active regions, some previous studies have shown that their disturbances can be greatly contributed to flux emergences and cancellations (Rust et al 1975;Wang et al 1996;Chen and Shibata 2000;Wang 2000, 2001;Moore et al 2001;Zhang et al 2001;Kim et al 2001;Moon et al 2004;Grigor'ev et al 2006;Archontis and Hood 2008). On the other hand, although the relationship between photospheric magnetic activities and small-scale filament eruptions have been studied only in a few cases (Hermans and Martin 1986;Sakajiri et al 2004;Zuccarello et al 2007), it appears that flux emergences and cancellations, like in the large-scale cases, play important roles in disturbing small filaments.…”