Corotating Interaction Regions as Measured with Solar Orbiter and ACE

Abstract:

Solar Orbiter, a joint ESA/NASA mission, is designed to study the Sun and inner heliosphere in greater detail than ever before. After it was launched on February 9, 2020 at Cape Canaveral Florida, the spacecraft reached its first perhelion at 0.5 AU on June 15, 2020. Perihelion passes at distances close to the Sun provide direct observations of the in-situ environment in the inner heliosphere. Understanding the physical processes operating on acceleration and transport of suprathermal and energetic particle is a major goal of the SolarOrbiter mission because of the importance of acceleration processes in solar system and astrophysical sites, and because of the potential impact of these events on space hardware. During minimum solar activity, the heliospheric environment is dominated by stream and corotating interaction regions (CIRs). In this paper, we report results from the Solar Orbiter Energetic Particle Detector/Suprathermal Ion Spectrograph (EPD/SIS) which measures suprathermal ion composition from 10s keV/nucleon to ~10s of MeV/nucleon. Since the instrument was fully commissioned in April, 2020, we measured a series of CIRs and many of these events were also measured by ACE at 1 AU. Direct comparison of these events allows us to examine the transport and acceleration of the CIR-associated suprathermal particles between 1 au and 0.5 au.