Decameter Type IV Burst Associated with a behind-the-limb CME Observed on 7 November 2013

TL;DR

This study analyzes a decameter Type IV solar radio burst linked to a behind-the-limb CME, revealing its source, propagation, and associated shock dynamics through multi-instrument observations.

Contribution

It identifies the origin of the Type IV burst as the CME core's periphery and demonstrates how the burst's frequency drift relates to CME expansion, providing new insights into CME-associated radio emissions.

Findings

Type IV burst originates from the CME core periphery at 30 MHz

Radio emission can escape the CME core at 60 MHz

Shock velocities are approximately 1000 km/s and 800 km/s

Abstract

We report on the results of observations of a type IV burst by URAN-2 (Ukrainian Radio interferometer of Academy Scienses) in the frequency range 22 - 33 MHz, which is associated with the CME (coronal mass ejection) initiated by a behind-the-limb active region (N05E151). This burst was observed also by the radio telescope NDA (Nancay Decameter Array) in the frequency band 30 - 60 MHz. The purpose of the article is the determination of the source of this type IV burst. After analysis of the observational data obtained with the URAN-2, NDA, STEREO (Solar-Terrestrial Relations Observatory) A and B spacecraft, and SOHO (Solar and Heliospheric Observatory)spacecraft we come to the conclusion that it is a core of a behind-the-limb CME. We conclude that the radio emission can escape the center of the CME core at a frequency of 60 MHz and originates from the periphery of the core at frequency 30 MHz due to occultation by the solar corona at corresponding frequencies. We find plasma densities in these regions supposing the plasma mechanism of radio emission. We show that the frequency drift of the start of the type IV burst is governed by an expansion of the CME core. Type III bursts, which were observed against this type IV burst, are shown to be generated by fast electrons propagating through the CME core plasma. A type II burst registered at frequencies 44 - 64 MHz and 3 - 16 MHz was radiated by a shock with a velocity of about 1000 km s^{-1} and 800 km s^{-1}, respectively.