Solar Type IV bursts at frequencies 10-30 MHz

TL;DR

This study presents the first detailed observations of Solar Type IV radio bursts at 10-30 MHz, revealing their complex structures, drift rates, and durations, using high-sensitivity radio telescopes over a three-year period.

Contribution

It provides new insights into the properties and fine structures of Type IV bursts at low frequencies, including their drift rates and zebra structures, based on extensive observational data.

Findings

Type IV bursts have fluxes of 10-2000 s.f.u. at maximum.

Durations of bursts are about 1-2 hours or more.

Sub-bursts exhibit drift rates of 1-2 MHz/s, with some showing zebra structures.

Abstract

The results of the first observations of Type IV bursts at frequencies 10-30 MHz are presented. These observations were carried out at radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) during the period 2003-2006. Detection of Type IV bursts in wide band from 10 to 30MHz with high sensitivity and time resolution allowed to study their properties in details. These bursts have fluxes 10-2000s.f.u. at maximum phase. Their durations are about 1-2 hours and even more. Some of Type IV bursts drift from high to low frequencies with drift rates about 10kHz/s. All observed Type IV bursts have fine structures in the form of sub-bursts with durations from 2s to 20s and frequency drift rates in a majority of 1-2MHz/s. In most cases, sub-bursts with negative drift rates were registered. Sometimes sub-bursts in absorption with durations 10-200s against Type IV burst background have been observed. The Type IV burst observed on July 22, 2004 had zebra structure, in which single zebra stripes had positive, negative and infinite drift rates.