Observation and analysis of the anisotropic Forbush decrease of 24 March 2024

Abstract

It is known that GCR flux exhibits notable transient suppressions due to coronal mass ejections (CMEs) and co-rotating interaction regions (CIRs) in the solar wind, called Forbush decreases (FDs). FDs are observed as fast, occasionally two-step, decreases in the count rate of particle counters. The decrease is usually followed by a gradual recovery taking up to several days or even a week. A particularly strong FD, observed as suppression of the flux of galactic cosmic rays was observed by the global network of ground-based neutron monitors (NMs) on 24–25 March 2024. The decrease revealed an unusual rapid recovery leading to false ground-level enhancement alarm from the cosmic radiation warning systems. The event was highly anisotropic, with anisotropy focused nearly on the anti-sunward direction. Here we present the observations, focusing on NM records, and the corresponding analysis.