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Abstract The inductive component of the magnetospheric electric field, which is associated with the temporal change of magnetic field, provides an additional means of local plasma energization and transport in addition to the electrostatic counterpart. This study examines the detailed response of the inner magnetosphere to inductive electric fields and the associated electric‐driven convection corresponding to different solar wind conditions. A novel modeling capability is employed to self‐consistently simulate the electromagnetic and plasma environment of the entire magnetospheric cavity. The explicit separation of the electric field by source (inductive vs. electrostatic) and subsequent implementation of inductive effects in the ring current model allow us to investigate, for the first time, the effect of the inductive electric field on the kinetics and evolution of the ring current system. The simulation results presented in this study demonstrate that the inductive component of the electric field is capable of providing an additional source for long‐lasting plasma drifts, which in turn significantly alter the trajectories of both thermal and energetic particles. Such changes in the plasma drift, which arise due to the inductive electric fields, further reshape the storm‐time ring current morphology and alter the degree of the ring current asymmetry, as well as the timing and the peak of the ion pressure. The total ion energy is increasing at a faster rate than the supply of energetic ions to the ring current, suggesting that the inductive electric field provides effective and accumulative local energization for the trapped ring current population without confining additional particles. 

Abstract Cold H⁺produced via charge exchange reactions between ring current ions and exospheric neutral hydrogen constitutes an additional source of cold plasma that further contributes to the plasmasphere and affects the plasma dynamics in the Earth's magnetosphere system; however, its production and associated effects on the plasmasphere dynamics have not been fully assessed and quantified. In this study, we perform numerical simulations mimicking an idealized three‐phase geomagnetic storm to investigate the role of heavy ion composition in the ring current (O⁺vs. N⁺) and exospheric neutral hydrogen density in the production of cold H⁺via charge exchange reactions. It is found that ring current heavy ions produce more than 50% of the total cold H⁺via charge exchange reactions, and energetic N⁺is more efficient in producing cold H⁺via charge exchange reactions than O⁺. Furthermore, the density structure of the cold H⁺is highly dependent on the mass of the parent ion; that is, cold H⁺deriving from charge exchange reactions involving energetic O⁺with neutral hydrogen, populates the lower L‐shells, while cold H⁺deriving from charge exchange reactions involving energetic N⁺with neutral hydrogen populates the higher L‐shells. In addition, the density of cold H⁺produced via charge exchange reactions involving N⁺can be peak at values up to one order of magnitude larger than the local plasmaspheric density, suggesting that solely considering the supply of cold plasma from the ionosphere to the plasmasphere can lead to a significant underestimation of plasmasphere density. 

Abstract Charged particles are observed to be injected into the inner magnetosphere from the plasma sheet and energized up to high energies over short distance and time, during both geomagnetic storms and substorms. Numerous studies suggest that it is the short‐duration and high‐speed plasma flows, which are closely associated with the global effects of magnetic reconnection and inductive effects, rather than the slow and steady convection that control the earthward transport of plasma and magnetic flux from the magnetotail, especially during geomagnetic activities. In order to include the effect of the inductive electric field produced by the temporal change of magnetic field on the dynamics of ring current, we implemented both theoretical and numerical modifications to an inner magnetosphere kinetic model—Hot Electron‐Ion Drift Integrator. New drift terms associated with the inductive electric field are incorporated into the calculation of bounce‐averaged coefficients for the distribution function, and their numerical implementations and the associated effects on total drift and energization rate are discussed. Numerical simulations show that the local particle drifts are significantly altered by the presence of inductive electric fields, in addition to the changing magnetic gradient‐curvature drift due to the distortion of magnetic field, and at certain locations, the inductive drift dominates both the potential and the magnetic gradient‐curvature drift. The presence of a self‐consistent inductive electric field alters the overall particle trajectories, energization, and pitch angle, resulting in significant changes in the topology and the strength of the ring current. 

This paper reviews a few important concepts and findings pertaining to the ring current research. Also briefly overviewed are the sources and losses of ring current ions. Recent challenges in modeling and observations of the ring current are presented, as is a brief discussion on open questions.