The Effect of Field‐Aligned Potential Drop on Electron Precipitation and Ionospheric Conductivity

Abstract Field‐aligned potential drop is an important phenomenon in the magnetosphere‐ionosphere coupling system. Using the kinetic Storm‐Time Ring Current Model (STRIM), which has fulfilled a self‐consistent electric field calculation, we investigate the role of field‐aligned potential drop in regulating the magnetosphere‐ionosphere coupling by incorporating field‐aligned potential drop into the model. It was found that field‐aligned potential drop significantly reduces particles' pitch angle and increases their energies, equivalently broadening their bounce loss cone and enhancing magnetospheric particle precipitation. In regions where the potential drop reaches several kilovolts, the discrete precipitating electron flux driven directly by the potential drop becomes dominant over the diffuse precipitation, contributing over 90% to the total precipitation. The associated average energy is also enhanced by up to ∼60%, compared to cases without a strong field‐aligned potential drop. The ionospheric conductivity of the regions with discrete electron precipitation was further evaluated by the GLOW model. It is found that Pedersen and Hall conductance in the E region (∼150 km in height) are almost entirely controlled by discrete precipitation if the field‐aligned potential drop is over 10 kilovolts. These results provide quantitative evidence that field‐aligned potential drop strongly modulates the intensity and energy spectrum of precipitating particles and substantially influences the ionospheric electrodynamics.