Parametric simulation studies on the wave propagation of solar radio emission: the source size, duration, and position

Abstract

The observed features of the radio sources indicate complex propagation effects embedded in the waves of solar radio bursts. In this work, we perform ray-tracing simulations on radio wave transport in the corona and interplanetary region with anisotropic electron density fluctuations. For the first time, the variation of the apparent source size, burst duration, and source position of both fundamental emission and harmonic emission at frequency 35 MHz are simulated as the function of the anisotropic parameter $\alpha$ and the angular scattering rate coefficient $\eta ={\epsilon }^2/h_0$, where ${\epsilon }^2=⟨\delta n^2⟩/n^2$ is the density fluctuation level and $h_0$ is its correlation length near the wave exciting site. It is found that isotropic fluctuations produce a much larger decay time than a highly anisotropic fluctuation for fundamental emission. By comparing the observed duration and source size with the simulation results in the parameter space, we can estimate the scattering coefficient and the anisotropy parameter $\eta =8.9\times 10^{-5}\mathrm{k}{\mathrm{m}}^{-1}$ and $\alpha =0.719$ with point pulse source assumption. Position offsets due to wave scattering and refraction can produce the co-spatial of fundamental and harmonic waves in observations of some type III radio bursts. The visual speed due to the wave propagation effect can reach 1.5\,$c$ for $\eta =2.4\times 10^{-4}\mathrm{k}{\mathrm{m}}^{-1}$ and $\alpha =0.2$ for fundamental emission in the sky plane, accompanying with large expansion rate of the source size. The visual speed direction is mostly identical to the offset direction, thus, for the observation aiming at obtaining the source position, the source centroid at the starting point is closer to the wave excitation point.

19 pages

References in corpus (8)

• Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe
• Magnetic Reconnection During the Post-Impulsive Phase of a Long-Duration Solar Flare: Bi-Directional Outflows as a Cause of Microwave and X-ray Bursts
• Large scale simulations of solar type III radio bursts: flux density, drift rate, duration and bandwidth
• A solar type II radio burst from CME-coronal ray interaction: simultaneous radio and EUV imaging
• Radio Echo in the Turbulent Corona and Simulations of Solar Drift-Pair Radio Bursts
• Interferometric Imaging with LOFAR Remote Baselines of the Fine Structures of a Solar Type IIIb Radio Burst
• A Fokker-Planck Framework for Studying the Diffusion of Radio Burst Waves in the Solar Corona
• First imaging spectroscopy observations of solar drift pair bursts

Cited by in corpus (10)

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• Multi-wavelength Observations of a Metric Type-II Event
• Quantifying the Magnetic Structure of a Coronal Shock Producing a Type II Radio Burst
• Interferometric imaging of the type IIIb and U radio bursts observed with LOFAR on 22 August 2017
• The frequency ratio and time delay of solar radio emissions with fundamental and harmonic components
• Imaging and spectropolarimetric observations of a band-split type II solar radio burst with LOFAR
• Observation and Modeling of Small Spatial Structures of Solar Radio Noise Storms using the uGMRT
• Solar Radio-Frequency Reflectivity and Localization of FRB from Solar Reflection