English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present evidence that a magnetic flux rope was formed before a coronalmass ejection (CME) and its associated long-duration flare during a pair ofpreceding confined eruptions and associated impulsive flares in a compoundevent in NOAA Active Region 12371. Extreme-ultraviolet images and theextrapolated nonlinear force-free field show that the first two, impulsiveflares, SOL2015-06-21T01:42, result from the confined eruption of highlysheared low-lying flux, presumably a seed flux rope. The eruption spawns avertical current sheet, where magnetic reconnection creates flare ribbons andloops, a nonthermal microwave source, and a sigmoidal hot channel which canonly be interpreted as a magnetic flux rope. Until the subsequent long-durationflare, SOL2015-06-21T02:36, the sigmoid's elbows expand, while its centerremains stationary, suggesting non-equilibrium but not yet instability. The"flare reconnection" during the confined eruptions acts like "tether-cuttingreconnection" whose flux feeding of the rope leads to instability. Thesubsequent full eruption is seen as an accelerated rise of the entire hotchannel, seamlessly evolving into the fast halo CME. Both the confined andejective eruptions are consistent with the onset of the torus instability inthe dipped decay index profile which results from the region's two-scalemagnetic structure. We suggest that the formation or enhancement of anon-equilibrium but stable flux rope by confined eruptions is a generic processoccurring prior to many CMEs.

Non-equilibrium Flux Rope Formation by Confined Flares Preceding a Solar Coronal Mass Ejection