Observational Evidence of the Kink Instability In Solar Eruptions

Two approaches to studying the role of source region magnetic fields for CMEs are described. First, observational evidence is used to infer that the MHD helical kink instability is associated with at least some filament eruptions and CMEs. In seven cases, the sense of twist and writhe in the source regions were determined from movies of erupting filaments. In every case the sense of twist was the same as the sense of writhe, as required for a kink. Next, we consider six different cases in which the chirality and axis orientation of interplanetary flux ropes could be compared with the corresponding signatures in the source regions at the Sun. In four cases, the chirality and orientation inferred from these pre-eruption flux rope signatures agreed well with the interplanetary flux rope signatures. In two cases, the flux rope axis orientations differed by about 150 degrees. These results suggest that the flux ropes existed prior to eruption, that they become flux ropes in interplanetary space, and, at least in some cases, that the kink instability is the likely cause of eruption.