DH type II radio bursts during solar cycles 23-25: Origin and association with solar eruptive events

TL;DR

This study analyzes the occurrence, classification, and associations of DH type II solar radio bursts across solar cycles 23-25, revealing variations in activity patterns and links to solar eruptive events.

Contribution

It provides a comprehensive classification of DH type II bursts based on end-frequency and explores their association with CMEs and flares over three solar cycles.

Findings

HFG category is most common (~47%)

LFG events are linked to fast CMEs and X-class flares

Significant temporal shifts in activity peaks across cycles

Abstract

We analyses occurrence of DH type II solar radio bursts spanning over solar cycles 23-25 during which a total of 590 DH type II bursts are reported with confirmed 568 and 462 cases of associated CME and flares, respectively. We find short-term yet important differences in DH type II activity when the data is examined in terms of event counts and their durations, e.g., temporal shift in the peak activity during cycle 24 and variation in the growth rate of the activity level during cycle 25. For an in-depth exploration, DH type II bursts are classified in 3 categories based on their end-frequencies: Low-, Medium-, and High- Frequency Groups (LFG, MFG, and HFG, respectively). The HFG category is the most populous (~47 %) while the LFG category occupy about a quarter of the events (~24 %). The LFG events show a clear inclination toward fastest CMEs and X-class flares with a quarter of events exhibiting end frequency below 50 MHz.