Observational Evidence of Particle Acceleration Associated With Plasmoid Motions

Abstract

We report a strong association between the particle acceleration and plasma motions found in the 2010 August 18 solar flare. The plasma motions are tracked in the extreme-ultraviolet (EUV) images taken by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Extreme Ul-traViolet Imager (EUVI) on the Solar Terrestrial Relation Observatory spacecraft Ahead, and the signature of particle acceleration was investigated by using Nobeyama Radioheliograph data. In our previous paper, we reported that in EUV images many plasma blobs appeared in the current sheet above the flare arcade. They were ejected bidirectionally along the current sheet, and the blobs that were ejected sunward collided with the flare arcade. Some of them collided or merged with each other before they were ejected from the current sheet.We discovered impulsive radio bursts associated with such plasma motions (ejection, coalescence, and collision with the post flare loops). The radio bursts are considered to be the gyrosynchrotron radiation by nonthermal high energy electrons. In addition, the stereoscopic observation by AIA and EUVI suggests that plasma blobs had a three-dimensionally elongated structure. We consider that the plasma blobs were three-dimensional plasmoids (i.e. flux ropes) moving in a current sheet. We believe that our observation provides clear evidence of particle acceleration associated with the plasmoid motions. We discuss possible acceleration mechanisms on the basis of our results.

The First ALMA Observation of a Solar Plasmoid Ejection from an X-Ray Bright Point

“…Eruptions are one of the key mechanisms of explosive energy release in the solar atmosphere. Since magnetic reconnection models predict that ejections of magnetic islands from current sheets accompany fast magnetic reconnection (e.g., Priest 1985;Shibata & Tanuma 2001;Bhattacharjee, et al 2009), plasmoid ejection from flare sites have been investigated intensively (e.g., Shibata, et al 1995;Ohyama & Shibata 1998;Hudson, et al 2001;Takasao, et al 2016). Observationally, an ejected plasmoid is identified as a moving bright blob, sometimes embedded in another plasma flow such as a coronal jet (Alexander & Fletcher 1999).…”

Development of Turbulent Magnetic Reconnection in a Magnetic Island

“…The generation of magnetic islands isusually accompanied in such a process bya topological change of magnetic field lines (Wang et al 2010;Daughton et al 2011;Dong et al 2012), and their roles inmagnetic reconnection have recently been paid more and more attention. Magnetic islandscan enhance not only the reconnection rate (Daughton et al 2006;Bhattacharjee et al 2009) but also the efficiency of particle acceleration (Drake et al 2006a;Fu et al 2006;Chen et al 2008;Guo et al 2014;Takasao et al 2016). Plasma particles can gain energy as they are reflected from two ends of a contracting magnetic island (Drake et al 2006a;Fu et al 2006).…”

Initiation of Coronal Mass Ejection Event Observed on 2010 November 3: Multi-Wavelength Perspective

“…There have been numerous indirect evidences for the reconnection phenomena such as reconnection inflow (Yokoyama et al 2001;Savage et al 2012;Takasao et al 2012) and reconnection outflow Hudson 1999, 2001;Tripathi et al 2006bTripathi et al , 2007Savage et al 2010), non-thermal hard X-ray sources associated with initiation of CMEs Chifor et al (2006). However, these different signatures have been observed individually in separate dynamic events.…”