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

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.

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Cited by in corpus (6)

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• Recurrent galactic cosmic-ray flux modulation in L1 and geomagnetic activity during the declining phase of the solar cycle 24
• Simulating the charging of isolated free-falling masses from TeV to eV energies: detailed comparison with LISA Pathfinder results
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• LISA test-mass charging. Particle flux modeling, Monte Carlo simulations and induced effects on the sensitivity of the observatory
• Diverse properties of electron Forbush decreases revealed by the Dark Matter Particle Explorer