Modelling energetic particles in the vicinity of high-speed solar wind streams with PARADISE

Abstract:

Corotating interaction regions (CIRs) are an important source of energetic particles in the heliosphere. These particles are believed to be mainly accelerated in the high amplitude compression waves bounding CIRs. To allow efficient particle acceleration, these waves need to steepen sufficiently which typically only happens at distances past the orbit of Earth. However, the detection of isotropic and low energy particle populations at small radial distances near high-speed streams (HSS) might suggest the presence of local acceleration mechanisms (e.g., Allen et al. 2020).

In this work we use the particle transport model PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration) to study the transport and acceleration of supra-thermal ions in the vicinity of HSSs. PARADISE models the evolution of energetic particle populations propagating in a solar wind generated by the data-driven three-dimensional magnetohydrodynamic model EUHFORIA (EUropean Heliospheric FORecasting Information Asset). The latter model is used to generate solar wind configurations that contain HSSs, in which we subsequently inject supra-thermal ions at a continuous rate. We discuss which properties HSSs need to have in order to produce and sustain energetic particle populations through e.g., diffusive shock or compressional acceleration mechanisms. We investigate how the properties of such energetic particle populations change from large heliocentric radial distances where the CIR shock waves are formed (>1 AU) to the smaller radial distances visited by Parker Solar Probe and Solar Orbiter.