Determining the acceleration regions of in situ electrons using remote radio and X-ray observations

TL;DR

This study combines remote radio and X-ray observations with in situ data to identify the acceleration regions of solar energetic electrons, revealing their origin, escape paths, and connection to solar shock and flare processes.

Contribution

It introduces a method integrating remote sensing and in situ data with 3D modeling to pinpoint electron acceleration sites and mechanisms in solar events.

Findings

Type II radio burst linked to electron acceleration site.

In situ electrons associated with shock acceleration.

Different radio bursts connected to separate magnetic field lines.

Abstract

Solar energetic particles in the heliosphere are produced by flaring processes on the Sun or shocks driven by coronal mass ejections. These particles are regularly detected remotely as electromagnetic radiation (X-rays or radio emission), which they generate through various processes, or in situ by spacecraft monitoring the Sun and the heliosphere. We aim to combine remote-sensing and in situ observations of energetic electrons to determine the origin and acceleration mechanism of these particles. Here, we investigate the acceleration location, escape, and propagation directions of electron beams producing radio bursts observed with the Low Frequency Array (LOFAR), hard X-ray (HXR) emission and, in situ electrons observed at Solar Orbiter (SolO) on 3 October 2023. These observations are combined with a three-dimensional (3D) representation of the electron acceleration locations and results from a magneto-hydrodynamic (MHD) model of the solar corona in order to investigate the origin and connectivity of electrons observed remotely at the Sun to in situ electrons. We observed a type II radio burst with good connectivity to SolO, where a significant electron event was detected. However, type III radio bursts and Hard X-rays were also observed co-temporally with the elctron event but likely connected to SolO by different far-sided field lines. The injection times of the SolO electrons are simultaneous with both the onset of the type II radio burst, the group of type III bursts and the presence of a second HXR peak, however, the most direct connection to SolO is that of the type II burst location. The in situ electron spectra point to shock acceleration of electrons with a short-term connection to the source region.