Comparing the Properties of ICME-Induced Forbush Decreases at Earth and Mars
arXiv:2003.03157 · doi:10.1029/2019JA027662
Abstract
Forbush decreases (FDs), which are short-term drops in the flux of galactic cosmic rays, are caused by the shielding from strong and/or turbulent magnetic structures in the solar wind, especially interplanetary coronal mass ejections (ICMEs) and their associated shocks, as well as corotating interaction regions. Such events can be observed at Earth, for example, using neutron monitors, and also at many other locations in the solar system, such as on the surface of Mars with the Radiation Assessment Detector instrument onboard Mars Science Laboratory. They are often used as a proxy for detecting the arrival of ICMEs or corotating interaction regions, especially when sufficient in situ solar wind measurements are not available. We compare the properties of FDs observed at Earth and Mars, focusing on events produced by ICMEs. We find that FDs at both locations show a correlation between their total amplitude and the maximum hourly decrease, but with different proportionality factors. We explain this difference using theoretical modeling approaches and suggest that it is related to the size increase of ICMEs, and in particular their sheath regions, en route from Earth to Mars. From the FD data, we can derive the sheath broadening factor to be between about 1.5 and 1.9, agreeing with our theoretical considerations. This factor is also in line with previous measurements of the sheath evolution closer to the Sun.
References in corpus (18)
- Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars
- On Sun-to-Earth Propagation of Coronal Mass Ejections
- Interactions between Coronal Mass Ejections Viewed in Coordinated Imaging and In Situ Observations
- Global and local expansion of magnetic clouds in the inner heliosphere
- Modeling the evolution and propagation of the 2017 September 9th and 10th CMEs and SEPs arriving at Mars constrained by remote-sensing and in-situ measurement
- Superposed epoch study of ICME sub-structures near Earth and their effects on galactic cosmic rays
- Generic magnetic field intensity profiles of interplanetary coronal mass ejections at Mercury, Venus and Earth from superposed epoch analyses
- Dynamical evolution of a magnetic cloud from the Sun to 5.4 AU
- Plasma Depletion and Mirror Waves Ahead of Interplanetary Coronal Mass Ejections
- The Lunar Lander Neutron and Dosimetry (LND) Experiment on Chang'E 4
- An Analytical Diffusion-Expansion Model for Forbush Decreases Caused by Flux Ropes
- Dependence of the Martian radiation environment on atmospheric depth: Modeling and measurement
- A generalized approach to model the spectra and radiation dose rate of solar particle events on the surface of Mars
- Measurements of Forbush decreases at Mars: both by MSL on ground and by MAVEN in orbit
- Unusual plasma and particle signatures at Mars and STEREO-A related to CME-CME interaction
- Ready functions for calculating the Martian radiation environment
- Quantifying the Propagation of Fast Coronal Mass Ejections from the Sun to Interplanetary Space Combining Remote Sensing and Multi-Point in-situ Observations
- Tracking and Validating ICMEs Propagating Toward Mars Using STEREO Heliospheric Imagers Combined With Forbush Decreases Detected by MSL/RAD
Cited by in corpus (7)
- Evolution of coronal mass ejections and the corresponding Forbush decreases: modelling vs multi-spacecraft observations
- Radial Evolution of the April 2020 Stealth Coronal Mass Ejection between 0.8 and 1 AU -- A Comparison of Forbush Decreases at Solar Orbiter and Earth
- New insights from cross-correlation studies between solar activity indices and cosmic-ray flux during Forbush decrease events
- Characterizing ICME-related Forbush Decreases at Mercury using MESSENGER Observations: Identification of a One or Two-Step Structure
- Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space: Need for contextual energetic particle measurements at Earth and supporting distributed observations
- The two-step Forbush decrease: a tale of two substructures modulating galactic cosmic rays within coronal mass ejections
- Magnetic Structure and Propagation of Two Interacting CMEs from the Sun to Saturn