The standard flare model in three dimensions

Abstract

Context. A standard model for eruptive flares aims at describing observational 3D features of the reconnecting coronal magnetic field. Extensions to the 2D model require the physical understanding of 3D reconnection processes at the origin of the magnetic configuration evolution. However, the properties of 3D reconnection without null point and separatrices still need to be analyzed. Aims. We focus on magnetic reconnection associated with the growth and evolution of a flux rope and associated flare loops during an eruptive flare. We aim at understanding the intrinsic characteristics of 3D reconnection in the presence of quasi-separatrix layers (QSLs), how QSL properties are related to the slip-running reconnection mode in general, and how this applies to eruptive flares in particular. Methods. We studied the slip-running reconnection of field lines in a magnetohydrodynamic simulation of an eruptive flare associated with a torus-unstable flux rope. The squashing degree and the mapping norm are two parameters related to the QSLs. We computed them to investigate their relation with the slip-running reconnection speed of selected field lines. Results. Field lines associated with the flux rope and the flare loops undergo a continuous series of magnetic reconnection, which results in their super-Alfvénic slipping motion. The time profile of their slippage speed and the space distribution of the mapping norm are shown to be strongly correlated. We find that the motion speed is proportional to the mapping norm. Moreover, this slip-running motion becomes faster as the flux rope expands, since the 3D current layer evolves toward a current sheet, and QSLs to separatrices.Conclusions. The present analysis extends our understanding of the 3D slip-running reconnection regime. We identified a controlling parameter of the apparent velocity of field lines while they slip-reconnect, enabling the interpretation of the evolution of post flare loops. This work completes the standard model for flares and eruptions by giving its 3D properties.

Magnetic Nulls and Super-radial Expansion in the Solar Corona

“…The squashing factor is a measure of the distortion of magnetic flux tubes that provides a means of identifying quasi-separatrix layers (QSLs) in a 3D magnetic field (Demoulin et al 1996;Titov et al 2002), and has been extensively used in solar flare analysis to relate photospheric flare ribbons to the topology of the coronal magnetic field (Schmieder et al 1997;Masson et al 2009;Savcheva et al 2012a;Dalmasse et al 2015). QSLs are regions of strong gradients in connectivity of magnetic field lines, and are likely regions for current sheet/layers formation and magnetic reconnection (Aulanier et al 2005;Janvier et al 2013). …”

Simultaneous Observation of a Flux Rope Eruption and Magnetic Reconnection during an X-class Solar Flare

“…With the development of the observational technology, more and more features of magnetic reconnection were reported (Savage et al 2010;Liu et al 2010;Zhang et al 2012;Sun et al 2012;Savage et al 2012aSavage et al , 2012bSu et al 2013;Zhang et al 2013;Deng et al 2013;Dudík et al 2014;Tian et al 2014;Yang, Zhang & Xiang 2015;Sun et al 2015;Xue et al 2016;Li et al 2016;Zhu et al 2016;Li et al 2017;Shen et al 2017). Furthermore, many simulations also show evidence that magnetic reconnection plays an important role in solar eruptions (Antiochos et al 1999, Chen & Shibata 2000, Amari et al 2003, Aulanier et al 2010, Janvier et al 2013Ni et al 2016Ni et al , 2017Mei et al 2017;Jiang et al 2016Jiang et al , 2017.…”

Variations in emission from episodic plasmoid ejecta around black holes

“…The development of solar CMEs involve a sequence of processes (see Török & Kliem 2007;Kliem et al 2010;Chen 2011;Janvier et al 2013). If we ignore the complex details of the MHD, we may divide the plasmoid ejection into two stages: (i) the pre-launch stage and (ii) the launching stage.…”

“…In the CME model for plasmoid ejections modeled in this work, before the full development of the plasmoid and its subsequent ejection, magnetic filaments and flux ropes must have been formed in the accretion disk corona (cf. solar CME formation, see Chen 2011;Janvier et al 2013). Similar to those in the solar corona, these magnetic arcades confine hot thermal plasmas and generate non-thermal energetic charged particles, through shocks within, and plasma and magnetohydrodynamics processes in the interfacing region, where the footpoints of the aracades anchor onto the accretion disk.…”