Energetic Protons at Solar Orbiter Shocks: Efficiency, Variability, and Energetic Particle Pressure-Dominated Events

Interplanetary (IP) shocks are driven by solar activity and provide a unique in situ laboratory for studying particle acceleration. With its high-resolution measurements in the suprathermal range (above ~10 keV), Solar Orbiter opens a new window on how particles are energized out of the thermal population.We focus on energetic proton production at IP shocks observed by Solar Orbiter, presenting results from a systematic calculation of proton acceleration efficiency and discussing its variability across 150 events observed since launch. We then highlight a subset of particularly strong shocks where the energetic particle pressure exceeds the combined magnetic and thermal pressure, a regime with direct relevance to cosmic-ray shocks in astrophysical environments. For these shocks, we examine the details of the local plasma and magnetic field conditions, with focus on upstream fluctuations and their role in particle acceleration. Together, these results provide new insight into how shocks accelerate particles across both heliospheric and broader astrophysical environments.