Evidence of a Plasmoid-Looptop Interaction and Magnetic Inflows During a Solar Flare/CME Eruptive Event

TL;DR

This paper presents multi-instrument observational evidence of plasmoid-looptop merging, magnetic inflows, and associated particle acceleration during a solar flare and CME event, supporting recent numerical models of tearing mode instability.

Contribution

It provides the first detailed observational confirmation of plasmoid-looptop interactions and inflow dynamics during a solar eruptive event, linking these processes to particle acceleration.

Findings

Enhanced nonthermal emission during plasmoid merging

Downward plasmoid velocity of 12 km/s

Magnetic inflow velocity of 1.5 km/s

Abstract

Observational evidence is presented for the merging of a downward-propagating plasmoid with a looptop kernel during an occulted limb event on 2007 January 25. RHESSI lightcurves in the 9-18 keV energy range, as well as that of the 245 MHz channel of the Learmonth Solar Observatory, show enhanced nonthermal emission in the corona at the time of the merging suggesting that additional particle acceleration took place. This was attributed to a secondary episode of reconnection in the current sheet that formed between the two merging sources. RHESSI images were used to establish a mean downward velocity of the plasmoid of 12 km/s. Complementary observations from the SECCHI suite of instruments onboard STEREO-Behind showed that this process occurred during the acceleration phase of the associated CME. From wavelet-enhanced EUVI, images evidence of inflowing magnetic field lines prior to the CME eruption is also presented. The derived inflow velocity was found to be 1.5 km/s. This combination of observations supports a recent numerical simulation of plasmoid formation, propagation and subsequent particle acceleration due to the tearing mode instability during current sheet formation.