The largest Forbush decrease in 20 years: Preliminary analysis of SEVAN network observations

TL;DR

This paper analyzes the largest Forbush Decrease in 20 years observed during solar cycle 25, using SEVAN network data to study cosmic ray variations caused by consecutive CMEs and their complex effects.

Contribution

It provides the first detailed analysis of a major FD event in solar cycle 25 using SEVAN data, revealing anisotropies and temporal structures across the network.

Findings

Two distinct FD minima observed with prolonged recovery.

Significant anisotropies in cosmic ray response across detectors.

Correlation of FD phases with interplanetary shock signatures.

Abstract

We present a preliminary analysis of the largest Forbush Decrease (FD) observed in solar cycle 25 using SEVAN network data. Triggered by consecutive Earth-directed CMEs on May 30 and 31, 2025, this event produced two distinct FD minima and a prolonged recovery, with significant anisotropies in cosmic ray response across the network. The timing of interplanetary shock arrivals was confirmed by SSC signatures at 05:22 UTC on June 1 and 10:19 UTC on June 2, marking the onset of each FD phase. The depth and temporal structure of the FD varied across SEVAN detectors, providing insights into the complex heliospheric and magnetospheric dynamics during this multi-CME event.