Analysis of type II and type III radio bursts associated with SEPs from non-interacting/interacting radio-loud CMEs

TL;DR

This study compares radio burst properties and SEP event characteristics between interacting and non-interacting CMEs, revealing correlations and differences in radio emissions, CME speeds, and SEP intensities, with implications for space weather prediction.

Contribution

It provides a comprehensive comparison of radio burst features and SEP associations for interacting versus non-interacting CMEs, highlighting key differences and correlations.

Findings

High correlation between type II burst drift rates and frequencies for both CME types.

CME speed correlates with DH type II burst drift rates in non-interacting events.

SEP peak intensities are four times higher in interacting CME events for western sources.

Abstract

We analyze radio bursts observed in events with interacting/non-interacting CMEs that produced major SEPs (Ip $>$ 10 MeV) fromApril 1997 to December 2014.We compare properties of meter (m), deca-hectometer (DH) type II as well as DH type III bursts, and time lags for interacting-CME-associated (IC) events and non-interacting-CME-associated (NIC) events. About 70\% of radio emissions were observed in events of both types from meters to kilometers. We found high correlations between the drift rates and mid-frequencies of type II radio bursts calculated as the mean geometric between their starting and ending frequencies for both NIC and IC-associated events (Correlation coefficient \textit{R}$^{2}$ = 0.98, power-law index $\varepsilon$ = 1.68 $\pm $ 0.16 and \textit{R}$^{2}$ = 0.93, $\varepsilon$ = 1.64 $\pm $ 0.19 respectively).We also found a correlation between the frequency drift rates of DH type II bursts and space speeds of CMEs in NIC-associated events. The absence of such correlation for IC-associated events confirms that the shock speeds changed in CME--CME interactions. For the events with western source locations, the mean peak intensity of SEPs in IC-associated events is four times larger than that in NIC-associated SEP events. From the mean time lags between the start times of SEP events and the start of m, DH type II, and DH type III radio bursts, we inferred that particle enhancements in NIC-associated SEP events occurred earlier than in IC-associated SEP events. The difference between NIC events and IC events in the mean values of parameters of type II and type III bursts is statistically insignificant.