Understanding the Initiation of the M2.4 Flare on 2017 July 14

We present both the observation and the magnetohydrodynamics (MHD) simulation of the M2.4 flare (SOL2017-07-14T02:09) of NOAA active region (AR) 12665 with a goal to identify its initiation mechanism. The observation by the Atmospheric Image Assembly (AIA) on board the Solar Dynamics Observatory (SDO) shows that the major topology of the AR is a sigmoidal configuration associated with a filament/flux rope. A persistent emerging magnetic flux and the rotation of the sunspot in the core region were observed with Magnetic Imager (HMI) on board the SDO on the timescale of hours before and during the flare, which may provide free magnetic energy needed for the flare/coronal mass ejection (CME). A high-lying coronal loop is seen moving outward in AIA EUV passbands, which is immediately followed by the impulsive phase of the flare. We perform an MHD simulation using the potential magnetic field extrapolated from the measured pre-flare photospheric magnetic field as initial conditions and adopting the observed sunspot rotation and flux emergence as the driving boundary conditions. In our simulation, a sigmoidal magnetic structure and an overlying magnetic flux rope (MFR) form as a response to the imposed sunspot rotation, and the MFR rises to erupt like a CME. These simulation results in good agreement with the observation suggest that the formation of the MFR due to the sunspot rotation and the resulting torus and kink instabilities were essential to the initiation of this flare and the associated coronal mass ejection.

[1]  G. Fleishman,et al.  Force-free Field Reconstructions Enhanced by Chromospheric Magnetic Field Data , 2018, The Astrophysical Journal.

[2]  Chang Liu,et al.  Statistical Analysis of Torus and Kink Instabilities in Solar Eruptions , 2018, The Astrophysical Journal.

[3]  F. Alauzet,et al.  Magnetic cage and rope as the key for solar eruptions , 2018, Nature.

[4]  B. Welsch.  Flux Accretion and Coronal Mass Ejection Dynamics , 2017, Solar Physics.

[5]  K. Kusano,et al.  Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism , 2017, 1706.07153.

[6]  S. Antiochos,et al.  A universal model for solar eruptions , 2017, Nature.

[7]  Chang Liu,et al.  High-resolution observations of flare precursors in the low solar atmosphere , 2017, Nature Astronomy.

[8]  A. Stupishin,et al.  Casting the Coronal Magnetic Field Reconstruction Tools in 3D Using the MHD Bifrost Model , 2017, 1703.06360.

[9]  Chang Liu,et al.  Flare differentially rotates sunspot on Sun's surface , 2016, Nature Communications.

[10]  K. Kusano,et al.  Double Arc Instability in the Solar Corona , 2016, 1706.06112.

[11]  H. Ji,et al.  A dynamic magnetic tension force as the cause of failed solar eruptions , 2015, Nature.

[12]  J. T. Hoeksema,et al.  The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs – Space-Weather HMI Active Region Patches , 2014, 1404.1879.

[13]  L. Driel-Gesztelyi,et al.  Initiation of Coronal Mass Ejections by Sunspot Rotation , 2013, Proceedings of the International Astronomical Union.

[14]  C. J. Wolfson,et al.  Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO) , 2012 .

[15]  K. Shibata,et al.  Solar Flares: Magnetohydrodynamic Processes , 2011 .

[16]  C. J. Wolfson,et al.  The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) , 2011 .

[17]  Y. Fan,et al.  Onset of Coronal Mass Ejections Due to Loss of Confinement of Coronal Flux Ropes , 2007 .

[18]  J. Zhang,et al.  A Statistical Study of Main and Residual Accelerations of Coronal Mass Ejections , 2006 .

[19]  W. Thompson.  Coordinate systems for solar image data , 2006 .

[20]  T. Török,et al.  Confined and Ejective Eruptions of Kink-unstable Flux Ropes , 2005, astro-ph/0507662.

[21]  E. Priest,et al.  The magnetic nature of solar flares , 2002 .

[22]  H. Hudson,et al.  Onset of the Magnetic Explosion in Solar Flares and Coronal Mass Ejections , 2001 .

[23]  S. Antiochos,et al.  A Model for Solar Coronal Mass Ejections , 1998, astro-ph/9807220.

[24]  Michael S. Wheatland,et al.  An Optimization Approach to Reconstructing Force-free Fields , 1997 .

[25]  P. Sturrock.  Model of the High-Energy Phase of Solar Flares , 1966, Nature.

[26]  J. Evershed.  Radial movement in sun-spots , 1909 .