Evidence for the Magnetic Breakout Model in an Equatorial Coronal-Hole Jet
Abstract
We have analyzed an equatorial coronal-hole jet observed by SDO/AIA on 09 January 2014. The source-region magnetic field structure is consistent with the embedded-bipole topology that we identified and modeled previously as a source of coronal jets (Pariat et al. 2009, 2010, 2015, 2016; Karpen et al. 2017; Wyper et al. 2016). Initial brightenings were observed below a small but distinct “mini-filament” about 25 min before jet onset. A bright circular structure, interpreted as magnetic flux rope (MFR), surrounded the mini-filament. The MFR and filament rose together slowly at first, with a speed of ∼15 km s-1. When bright footpoints and loops appeared below, analogous to flare ribbons and arcade, the MFR/mini-filament rose rapidly (∼126 km s-1), and a bright elongated feature interpreted as a current sheet appeared between the MFR and the growing arcade. Multiple plasmoids propagating upward (∼135 km s-1) and downward (∼55 km s-1) were detected in this sheet. The jet was triggered when the rising MFR interacted with the overlying magnetic structure, most likely at a stressed magnetic null distorted into a current sheet. This event thus exhibits clear evidence of “flare” reconnection below the MFR as well as breakout reconnection above it, consistent with the breakout model for a wide range of solar eruptions (Antiochos et al. 1999; Devore & Antiochos 2008; Karpen et al. 2012; Wyper et al. 2017). Breakout reconnection destroyed the MFR and enabled the entrained coronal plasma and mini-filament to escape onto open field lines, producing an untwisting jet. SDO/HMI magnetograms reveal small footpoint motions at the eruption site and its surroundings, but do not show significant flux emergence or cancellation during or 1-2 hours before the eruption. Therefore, the free energy powering this jet most likely originated in magnetic shear concentrated at the polarity inversion line within the embedded bipole - a mini-filament channel - possibly created by helicity condensation (Antiochos 2013; Knizhnik et al. 2015, 2017).This work was supported in part by a grant from the NASA H-SR program and the NASA Postdoctoral Program.
- Publication:
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AAS/Solar Physics Division Abstracts #48
- Pub Date:
- August 2017
- Bibcode:
- 2017SPD....4820303K