Greifswald 2024 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 7: Sun and Heliosphere II

EP 7.13: Vortrag

Donnerstag, 29. Februar 2024, 17:30–17:45, ELP 6: HS 2

Flux rope formation prior to CME onset by confined precursor flares---a statistical study — •Bernhard Kliem — University of Potsdam, Institute of Physics and Astronomy

I present a statistical study of flare ribbons in confined eruptions which precede a major ejective eruption (coronal mass ejection, CME), using the complete sample of CMEs associated with > M5.0 flares in 2011--2015 and source distance from Sun center of < 50 deg (32 events, from Baumgartner et al. 2018). Ribbons of precursor events within 12 hr from the onset of the CME-associated (eruptive) flare are compared with the ribbons of the main event to assess a potential contribution of the precursor events to the buildup of a flux rope prior to CME onset. It is found that 26 CMEs (81%) have one or several precursors with bright ribbons that cover a part of the ribbons in the main event, hence, clearly contribute to the buildup of the flux rope that later erupts and drives the CME. Two further events (6%) develop such ribbons during an enhancement that is part of the event's slow-rise phase, i.e., also prior to CME onset. Two CMEs only possess precursors with weak, very short, or very transient ribbons, indicating at least a minor contribution to the buildup of the flux rope erupting in the CME, and the final two events do not show any such indication. Of the last four events, however, three are characterized by a large ribbon separation from their onset, suggesting a high-lying flux rope that may have formed at earlier times. Overall, a significant role of flare reconnection for the buildup of a flux rope prior to CME onset is indicated for the great majority (88%) of the considered CME sample.

Keywords: Sun: coronal mass ejection (CME); Sun: flare; Magnetohydrodynamics