Probing Twisted Magnetic Field Using Microwave Observations in an M Class Solar Flare on 11 February, 2014

Abstract

This work demonstrates the possibility of magnetic field topology investigations using microwave polarimetric observations. We study a solar flare of GOES M1.7 class that occurred on 11 February, 2014. This flare revealed a clear signature of spatial inversion of the radio emission polarization sign. We show that the observed polarization pattern can be explained by nonthermal gyrosynchrotron emission from the twisted magnetic structure. Using observations of the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Observatory, Radio Solar Telescope Network, and Solar Dynamics Observatory, we have determined the parameters of nonthermal electrons and thermal plasma and identified the magnetic structure where the flare energy release occurred. To reconstruct the coronal magnetic field, we use nonlinear force-free field (NLFFF) and potential magnetic field approaches. Radio emission of nonthermal electrons is simulated by the GX Simulator code using the extrapolated magnetic field and the parameters of nonthermal electrons and thermal plasma inferred from the observations; the model radio maps and spectra are compared with observations. We have found that the potential magnetic field approach fails to explain the observed circular polarization pattern; on the other hand, the Stokes $V$ map is successfully explained by assuming nonthermal electrons to be distributed along the twisted magnetic structure determined by the NLFFF extrapolation approach. Thus, we show that the radio polarization maps can be used for diagnosing the topology of the flare magnetic structures where nonthermal electrons are injected.

References in corpus (10)

• Size dependence of solar X-ray flare properties
• 3D Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity
• Particle acceleration and transport in reconnecting twisted loops in a stratified atmosphere
• Evolution of the Loop-Top Source of Solar Flares--Heating and Cooling Processes
• Properties of the Acceleration Regions in Several Loop-structured Solar Flares
• 3D simulations of gyrosynchrotron emission from mildly anisotropic nonuniform electron distributions in symmetric magnetic loops
• Effect of collisions and magnetic convergence on electron acceleration and transport in reconnecting twisted solar flare loops
• Thermal and non-thermal emission from reconnecting twisted coronal loops
• Polarisation of microwave emission from reconnecting twisted coronal loops
• Modelling of Nonthermal Microwave Emission From Twisted Magnetic Loops

Cited by in corpus (4)

• The Low-Frequency Solar Corona in Circular Polarization
• Combining MHD and kinetic modelling of solar flares
• Discovery of correlated evolution in solar noise storm source parameters: Insights on magnetic field dynamics during a microflare
• Pulsations of microwave emission from a solar flare in a twisted loop caused by intrinsic MHD oscillations