Characteristics and energy dependence of recurrent galactic cosmic-ray flux depressions and of a forbush decrease with LISA Pathfinder

The final publication is available at IOS Press through http://dx.doi.org/10.3847/1538-4357/aaa774Galactic cosmic-ray (GCR) energy spectra observed in the inner heliosphere are modulated by the solar activity, the solar polarity and structures of solar and interplanetary origin. A high counting rate particle detector (PD) aboard LISA Pathfinder, meant for subsystems diagnostics, was devoted to the measurement of GCR and solar energetic particle integral fluxes above 70 MeV n-1 up to 6500 counts s-1. PD data were gathered with a sampling time of 15 s. Characteristics and energy dependence of GCR flux recurrent depressions and of a Forbush decrease dated 2016 August 2 are reported here. The capability of interplanetary missions, carrying PDs for instrument performance purposes, in monitoring the passage of interplanetary coronal mass ejections is also discussed.Peer ReviewedPreprin

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

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 on board the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5 × 106 km from Earth. The energy dependence of three Forbush decreases 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 are 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 causes the majority of the depressions.Peer ReviewedPostprint (published version

GCR flux 9-day variations with LISA Pathfinder

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Galactic cosmic-ray flux short-term variations and associated interplanetary structures with LISA Pathfinder

The European Space Agency LISA Pathfinder (LPF) mission orbited around the Sun-Earth first Lagrangian point L1 between January 2016 and July 2017. A particle detector aboard LPF allowed for galactic cosmic-ray (GCR) integral flux measurements above 70 MeV n−1 between 2016 February 18 and 2017 July 3 during the descending phase of the present solar cycle N. 24, which is characterized by a positive polarity period. The statistical uncertainty on hourly-averaged GCR countings was of 1%. The characteristics of recurrent and non-recurrent GCR flux short-term variations observed with LPF are reported here. In particular, it is focused on GCR flux variation profiles and their association with the passage of large-scale interplanetary structures. Forbush decrease observations and geomagnetic storm occurrence during LPF are also briefly discussed

GCR flux 9-day variations with LISA Pathfinder

Galactic cosmic-ray (GCR) energy spectra in the heliosphere vary on the basis of the level of solar activity, the status of solar polarity and interplanetary transient magnetic structures of solar origin. A high counting rate particle detector (PD) aboard LISA Pathfinder (LPF) allows for the measurement of galactic cosmic-ray and solar energetic particle (SEP) integral fluxes at energies > 70 MeV n−1 up to 6500 counts s−1. Data are gathered with a sampling time of 15 s. A study of GCR flux depressions associated with the third harmonic of the Sun rotation period (∼ 9 days) is presented here

The CAESAR project for the ASI space weather infrastructure

This paper presents the project Comprehensive spAce wEather Studies for the ASPIS prototype Realization (CAESAR), which aims to tackle the relevant aspects of Space Weather (SWE) science and develop a prototype of the scientific data centre for Space Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather InfraStructure). To this end, CAESAR involves the majority of the SWE Italian community, bringing together 10 Italian institutions as partners, and a total of 92 researchers. The CAESAR approach encompasses the whole chain of phenomena from the Sun to Earth up to planetary environments in a multidisciplinary, comprehensive, and unprecedented way. Detailed and integrated studies are being performed on a number of well-observed “target SWE events”, which exhibit noticeable SWE characteristics from several SWE perspectives. CAESAR investigations synergistically exploit a great variety of different products (datasets, codes, models), both long-standing and novel, that will be made available in the ASPIS prototype: this will consist of a relational database (DB), an interface, and a wiki-like documentation structure. The DB will be accessed through both a Web graphical interface and the ASPIS.py module, i.e., a library of functions in Python, which will be available for download and installation. The ASPIS prototype will unify multiple SWE resources through a flexible and adaptable architecture, and will integrate currently available international SWE assets to foster scientific studies and advance forecasting capabilities

Grad-Shafranov reconstruction of a magnetic cloud: Effects of the magnetic-field topology on the galactic cosmic-ray intensity

The passage of the interplanetary counterpart of a coronal mass ejection was observed at L1 between 2016 August 2 at 14:00 UT and August 3 at 03:00 UT. The transit of shock, sheath and magnetic cloud (MC) regions are identified and the MC configuration is studied through the Grad-Shafranov reconstruction technique. A classical Forbush decrease (FD) in the galactic cosmic ray (GCR) intensity was observed by the particle detector (PD) aboard the European Space Agency LISA Pathfinder (LPF) mission on 2016 August 2. The PD allowed to monitor the GCR intensity at energies above 70 MeV n−1 with a statistical uncertainty of 1% on one-hour binned data. The observed fractional decrease of the GCR intensity around the dip of the event is investigated through a full-orbit particle propagation in the MC and related to the reconstructed magnetic field topology

Interplanetarymedium monitoring with LISA: Lessons from LISA Pathfinder

The Laser Interferometer Space Antenna (LISA) of the European Space Agency (ESA) will be the first low-frequency gravitational-wave observatory orbiting the Sun at 1 AU. The LISA Pathfinder (LPF) mission, aiming at testing the instruments to be located on board the LISA spacecraft (S/C), hosted, among the others, fluxgate magnetometers and a particle detector as parts of a diagnostics subsystem. These instruments allowed us to estimate the magnetic and Coulomb spurious forces acting on the test masses that constitute the mirrors of the interferometer. With these instruments, we also had the possibility to study the galactic cosmic-ray short term-term variations as a function of the particle energy and the associated interplanetary disturbances. Platform magnetometers and particle detectors will also be placed on board each LISA S/C. This work reports on an empirical method that allowed us to disentangle the interplanetary and onboard-generated components of the magnetic field by using the LPF magnetometer measurements. Moreover, we estimate the number and fluence of solar energetic particle events expected to be observed with the ESA Next Generation Radiation Monitor during the mission lifetime. An additional cosmic-ray detector, similar to that designed for LPF, in combination with magnetometers, would permit to observe the evolution of recurrent and non-recurrent galactic cosmic-ray variations and associated increases of the Interplanetary Magnetic Field at the transit of high-speed solar wind streams and interplanetary counterparts of coronal mass ejections. The diagnostics subsystem of LISA makes this mission also a natural multi-point observatory for space weather science investigations

Evidence for local particle acceleration in the first recurrent galactic cosmic ray depression observed by Solar Orbiter The ion event on 19 June 2020

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