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Sub-second time evolution of Type III solar radio burst sources at fundamental and harmonic frequencies View all abstracts by submitter

Eduard Kontar   Submitted: 2020-10-21 03:44

Recent developments in astronomical radio telescopes opened new opportunities in imaging and spectroscopy of solar radio bursts at sub-second timescales. Imaging in narrow frequency bands has revealed temporal variations in the positions and source sizes that do not fit into the standard picture of type III solar radio bursts, and require a better understanding of radio-wave transport. In this paper, we utilise 3D Monte Carlo ray-tracing simulations that account for the anisotropic density turbulence in the inhomogeneous solar corona to quantitatively explain the image dynamics at the fundamental (near plasma frequency) and harmonic (double) plasma emissions observed at ~ 32~MHz. Comparing the simulations with observations, we find that anisotropic scattering from an instantaneous emission point source can account for the observed time profiles, centroid locations, and source sizes of the fundamental component of type III radio bursts (generated where fpe ≈ 32~MHz). The best agreement with observations is achieved when the ratio of the perpendicular to the parallel component of the wave vector of anisotropic density turbulence is around 0.25. Harmonic emission sources observed at the same frequency (~ 32~MHz, but generated where fpe ≈ 16~MHz) have apparent sizes comparable to those produced by the fundamental emission, but demonstrate a much slower temporal evolution. The simulations of radio-wave propagation make it possible to quantitatively explain the variations of apparent source sizes and positions at sub-second time-scales both for the fundamental and harmonic emissions, and can be used as a diagnostic tool for the plasma turbulence in the upper corona.

Authors: X. Chen, E. P. Kontar, N. Chrysaphi, N. L.S. Jeffrey, M. Gordovskyy, Y. Yan, B. Tan
Projects: LOw Frequency ARray (LOFAR),SDO-AIA

Publication Status: Accepted for publication in ApJ
Last Modified: 2020-10-21 11:17
Go to main E-Print page  The role of small-scale surface motions in the transfer of twist to a solar jet from a remote stable flux rope  Magnetically coupled atmosphere, fast sausage MHD waves, and forced magnetic field reconnection during the SOL2014-09-10T17:45 flare  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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