Ion Interaction With Rotational Discontinuities: The Role of Polarization Electric Fields in Ion Heating

Ion energization and magnetic field energy dissipation within kinetic‐scale plasma structures is an important problem of space plasma physics. A representative category of such structures consists of magnetic field discontinuities (or thin current sheets), which are widely observed in the solar wind and planetary magnetotails. As these discontinuities move through the ambient plasma, they generate convection electric fields that accelerate ions interacting with them. This acceleration process can be further modified by polarization electric fields that arise due to ion and electron decoupling around strong magnetic field gradients. We investigate ion interactions with moving polarized discontinuities in four distinct space plasma environments: the magnetotails of Earth and Mars, magnetodisk of Jupiter, and the near‐Earth solar wind. Using multi‐mission data sets, we characterize the convection and polarization electric fields by the magnitude of plasma flows along the discontinuity, , and the electron‐to‐ion temperature ratio . Discontinuities in Earth's magnetotail and Jovian magnetodisk are typically slow ( smaller than the ion thermal velocity) and feature hot ions , whereas solar wind discontinuities are fast ( exceeding the ion thermal velocity) and dominated by hot electrons . Martian magnetotail discontinuities can exhibit intermediate properties between these two regimes. We develop a theoretical model describing ion interactions with moving polarized discontinuities and quantify the respective roles of convection and polarization electric fields in ion acceleration. Main model predictions are compared with spacecraft observations and discussed in the context of heavy ion energization across the four examined space plasma systems.