A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions

Abstract

In this article I present a review of recent studies on coronal dynamics, including research progresses on the physics of coronal streamers that are the largest structure in the corona, physics of coronal mass ejections (CMEs) that may cause a global disturbance to the corona, as well as physics of CME-streamer interactions. The following topics will be discussed in depth: (1) acceleration of the slow wind flowing around the streamer considering the effect of magnetic flux tube curvature; (2) physical mechanism accounting for persistent releases of streamer blobs and diagnostic results on the temporal variability of the slow wind speed with such events; (3) force balance analysis and energy release mechanism of CMEs with a flux rope magnetohydrodynamic model; (4) statistical studies on magnetic islands along the coronal-ray structure behind a CME and the first observation of magnetic island coalescence with associated electron acceleration; and (5) white light and radio manifestations of CME-streamer interactions. These studies shed new light on the physics of coronal streamers, the acceleration of the slow wind, the physics of solar eruptions, the physics of magnetic reconnection and associated electron acceleration, the large-scale coronal wave phenomenon, as well as the physics accounting for CME shock-induced type II radio bursts. solar wind, coronal streamer, coronal mass ejection, solar radio burst, magnetic reconnection Citation:Chen Y. A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions.

A Study of Fast Flareless Coronal Mass Ejections

“…It is a core issue of CME studies regarding the release mechanism of magnetic energy in the corona. Two major mechanisms have been suggested including the ideal MHD flux rope instability and magnetic reconnection (see, e.g., Chen et al, 2007aChen et al, , 2007bChen 2013). It is possible that in a specific event both processes contribute.…”

The Possible Role of Coronal Streamers as Magnetically Closed Structures in Shock-Induced Energetic Electrons and Metric Type Ii Radio Bursts

“…Coronal Mass Ejections (CMEs) are observed to be closely related to and frequently interact with helmet streamers (e.g., Howard et al 1985;Hundhausen 1993;McAllister & Hundhausen 1996;Chen et al 2010Chen et al , 2011Feng et al 2011;Chen 2013). In the streamer region, the Alfvénic speed is lower than that of the surroundings because of a much higher plasma density, and the plasma outflow is slow and hardly measurable in the closed magnetic field region (Habbal et al 1997;Strachan et al 2002;Kwon et al 2013;Chen 2013). Due to these special plasma and magnetic conditions, the streamer structure is expected to facilitate the formation and/or enhancement of a CME-driven shock.…”

A solar type II radio burst from CME-coronal ray interaction: simultaneous radio and EUV imaging

“…Secondly, it is expected that when a CME disturbance propagates into a dense coronal structure with low Alfvénic speed, the disturbance may steepen into a shock, or a preexisting shock may get enhanced in strength, also favoring electron acceleration. Thirdly, it is suggested that the closed field topology within the streamer, when swept by an outward-propagating shock, may give rise to a collapsing magnetic trap configuration (Baker et al 1987;Zlobec et al 1993;Somov & Kosugi 1997;Chen 2013), within which electrons are trapped by the upstream field lines, and may return to the shock and be accelerated repeatedly. This also favors the generation of energetic electrons.…”