Proton energy spectra of energetic storm particle events and magnetic field turbulent fluctuations nearby the associated interplanetary shocks

Interplanetary shocks are efficient sources of accelerated particles and are often associated with high-energy proton/ion flux enhancements known as energetic storm particle (ESP) events. In situ spacecraft observations of particle fluxes near the shocks can be used to obtain energy spectra, providing very useful information for the investigation of the acceleration mechanisms. In this work we analysed the kinetic energy spectra of proton flux enhancements associated with ESP events observed by various spacecraft. ESP events associated with diverse shock conditions and geometries (e.g. quasi-perpendicular and quasi-parallel) were investigated. In addition, some of the events occurred during intervals in which Solar Energetic Particle (SEP) events were also ongoing, providing a background of pre-accelerated particles. The analysis of the shape of the observed spectra was used to identify which are the most plausible acceleration mechanisms at work. The turbulent magnetic field fluctuations upstream and downstream of the shocks were also studied to the aim of obtaining information about their possible role in particle acceleration.

This research has been carried out in the framework of the CAESAR (Comprehensive spAce wEather Studies for the ASPIS prototype Realization) project, supported by the Italian Space Agency and the National Institute of Astrophysics through the ASI-INAF n. 2020-35-HH.0 agreement for the development of the ASPIS (ASI Space weather InfraStructure) prototype of scientific data centre for Space Weather.