Does Flare Reconnection Occur Before or After Explosive Coronal Mass Ejection Acceleration?
Abstract
The mechanism for producing fast coronal mass ejections/eruptive flares (CME/EFs) is hotly debated. Most models rely on ideal instability/loss of equilibrium or magnetic reconnection; these two categories of models predict different causal relationships between CMEs and flares. In both cases, flare reconnection disconnects the bulk of the CME from the Sun, but in the former models, flare reconnection onset is a consequence of the fast outward motion of the CME while in the later models reconnection is what causes the CME acceleration. Discriminating between these models requires continuous, high-cadence observations and state-of-the-art numerical simulations that enable the relative timing of key stages in the events to be determined. With the advent of SDO, STEREO, and massively parallel supercomputers, we are well poised to tackle this major challenge to our understanding of solar activity. In recent work (Karpen et al. 2012), we determined the timing and location of triggering mechanisms for the breakout initiation model (Antiochos et al. 1999), using ultra-high-resolution magnetohydrodynamic simulations with adaptive mesh refinement and high-cadence analysis. This approach enabled us to resolve as finely as possible the small scales of magnetic reconnection and island formation in the current sheets, within the global context of a large-scale solar eruption. We found that the explosive acceleration of the fast CME occurs only after the onset of rapid reconnection at the flare current sheet formed in the wake of the rising CME flux rope. In the present work, we compare flare reconnection rates, measured from flare ribbon UV brightenings observed by SDO/AIA and magnetograms from SDO/HMI, with the height evolution of CME fronts and cores, measured from STEREO/SECCHI EUV and coronagraph images. We also calculate these quantities from numerical simulations and compare them to observations, as a new test of the breakout initiation model. This work was supported by NASA's Heliophysics Supporting Research and Living With a Star Targeted Research and Technology programs.
- Publication:
-
AAS/AGU Triennial Earth-Sun Summit
- Pub Date:
- April 2015
- Bibcode:
- 2015TESS....110704G