Speaker
Description
Type II solar radio bursts are believed to be caused by magnetohydrodynamics (MHD) shock-accelerated electrons in the solar corona. Often type IIs exhibit fine structures in their dynamic spectra. For example, both fundamental and harmonic bands of type II bursts are split into two sub-bands. This is generally believed to be coming from upstream and downstream regions of the shock; however, this explanation remains unconfirmed. Here we present results from imaging analysis of type II radio burst band-splitting and fine structures observed by the Murchison Widefield Array (MWA) on 2014-Sep-28. The MWA provides high-sensitivity imaging spectroscopy in the range of 80-300 MHz with a time resolution of 0.5 s and a frequency resolution of 40 kHz. Our analysis provides rare evidence that band-splitting is caused by emission from multiple parts of the shock (as opposed to the upstream/downstream hypothesis). We also examine the small-scale motion of type II fine structure radio sources in MWA images. We suggest that this small-scale motion may arise due to propagation effects from coronal turbulence, and not because of the physical motion of the shock location. The study of the systematic and small-scale motion of fine structures may therefore provide a measure of turbulence in different regions of the shock and corona.
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