“Twisting” Motions in Erupting Coronal Pseudostreamers as Evidence for Interchange Reconnection

Abstract

Abstract Using white-light observations from the COR1 coronagraph during 2008–2013, we have identified ∼50 eruptive events in which a narrow streamer structure appears to rotate about its radial axis as it rises into the field of view beyond . Extreme-ultraviolet images and potential-field extrapolations suggest that most of these eruptions involve one arcade of a double-lobed pseudostreamer, which is surrounded by open flux of a single polarity. The “twisting” is manifested by the cavity of the erupting lobe, which evolves from a circular to a narrowing oval structure as it is ejected nonradially in the direction of the original X-point. At the same time, the loop legs on the trailing side of the rising cavity/flux rope expand and straighten out, starting at the outer edge of the lobe and progressing inward; this asymmetric opening-up contributes to the impression of a three-dimensional structure twisting away from the observer. On the leading side of the lobe, collapsing cusps are sometimes detected, suggesting the presence of a current sheet where the cavity loops reconnect with the oppositely directed open flux from the adjacent coronal hole. In some events, the inner loops of the cavity/flux rope may continue to expand outward without undergoing interchange reconnection. The transfer of material to open field lines, as well as the lateral confinement of the pseudostreamer by the surrounding coronal holes, acts to produce a relatively narrow, fan-like ejection that differs fundamentally from the large, bubble-shaped ejections associated with helmet streamers.