Evolution of Plasma Composition in an Eruptive Flux Rope

D. Baker, L. M. Green, D. H. Brooks, P. Démoulin, L. van Driel-Gesztelyi, T. Mihailescu, A. S. H. To, D. M. Long, S. L. Yardley, M. Janvier, G. Valori

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level.
Original languageEnglish
Article number17
Pages (from-to)1-12
Number of pages12
JournalThe Astrophysical Journal
Volume924
Issue number1
Early online date6 Jan 2022
DOIs
Publication statusPublished - Jan 2022
Externally publishedYes

Cite this