Spatial properties of the complex decameter type II burst observed on 31 May 2013

TL;DR

This study analyzes the spatial properties and polarization of a complex type II solar radio burst associated with a narrow Earth-directed CME, revealing detailed source sizes, displacements, and polarization characteristics through interferometric observations.

Contribution

It provides the first detailed spatial and polarization analysis of a complex type II burst associated with a narrow CME using interferometric radio observations.

Findings

Source sizes ranged from 10 to 15 arcmin.

Brightness temperatures reached up to 10^14 K.

Measured source displacements and velocities were model-independent.

Abstract

We present the results of observations of complex powerful type II burst associated with narrow Earth-directed CME, which was ejected at around 11 UT on 31 May 2013. The observations were performed by radio telescope UTR-2, which operated as local interferometer, providing the possibility of detection of the spatial parameters of the radio emission source. There are also polarization data from URAN-2 radio telescope. The CME was detected by two space-born coronagraphs SOHO/LASCO/C2 and STEREO/COR1-BEHIND, and was absolutely invisible for STEREO-AHEAD spacecraft. The associated type II burst consisted of two successive parts of quite different appearance on the dynamic spectrum. The first burst was narrow in frequency, had cloudy structure and was completely unpolarized while the second one represented rich herring-bone structure and exposed high degree of circular polarization. Both parts of the whole event reveal band splitting and well distinguished harmonic structure. The positions and sizes of the sources of the type II burst were found using cross-correlation functions of interferometer bases. The sources of the type II bursts elements were found to be of about 15 arcmin in size in average, with the smallest ones reaching as low as 10 arcmin. Corresponding brightness temperatures were estimated. In most cases these temperatures were between $10^{11}$ and $10^{12}$ K with maximum value as high as $10^{14}$ K. The spatial displacement of the source was measured and model independent velocities of the type II burst sources were determined.