Radial evolution of interplanetary coronal mass ejection-associated particle acceleration observed by Solar Orbiter and ACE

¹ Johns Hopkins University, Baltimore, MD, USA 21218
² Southwest Research Institute, San Antonio, TX, USA 78238
³ General Linear Space Plasma Lab LLC, Foster City, CA 94404, USA
⁴ Johns Hopkins Applied Physics Laboratory, Laurel, MD 20723-6099, USA
⁵ University of Alcalá, Alcalá de Henares, Madrid, Spain
⁶ University of Kiel, Kiel, Germany

^⋆ Corresponding author; mwalke85@jhu.edu

Received: 10 May 2024
Accepted: 19 October 2024

Abstract

On 2022 March 10 a coronal mass ejection erupted from the Sun, resulting in Solar Orbiter observations at 0.45 au of both dispersive solar energetic particles arriving prior to the interplanetary coronal mass ejection (ICME) and locally accelerated particles near the ICME-associated shock structure as it passed the spacecraft on 2022 March 11. This interplanetary shock was later detected on 2022 March 14 by the Advanced Composition Explorer (ACE), which was radially aligned with Solar Orbiter, at 1 au. Ion composition data from both spacecraft – via the Solar Orbiter Energetic Particle Detector/ Suprathermal Ion Spectrograph (EPD/SIS) and the Ultra Low Energy Isotope Spectrometer (ULEIS) on ACE – allowed for an in-depth analysis of the radial evolution of species-dependent ICME-driven shock-associated acceleration processes for this event. We present a study of the ion spectra observed at 0.45 and 1 au during both the gradual solar energetic particle and energetic storm particle phases of the event. The shapes of the spectra seen at each spacecraft differ significantly, likely due to the varying shock geometry: Solar Orbiter spectra tend to lack spectral breaks, and the higher-energy portions of the ACE spectra have a comparable average flux to the Solar Orbiter spectra. Through an analysis of rigidity effects on the spectral breaks observed by ACE, we conclude that the 1 au observations were largely influenced by a suprathermal pool of He⁺ ions that were enhanced due to propagation along a stream interaction region that was interacting with the ICME at the times of observation.