Magnetospheric Source and Electric Current System Associated With Intense SAIDs. Issue 22 (18th November 2021) - Wang, Wenrui
Abstract: Subauroral Ion Drifts (SAIDs) are fast azimuthal plasma flows in the ionosphere. In this study, we use the Rice Convection Model to simulate an extremely intense SAID event which may trigger atmospheric emission phenomenon by specifying consecutive low‐entropy bubble injections. The results show strong SAID flow faster than ∼5, 000 m/s that lasts longer than 100 min. Our model indicates that SAIDs map to the sharp inner edge of a strongly enhanced partial ring current, which connects to a Region‐2 downward field‐aligned current (FAC). The simulation predicts that the peak of the SAIDs, the center of the downward FAC, the subauroral boundary, the plasmapause, the inner edge of the proton and electron partial ring current, and the maximum azimuthal drift in the magnetosphere are pressed tightly within 0.5° latitude or 0.2 Re in the equatorial plane. Plain Language Summary: SAIDs (Subauroral Ion Drifts) are very fast westward drift equatorward of the auroral region, and when the velocity reaches up to ∼5, 000 m/s, we call them intense SAIDs. However, how the intense and long‐lasting SAIDs are formed remains unclear. Using the Rice Convection Model, we numerically simulated intense SAIDs which confirms a number of previous observations. The simulation results show a substantially enhanced ring current pressure in the inner magnetosphere as a result of multiple injections, which is identified as the magnetospheric root of intense SAIDs. We also find that several notable structures in the plasma, electric field, and magnetic field distributions are colocated within a very narrow region, which can be tested using conjugate observations in the magnetosphere and in the ionosphere. Key Points: Rice convection model is used to simulate the M‐I coupling of intense and long‐lasting Subauroral Ion Drifts (SAIDs) Consecutive bubble injections lead to a strongly enhanced partial ring current and Region‐2 field‐aligned currents The simulation predicts that the very strong SAID maps to the inner edge of the partial ring current at L ≈ 4 Re