Letter to the Editor

Suprathermal particles from corotating interaction regions during the first perihelion pass of Solar Orbiter

¹ Johns Hopkins Applied Physics Lab., Laurel, MD 20723, USA
e-mail: Robert.Allen@jhuapl.edu
² Space Research Group, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
³ Institut für Experimentelle und Angewande Physik, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
⁴ Now at DSI Datensicherheit GmbH, Rodendamm 34, 28816 Stuhr, Germany
⁵ Now at Deutsches Elektronen-Synchrotron (DESY), Platanenallee 6, 15738 Zeuthen, Germany
⁶ Now at German Aerospace Center (DLR), Department of Extrasolar Planets and Atmospheres, Berlin, Germany
⁷ Now at Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
⁸ Now at Univ. Colorado/LASP, Boulder, CO, USA

Received: 6 November 2020
Accepted: 20 December 2020

Abstract

The first orbit of Solar Orbiter provided comprehensive measurements of six corotating interaction regions (CIRs) within 1 au. Five of these CIRs were also observed by ACE at 1 au, allowing for comparisons of the suprathermal ion intensities and spectra at different radial distances. Only subtle modulations of the ⁴He spectral slopes are observed between Solar Orbiter and ACE. Additionally, the radial gradients of 226−320 keV/nuc ⁴He ion intensities between Solar Orbiter and ACE are similar to that of 1.53 MeV H reported by Van Hollebeke et al. (1978, J. Geophys. Res., 83, A10). These observations provide a new addition to the study of the radial dependence of CIR-associated suprathermal ions in the inner heliosphere.