Thyr: A Volumetric Ray-Marching Tool for Simulating Microwave Emission

Abstract

Gyrosynchrotron radiation is produced by solar flares, and can be used to infer properties of the accelerated electrons and magnetic field of the flaring region. This microwave emission is highly dependent on many local plasma parameters, and the viewing angle. To correctly interpret observations, detailed simulations of the emission are required. Additionally, gyrosynchrotron emission from the chromosphere has been largely ignored in modelling efforts, and recent studies have shown the importance of thermal emission at millimetric wavelengths. Thyr is a new tool for modelling microwave emission from three-dimensional flaring loops with spatially varying atmosphere and increased resolution in the lower corona and chromosphere. Thyr is modular and open-source, consisting of separate components to compute the thermal and non-thermal microwave emission coefficients and perform three-dimensional radiative transfer (in local thermodynamic equilibrium). The radiative transfer integral is computed by a novel ray-marching technique to efficiently compute the contribution of many volume elements. This technique can also be employed on a variety of astrophysics problems. Herein we present a review of the theory of gyrosynchrotron radiation, and two simulations of identical flare loops in low- and high-resolution performed with Thyr, with a spectral imaging analysis of differing regions. The high-resolution simulation presents a spectral hardening at higher frequencies. This hardening originates around the top of the chromosphere due to the strong convergence of the magnetic field, and is not present in previous models due to insufficient resolution. This hardening could be observed with a coordinated flare observation from active radio observatories.

Accepted for publication in MNRAS

References in corpus (8)

• Soft X-ray Pulsations in Solar Flares
• 3D Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity
• Formation of the thermal infrared continuum in solar flares
• On the nature of off-limb flare continuum sources detected by SDO/HMI
• Three-dimensional Forward-fit Modeling of the Hard X-Ray and the Microwave Emissions of the 2015 June 22 M6.5 Flare
• Coronal Magnetography of a Simulated Solar Active Region from Microwave Imaging Spectropolarimetry
• ALMA Discovery of Solar Umbral Brightness Enhancement at λ=3 mm
• Solar ALMA: Observation-Based Simulations of the mm and sub-mm Emissions from Active Regions