# Forbush decreases and $<$ 2-day GCR flux non-recurrent variations studied with LISA Pathfinder

## TL;DR

This study analyzes short-term non-recurrent galactic cosmic-ray flux variations observed by LISA Pathfinder at L1, focusing on Forbush decreases and their relation to interplanetary structures, providing insights into space weather effects on cosmic rays.

## Contribution

It presents the first detailed analysis of GCR flux variations and Forbush decreases observed by LISA Pathfinder, linking these to interplanetary phenomena and comparing with other space-based observations.

## Key findings

- Most peaks caused by plasma compression regions between high-speed streams.
- Depressions mainly associated with heliospheric current sheet crossings.
- GCR flux parameterization applies across different event intensities.

## Abstract

Non-recurrent short term variations of the galactic cosmic-ray (GCR) flux above 70 MeV n$^{-1}$ were observed between 2016 February 18 and 2017 July 3 aboard the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5$\times$10$^6$ km from Earth. The energy dependence of three Forbush decreases (FDs) is studied and reported here. A comparison of these observations with others carried out in space down to the energy of a few tens of MeV n$^{-1}$ shows that the same GCR flux parameterization applies to events of different intensity during the main phase. FD observations in L1 with LPF and geomagnetic storm occurrence is also presented. Finally, the characteristics of GCR flux non-recurrent variations (peaks and depressions) of duration $<$ 2 days and their association with interplanetary structures are investigated. It is found that, most likely, plasma compression regions between subsequent corotating high-speed streams cause peaks, while heliospheric current sheet crossing cause the majority of the depressions.