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Free keywords:
Physics, Space Physics, physics.space-ph, Astrophysics, Earth and Planetary Astrophysics, astro-ph.EP, Astrophysics, Solar and Stellar Astrophysics, astro-ph.SR
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.
