MHD turbulence formation in solar flares: 3D simulation and synthetic observations

Abstract

Turbulent plasma motion is common in the universe, and invoked in solar flares to drive effective acceleration leading to high energy electrons. Unresolved mass motions are frequently detected in flares from extreme ultraviolet (EUV) observations, which are often regarded as turbulence. However, how this plasma turbulence forms during the flare is still largely a mystery. Here we successfully reproduce observed turbulence in our 3D magnetohydrodynamic simulation where the magnetic reconnection process is included. The turbulence forms as a result of an intricate non-linear interaction between the reconnection outflows and the magnetic arcades below the reconnection site, in which the shear-flow driven Kelvin-Helmholtz Instability (KHI) plays a key role for generating turbulent vortices. The turbulence is produced above high density flare loops, and then propagates to chromospheric footpoints along the magnetic field as Alfvenic perturbations. High turbulent velocities above 200 km s^-1 can be found around the termination shock, while the low atmosphere reaches turbulent velocities of 10 km s^-1 at a layer where the number density is about 10^11 cm^-3. The turbulent region with maximum non-thermal velocity coincides with the region where the observed high-energy electrons are concentrated, demonstrating the potential role of turbulence in acceleration. Synthetic views in EUV and fitted Hinode-EIS spectra show excellent agreement with observational results. An energy analysis demonstrates that more than 10% of the reconnection downflow kinetic energy can be converted to turbulent energy via KHI.

References in corpus (13)

• Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem
• Measurement of magnetic field and relativistic electrons along a solar flare current sheet
• Global Energetics of Solar Flares: V. Energy Closure in Flares and Coronal Mass Ejections
• Fine strand-like structure in the solar corona from MHD transverse oscillations
• Propagation of Alfvénic Waves From Corona to Chromosphere and Consequences for Solar Flares
• The Origin of Underdense Plasma Downflows Associated with Magnetic Reconnection in Solar Flares
• The development of lower-atmosphere turbulence early in a solar flare
• A fully self-consistent model for solar flares
• Transition region adaptive conduction (TRAC) in multidimensional magnetohydrodynamic simulations
• The Spatial and Temporal Variations of Turbulence in a Solar Flare
• When hot meets cold: post-flare coronal rain
• Footpoint versus loop-top hard X-ray emission sources in solar flares
• Current-sheet Oscillations Caused by Kelvin-Helmholtz Instability at the Loop Top of Solar Flares

Cited by in corpus (9)

• Three-dimensional Turbulent Reconnection within Solar Flare Current Sheet
• Two-fluid reconnection jets in a gravitationally stratified atmosphere
• Alfvén Waves in Solar Flares
• Solar Flare Ion Temperatures
• Nonthermal electron acceleration in turbulent post-flare coronal loops
• Solar flare ribbons structured by uncombed chromospheric loops
• Radiation-magnetohydrodynamics with MPI-AMRVAC using flux-limited diffusion
• Numerical Investigation of Efficient Electron Acceleration at an Unsteady Solar Flare Loop-Top
• Transport of electrons in tangled magnetic fields