Abstract
Abstract. On 10–11 December 2005 a slow CME occurred in the Western Hemisphere in between two coronal streamers. SOHO/MDI magnetograms show a multipolar magnetic configuration at the photosphere: a complex of active regions located at the CME source and two bipoles at the base of the lateral coronal streamers. White light observations reveal that the CME expansion affects both of them and induces the release of plasma within or close to the nearby streamers. These transient phenomena are possibly due to magnetic reconnections induced by the CME expansion and occurring inside the streamer current sheet or between the CME flanks and the streamer. These events have been observed by the SOHO/UVCS with the spectrometer slit centered at 1.8 R⊙ over about a full day. In this work we focus on the interaction between the CME and the streamer: the UVCS spectral interval included UV lines from ions at different temperatures of maximum formation such as O VI, Si XIII and Al Xi. These data gave us the opportunity to infer the evolution of plasma temperature and density at the reconnection site and adjacent regions. These are relevant to characterize secondary reconnection processes occurring during a CME development.
Highlights
White light images acquired in the last ten years by the Large Angle and Spectrometric COronagraphs (LASCO; Brueckner et al, 1995) on SOHO demonstrated that the occurrence of a Coronal Mass Ejection quite often is followed by the formation of one or more radial features connecting the CME to the solar surface, some of them being identified as the CME flanks
White light images acquired in the last ten years by the Large Angle and Spectrometric COronagraphs (LASCO; Brueckner et al, 1995) on SOHO demonstrated that the occurrence of a Coronal Mass Ejection quite often is Correspondence to: A
Despite the complexity reached by the actual CME models, so far little is known about the role played by nearby coronal structures and in general by the overall coronal magnetic configuration in the CME occurrence, recent UV and radio observations of flare associated CMEs suggest that the magnetic reconnection occurring between an expanding magnetic structure and nearby open fields can play a role in the eruption development (Goff et al, 2007; Demoulin et al, 2007)
Summary
LASCO data suggest that the catastrophe loss of equilibrium can be the primary driver of CMEs (see e.g. Liu et al, 2003) and the catastrophe CME models (e.g. Lin and Forbes, 2000) predicted the formation of a current sheet connecting the top of the reconnecting post-eruption loops with the bottom of the expanding plasma bubble. Lin and Forbes, 2000) predicted the formation of a current sheet connecting the top of the reconnecting post-eruption loops with the bottom of the expanding plasma bubble. These models start from a simple bipolar magnetic configuration, while observations indicate that the CME occurrence is associated with much more complex magnetic topologies. Despite the complexity reached by the actual CME models, so far little is known about the role played by nearby coronal structures (e.g. two lateral streamers in the case of a quadrupolar configuration) and in general by the overall coronal magnetic configuration in the CME occurrence, recent UV and radio observations of flare associated CMEs suggest that the magnetic reconnection occurring between an expanding magnetic structure and nearby open fields can play a role in the eruption development (Goff et al, 2007; Demoulin et al, 2007). We show how the same phenomena have been observed at 1.8 R in the UV lines
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