- 1Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Japan (g-kinoshita20686@g.ecc.u-tokyo.ac.jp)
- 2Japan Aerospace Exploration Agency (JAXA), Japan
- 3European Space Research and Technology Centre, European Space Agency, Netherlands
- 4Department of Complexity Science and Engineering, Graduate School of Frontier Science, The University of Tokyo, Japan
- 5Institute for Space‐Earth Environmental Research, Nagoya University, Japan
Direct observations in the inner heliosphere have been limited due to the large gravitational potential differences, leaving many aspects of the physical processes governing the propagation of interplanetary coronal mass ejections (ICMEs) and solar energetic particles (SEPs) unresolved. Recent multi-point observations by spacecraft such as BepiColombo (Benkhoff et al., 2021; Murakami et al., 2020), Parker Solar probe (Fox et al., 2016) and Solar Orbiter (Müller et al., 2020) offer unique opportunities to explore the radial and longitudinal evolution of solar ejecta in unprecedented detail (e.g. Hadid et al., 2021; Mangano et al., 2021).
In this study, we utilized the Solar Particle Monitor (SPM) aboard BepiColombo/Mio, a non-scientific housekeeping radiation monitor for scientific observations. SPM’s ability to measure higher energetic particles makes it particularly effective for studying phenomena such as SEPs and galactic cosmic rays. We developed a novel inversion method based on response functions derived from Geant4 (Allison et al., 2016) radiation simulations, and reconstructed the primary energy and flux of incident particles from SPM data (Kinoshita et al., 2025, JGR).
This method was applied to an SEP event observed in March 2022, when BepiColombo and STEREO-A were aligned along the same Parker spiral magnetic field line. The energy spectra from BepiColombo/SPM, BERM (Pinto et al., 2022) and STEREO-A/HET (Von Rosenvinge et al., 2008) showed remarkable similarity, suggesting a common origin. Additionally, SPM detected a Forbush Decrease (FD) event following the SEP, marking the arrival of an ICME. This ICME also reached Earth, where FD signatures were recorded by ground neutron monitors. A comparison of FD profiles such as shapes and depth between BepiColombo and the Earth provided insights into the spatio-temporal evolution of the ICME as it propagated in the inner heliosphere.
Our findings contribute to a deeper understanding of SEP acceleration mechanisms and ICME dynamics in the inner heliosphere. Moreover, they demonstrate the potential of repurposing housekeeping instruments for scientific applications, paving the way for expanding solar observation networks with ongoing and future missions.
How to cite: Kinoshita, G., Ueno, H., Murakami, G., Pinto, M., Yoshioka, K., Miyoshi, Y., and Saito, Y.: Unveiling SEP Acceleration and ICME Evolution in the Inner Heliosphere using Housekeeping Radiation Data Acquired by BepiColombo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4776, https://doi.org/10.5194/egusphere-egu25-4776, 2025.
