3D simulations of gyrosynchrotron emission from mildly anisotropic nonuniform electron distributions in symmetric magnetic loops

Abstract

Microwave emission of solar flares is formed primarily by incoherent gyrosynchrotron radiation generated by accelerated electrons in coronal magnetic loops. The resulting emission depends on many factors, including pitch-angle distribution of the emitting electrons and the source geometry. In this work, we perform systematic simulations of solar microwave emission using recently developed tools (GS Simulator and fast gyrosynchrotron codes) capable of simulating maps of radio brightness and polarization as well as spatially resolved emission spectra. A 3D model of a symmetric dipole magnetic loop is used. We compare the emission from isotropic and anisotropic (of loss-cone type) electron distributions. We also investigate effects caused by inhomogeneous distribution of the emitting particles along the loop. It is found that effect of the adopted moderate electron anisotropy is the most pronounced near the footpoints and it also depends strongly on the loop orientation. Concentration of the emitting particles at the loop top results in a corresponding spatial shift of the radio brightness peak, thus reducing effects of the anisotropy. The high-frequency (around 50 GHz) emission spectral index is specified mainly by the energy spectrum of the emitting electrons; however, at intermediate frequencies (around 10-20 GHz), the spectrum shape is strongly dependent on the electron anisotropy, spatial distribution, and magnetic field nonuniformity. The implications of the obtained results for the diagnostics of the energetic electrons in solar flares are discussed.

ApJ in press. 20 pp, 13 figs, on-line album and simulation source code available

References in corpus (4)

• Broadband Quasi-Periodic Radio and X-ray Pulsations in a Solar Flare
• Radio Spectral Evolution of an X-ray Poor Impulsive Solar Flare: Implications for Plasma Heating and Electron Acceleration
• Broadband microwave burst produced by electron beams
• Kinetic Simulation of the Electron-Cyclotron Maser Instability: Relaxation of Electron Horseshoe Distributions

Cited by in corpus (27)

• Solar science with the Atacama Large Millimeter/submillimeter Array - A new view of our Sun
• 3D Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity
• Solar Physics with the Square Kilometre Array
• A Cold Flare With Delayed Heating
• Modeling of gyrosynchrotron radio emission pulsations produced by MHD loop oscillations in solar flares
• Thermal to Nonthermal Energy Partition at the Early Rise Phase of Solar Flares
• Radio, Hard X-Ray, and Gamma-Ray Emissions Associated with a Far-Side Solar Event
• Energy Partitions and Evolution in a Purely Thermal Solar Flare
• Time-variable non-thermal emission in the planetary nebula IRAS 15103-5754
• Spatially-resolved Energetic Electron Properties for the 21 May 2004 Flare from Radio Observations and 3D Simulations
• The first flare observation with a new solar microwave spectrometer working in 35-40 GHz
• Simulations of Gyrosynchrotron Microwave Emission from an Oscillating 3D Magnetic Loop
• Probing Dynamics of Electron Acceleration with Radio and X-ray Spectroscopy, Imaging, and Timing in the 2002 Apr 11 Solar Flare
• The 26 December 2001 Solar Eruptive Event Responsible for GLE63. II. Multi-Loop Structure of Microwave Sources in a Major Long-Duration flare
• The coronal volume of energetic particles in solar flares as revealed by microwave imaging
• Validation Of The Coronal Thick Target Source Model
• Modelling the environment around five ultracool dwarfs via the radio domain
• Polarisation of microwave emission from reconnecting twisted coronal loops
• Solar Burst Analysis with 3D Loop Models
• Excitation of Multi-periodic Kink Motions in Solar Flare Loops: Possible Application to Quasi-periodic Pulsations
• Predicting the time variation of radio emission from MHD simulations of a flaring T-Tauri star
• Spectropolarimetric Radio Imaging of Faint Gyrosynchrotron Emission from a CME : A Possible Indication of the Insufficiency of Homogeneous Models
• The 26 December 2001 Solar Event Responsible for GLE63. I. Observations of a Major Long-Duration Flare with the Siberian Solar Radio Telescope
• Modelling of Nonthermal Microwave Emission From Twisted Magnetic Loops
• Probing Twisted Magnetic Field Using Microwave Observations in an M Class Solar Flare on 11 February, 2014
• Influence of fine structures on gyrosynchrotron emission of flare loops modulated by sausage modes
• Thyr: A Volumetric Ray-Marching Tool for Simulating Microwave Emission