Transient Coronal Sigmoids and Rotating Erupting Flux Ropes

摘要: To determine the relationship between transient coronal (soft X-ray or EUV) sigmoids and erupting flux ropes, we analyse four events in which a sigmoid could be associated with filament whose apex rotates upon eruption two further phenomena were spatially but not temporally coincident. We find helicity sign of field direction rotation to consistent conversion twist into writhe under ideal MHD constraint conservation, thus supporting our assumption rope topology for rising filament. For positive (negative) clockwise (counterclockwise), taking on reverse (forward) S shape, is opposite that observed sigmoid. This result incompatible models formation: one identifying upward arching kink-unstable ropes current layer oppositely sheared arcades. instead observations agree well model by Titov Demoulin (Astron. Astrophys.351, 707, 1999), identifies steepened layers below ropes.