Propagation of Solar Energetic Particles during Multiple Coronal Mass Ejection Events

TL;DR

This study investigates how multiple coronal mass ejections influence the propagation and detection of solar energetic particles, revealing that earlier CMEs can hinder SEP detection by altering particle acceleration or propagation paths.

Contribution

It provides new insights into the effects of sequential CMEs on SEP propagation and explains the absence of SEP events during certain solar eruptions.

Findings

Earlier CMEs reduce seed particle populations affecting acceleration.

Type III radio bursts are halted at higher frequencies in later events.

Sequential CMEs can prevent SEP detection near Earth.

Abstract

We study solar energetic particle (SEP) events during multiple solar eruptions. The analysed sequences, on 24-26 November 2000, 9-13 April 2001, and 22-25 August 2005, consisted of halo-type coronal mass ejections (CMEs) that originated from the same active region and were associated with intense flares, EUV waves, and interplanetary (IP) radio type II and type III bursts. The first two solar events in each of these sequences showed SEP enhancements near Earth, but the third in the row did not. We observed that in these latter events the type III radio bursts were stopped at much higher frequencies than in the earlier events, indicating that the bursts did not reach the typical plasma density levels near Earth. To explain the missing third SEP event in each sequence, we suggest that the earlier-launched CMEs and the CME-driven shocks either reduced the seed particle population and thus led to inefficient particle acceleration, or that the earlier-launched CMEs and shocks changed the propagation paths or prevented the propagation of both the electron beams and SEPs, so that they did not get detected near Earth even when the shock arrivals were recorded.