Measuring Forbush decreases and probing CME evolution throughout the heliosphere

Forbush decreases (FDs) are one of the very common in-situ signatures of interplanetary coronal mass ejections (ICMEs) throughout the heliosphere. These short-term reductions in the galactic cosmic ray flux are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). We recently developed an analytical model to explain CME-related FDs using an expansion-diffusion approach and utilized it to develop a best-fit procedure (ForbMod, Dumbovic et al., 2024). According to the model, the amplitude of the depression at a given point in the heliosphere depends on the initial CME properties as well as its evolutionary properties.

We develop a scheme that will allow us to analyze CME evolution using a set of CME-ICME-FD observations, as well as in situ measurements only, and design a graphical user interface to perform ICME and FD analysis throughout the heliosphere. We measure, catalogue and analyse ICMEs and related FDs using Helios, Ulysess, SOHO and Solar Orbiter spacecraft, as well as ground-based measurements from the South Pole neutron monitor at Earth and MSL/RAD at Mars. This research was partly funded by the European Space Agency (projects ForbMod and ForbMod2) and partly by European Union (project SPEARHEAD, No 101135044). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Health and Digital Executive Agency (HaDEA). Neither the European Union nor the granting authority can be held responsible for them.