Rotation of an erupting filament observed by the STEREO EUVI and COR1 instruments

Abstract

On August 31, 2007, a prominence eruption was observed by the Solar TErrestrial RElations Observatory (STEREO) in the ExtremeUltraViolet Imager (EUVI) 304 images and later on, as the core of a three-part coronal mass ejection (CME) in images acquired by the inner STEREO coronagraph (COR1). Because they were covered by both STEREO spacecraft from right vantage points, these observations provide an excellent opportunity to perform a three-dimensional (3D) prominence reconstruction and study its evolution. We employed the tie-pointing technique to reconstruct the 3D shape and trajectory of the prominence, which has been followed from an heliocentric distance of ∼1.3 up to ∼2.4 R during the first 1.3 h of eruption. Data show evidence for a progressive clockwise prominence rotation by ∼90 • occurring not only in the early phase of the eruption sampled by EUVI, but also at larger heliocentric distances as seen by COR1. Interestingly, a counter-clockwise rotation of the filament was observed in Hα images in the week before the eruption; the filament does not show a twisted shape. In the same period, the potential field extrapolated at different times shows a clockwise rotation of closed lines overlying the filament. This suggests that a magnetic helicity storage occurred not in the filament itself, but in the global magnetic field configuration of the surrounding corona. Moreover, close inspection to the high-resolution EUVI images revealed a small scale helical feature along the erupting prominence. The sense of rotation of this helix agrees with the observed prominence rotation, providing evidence for the conversion of twist into writhe. The observed rotation of an erupting prominence, if representative of the flux rope rotation, may have a strong impact on the definition of geo-effectiveness of CMEs for space weather forecasting purposes.

Coronal Mass Ejections: Observations

“…They found evidence of two different motions, a helical twist in the prominence spine and overall non-radial equatorward motion of the entire prominence structure, and two phases of acceleration during the eruptions. Bemporad et al (2011) used the tie-pointing technique with COR1 and EUVI data to reconstruct the 3-D shape and trajectory of an erupting prominence. They found evidence for a progressive clockwise rotation of the prominence by ∼ 90°, and helical motion providing evidence for the conversion of twist into writhe.…”

Effect of gravitational stratification on the propagation of a CME

“…Some recent work that describes the propagation of CMEs in the solar corona include Gopalswamy et al (2012) and Bemporad et al (2011). Other studies give diverse examples of how the CME propagation can be modified according to the environment where it develops; e.g., Temmer et al (2012) describe the interaction of a CME with another CME that preceded it.…”

Rotating Motions and Modeling of the Erupting Solar Polar-Crown Prominence on 2010 December 6

“…Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise (e.g., Kurokawa et al 1987;Ji et al 2003;Zhou et al 2006;Green et al 2007;Liu et al 2007;Liu & Alexander 2009;Muglach et al 2009;Bemporad et al 2011;Thompson 2011). This filament rotation is interpreted as a conversion of twist into writhe in a kink-unstable flux rope.…”

“…Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Helicity is a quantitative, mathematical measure of chirality (Berger & Field 1984;Muglach et al 2009;Bemporad et al 2011). Magnetic reconnection with the ambient field can also cause filament rotation during eruption (Cohen et al 2010;Thompson 2011).…”