| Summary: | The ratio value – known as plasma parameter “beta” (β) - of the interplanetary-plasma pressure (thermal pressure) to themagnetic field’s (magnetic pressure) or of their energy densities, is critical for the space plasmas and has important consequencesto their properties. Although in the scientific literature the contribution of the supra-thermal particles to the plasmapressure is generally assumed negligible, we deduced, by analyzing energetic particles and magnetic field measurementsrecorded by the Ulysses spacecraft, that in a series of events, the energy density contained in the supra-thermal tail of theparticle distribution is comparable to or even higher than the energy density of the magnetic field, creating conditions ofhigh-beta plasma. In particular, in this paper we analyze Ulysses measurements of the energy density ratio (parameter βep) ofthe supra-thermal (20 keV to ~5 MeV) ions’ (by the HI-SCALE instrument) to the magnetic field’s (by the VHM/FGM instrument)in order to find occurrences of high-beta (βep >1) supra-thermal plasma conditions in the vicinity of interplanetaryshock-waves. These high-beta ion events are associated with energetic particle intensity enhancements which have beenproduced by reacceleration at the shock fronts.
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