TY  - JOUR
A1  - Freiherr von Forstner, Johan L.
A1  - Guo, Jingnan
A1  - Wimmer-Schweingruber, Robert F.
A1  - Dumbovic, Mateja
A1  - Janvier, Miho
A1  - Démoulin, Pascal
A1  - Veronig, Astrid
A1  - Temmer, Manuela
A1  - Papaioannou, Athanasios
A1  - Dasso, Sergio
A1  - Hassler, Donald M.
A1  - Zeitlin, Cary J.
T1  - Comparing the Properties of ICME-Induced Forbush Decreases at Earth and Mars
Y1  - 2020
VL  - 125
IS  - 3
JF  - Journal of Geophysical Research: Space Physics
DO  - 10.1029/2019JA027662
DO  - 10.23689/fidgeo-5001
N2  - 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.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/9347
ER  -