Trends and Characteristics of High-Frequency Type II Bursts Detected by CALLISTO Spectrometers

TL;DR

This study analyzes high-frequency solar radio type II bursts detected by CALLISTO spectrometers, revealing their origins, association with fast CMEs, and correlation with CME speeds, enhancing understanding of space weather precursors.

Contribution

It provides the first detailed analysis of high-frequency type II bursts' characteristics and their relation to CME properties using multi-instrument observations from 2010 to 2019.

Findings

60% of high-frequency bursts originate from western longitudes.

Strong correlation (0.73) between shock speeds from radio spectra and CME data.

High-frequency bursts are associated with wide, fast CMEs near the solar disk.

Abstract

Solar radio type II bursts serve as early indicators of incoming geo-effective space weather events such as coronal mass ejections (CMEs). In order to investigate the origin of high-frequency type II bursts (HF type II bursts), we have identified 51 of them (among 180 type II bursts from SWPC reports) that are observed by ground-based Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers and whose upper-frequency cutoff (of either fundamental or harmonic emission) lies in between 150 MHz-450 MHz during 2010-2019. We found that 60% of HF type II bursts, whose upper-frequency cutoff $\geq$ 300 MHz originate from the western longitudes. Further, our study finds a good correlation $\sim $ 0.73 between the average shock speed derived from the radio dynamic spectra and the corresponding speed from CME data. Also, we found that analyzed HF type II bursts are associated with wide and fast CMEs located near the solar disk. In addition, we have analyzed the spatio-temporal characteristics of two of these high-frequency type II bursts and compared the derived from radio observations with those derived from multi-spacecraft CME observations from SOHO/LASCO and STEREO coronagraphs.