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Spatio-Temporal Evolution of the March 2022 ICME Revealed by Multi-Point Observations of Forbush Decreases

Gaku Kinoshita, Beatriz Sanchez-Cano, Yoshizumi Miyoshi, Laura Rodriguez-Garcia, Emilia Kilpua, Benoit Lavraud, Mathias Rojo, Marco Pinto, Yuki Harada, Go Murakami, Yoshifumi Saito, Shoichiro Yokota, Daniel Heyner, David Fischer, Nicolas Andre, Kazuo Yoshioka

TL;DR

This paper tackles the challenge of linking interplanetary coronal mass ejections (ICMEs) to Forbush Decreases (FDs) by performing a multi-point analysis of a March 2022 ICME using Solar Orbiter, BepiColombo, and near-Earth spacecraft. By combining in situ magnetic field and plasma data with GCR measurements across different heliocentric distances and longitudes, the authors show that FD depth and gradient diminish as ICMEs expand radially, and that longitudinal shielding of galactic cosmic rays is anisotropic, leading to variable FD responses at different spacecraft along the same ICME. The study also reveals that interactions with ambient CIRs and subsequent ICMEs can modify FD profiles, sometimes transforming a two-step FD into a single-step event, depending on observer geometry and magnetic-field structure. Overall, the work provides a practical framework for multi-point FD comparisons and highlights the necessity of coupling FD observations with detailed ICME substructure mapping for inner-heliosphere studies.

Abstract

Interplanetary coronal mass ejections (ICMEs) cause Forbush Decreases (FDs) effects, which are local decreases in background galactic cosmic rays (GCR). Even though FDs can be observed with simple particle instruments, their amplitude and shape provide physical profiles of passing ICMEs. However, in some cases, previous statistical studies of the heliocentric distance dependence of FD changes associated with ICME propagation have found no strong correlation. We need the criteria for evaluating the relationship between ICMEs structure and FD, necessary for FDs statistical analysis. This study investigates the effect of evolutions and interactions of ICMEs on FDs profiles in the inner Solar System, using multipoint comparisons. We focus on multipoint ICME observations by Solar Orbiter, BepiColombo, and near-Earth spacecraft from March 10-16, 2022, when these spacecraft were ideally located for studying the radial and longitudinal evolutions of ICME and accompanying FDs. We compared GCR variations with the multiple in-situ data and ICME model, clarifying the correspondence between the evolution of each ICME structure in radial and azimuthal directions and the depth and gradients of the FD. The radial comparison revealed decreases in FD intensities and gradients associated with the expansion of the ICME. The longitudinal difference found in FD intensity indicates longitudinal variations of the ICMEs shielding effect. These results suggest that accurate multi-point FD comparisons require determining the relationship between the observers position and the inner structure of the passing ICMEs.

Spatio-Temporal Evolution of the March 2022 ICME Revealed by Multi-Point Observations of Forbush Decreases

TL;DR

This paper tackles the challenge of linking interplanetary coronal mass ejections (ICMEs) to Forbush Decreases (FDs) by performing a multi-point analysis of a March 2022 ICME using Solar Orbiter, BepiColombo, and near-Earth spacecraft. By combining in situ magnetic field and plasma data with GCR measurements across different heliocentric distances and longitudes, the authors show that FD depth and gradient diminish as ICMEs expand radially, and that longitudinal shielding of galactic cosmic rays is anisotropic, leading to variable FD responses at different spacecraft along the same ICME. The study also reveals that interactions with ambient CIRs and subsequent ICMEs can modify FD profiles, sometimes transforming a two-step FD into a single-step event, depending on observer geometry and magnetic-field structure. Overall, the work provides a practical framework for multi-point FD comparisons and highlights the necessity of coupling FD observations with detailed ICME substructure mapping for inner-heliosphere studies.

Abstract

Interplanetary coronal mass ejections (ICMEs) cause Forbush Decreases (FDs) effects, which are local decreases in background galactic cosmic rays (GCR). Even though FDs can be observed with simple particle instruments, their amplitude and shape provide physical profiles of passing ICMEs. However, in some cases, previous statistical studies of the heliocentric distance dependence of FD changes associated with ICME propagation have found no strong correlation. We need the criteria for evaluating the relationship between ICMEs structure and FD, necessary for FDs statistical analysis. This study investigates the effect of evolutions and interactions of ICMEs on FDs profiles in the inner Solar System, using multipoint comparisons. We focus on multipoint ICME observations by Solar Orbiter, BepiColombo, and near-Earth spacecraft from March 10-16, 2022, when these spacecraft were ideally located for studying the radial and longitudinal evolutions of ICME and accompanying FDs. We compared GCR variations with the multiple in-situ data and ICME model, clarifying the correspondence between the evolution of each ICME structure in radial and azimuthal directions and the depth and gradients of the FD. The radial comparison revealed decreases in FD intensities and gradients associated with the expansion of the ICME. The longitudinal difference found in FD intensity indicates longitudinal variations of the ICMEs shielding effect. These results suggest that accurate multi-point FD comparisons require determining the relationship between the observers position and the inner structure of the passing ICMEs.
Paper Structure (16 sections, 11 figures, 2 tables)

This paper contains 16 sections, 11 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The ICME event in 2022/3
  3. Data Sources
  4. Solar orbiter
  5. Near Earth spacecraft
  6. BepiColombo
  7. In Situ Observations
  8. Solar Orbiter
  9. Near-Earth spacecraft
  10. BepiColombo
  11. Discussion
  12. The radial comparison (Solar Orbiter and near Earth spacecraft)
  13. The radial decrease in FDs' step number
  14. Internal structural changes in the sheath and their effects on FDs, as inferred from comparisons in the radial direction
  15. The Longitudinal comparison (Solar Orbiter and BepiColombo)
  16. ...and 1 more sections

Figures (11)

  • Figure 1: (a) STEREO-A SECCI/COR2 white-light image taken on 2022/3/10 at 19:23 UT (b) SDO AIA image taken on 2022/3/10 at 19:23 UT with 193 Å, (c) GOES X-ray flux 1-minute data. These figures are created with SunPy software sunpy_community2020
  • Figure 2: Simulations in the WSA-Enlil + Cone model for the ICME in 2022/3/12-3/13. The ICME simulations are adapted from the Space Weather Database Of Notifications, Knowledge, Information (DONKI). https://kauai.ccmc.gsfc.nasa.gov/DONKI/view/WSA-ENLIL/19410/1
  • Figure 3: (a) IGRF-13 magnetic field distribution model and the orbit of LRO in the X-Y plane of J2000 coordinate system, (b) The $B_{total}$ variations of LRO's orbit (IGRF-13) and changes of lamor radius of a 100 MeV proton. $R_E$ represents the Earth's radius.
  • Figure 4: FD detected by CRaTER in March 2022 and lunar altitude variations of LRO
  • Figure 5: The response functions of MMO/SPM. $10^6$ protons are tested for each primary energy to derive g-factors. These response functions are derived based on the shielding effects around the MMO by the MOSIF, the MPO, and the MTM, so please note that they are only valid for events detected during the cruise phase.
  • ...and 6 more figures