Magnetotail earthward-propagating fast plasma flows provide important pathways for magnetosphere-ionosphere coupling. This study reexamines a flow-related red-line diffuse-like aurora event previously reported by Liang et al., (2011), utilizing THEMIS and ground-based auroral observations from Poker Flat. We find that time domain structures (TDSs) within the flow bursts efficiently drive electron precipitation below a few keV, aligning with predominantly red-line auroral intensifications in this non-substorm event. The diffuse-like auroras sometimes coexisted with or potentially evolved from discrete forms. We forward model red-line diffuse-like auroras due to TDS-driven precipitation, employing the time-dependent TREx-ATM auroral transport code. The good correlation (0.77) between our modeled and observed red line emissions underscores that TDSs are a primary driver of the red-line diffuse-like auroras, though whistler-mode wave contributions are needed to fully explain the most intense red-line emissions.

The influences of subauroral polarization streams (SAPS) on storm-enhanced density (SED) and tongue of ionization (TOI), an important topic in the field of magnetosphere-ionosphere-thermosphere coupling, however, remain undetermined. The Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) with/without an empirical SAPS model has been used to investigate the impacts of SAPS on SED and TOI. The modeled TEC and ion drift velocities agree reasonably well with the observations of GNSS and DMSP satellites on 17 March 2013. The TIEGCM simulations show that SAPS can significantly affect the electron density of SED and TOI depending on the relative location of SAPS and SED. SAPS reduces the electron density at the eastward edge of SED where they are overlapped, and enhances SED at its westward edge. A term-by-term analysis of the O+ ion continuity equation in the F-region shows that the electron density depletions at the eastward edge of SED are mainly due to increased local plasma loss rates because of SAPS elevated plasma-neutral temperatures and O/N2 reduction because of thermosphere upwelling. The electron density enhancements in the westward edge of SED are mainly due to SAPS-induced westward plasma E×B transports and O/N2 increment because of thermospheric downwelling. Moreover, SAPS-induced electron depletions in the throat region weaken TOI as plasmas undergo anti-sunward convection into the polar cap.

In this letter, we present the results of a conjunction between the SAMPEX satellite and a THEMIS all-sky imager in Gillam, Canada—showing a high correlation between relativistic, >1 MeV, electron microbursts and a type of pulsating aurora called patchy aurora. The correlation was 0.8, and is not serendipitous. While the relationship between pulsating aurora and 10-100s keV microbursts has been previously predicted, here we show a strong association between keV and MeV electron dynamics—possibly spanning two orders of magnitude. Importantly, this result shows that the dynamics of relativistic radiation belt electrons are at times intimately tied to keV electron precipitation, and can not be studied in isolation.

The subauroral ion drift (SAID) denotes a latitudinally narrow channel of fast westward ion drift in the subauroral region, often observed during geomagnetically disturbed intervals. The recently recognized subauroral optical phenomena, the Strong Thermal Emission Velocity Enhancement (STEVE) and the Picket Fence, are both related to intense SAIDs. In this study, we present a 2D time-dependent model simulation of the self-consistent variations of the elec-tron/ion temperature, density, and FAC, under strong SAID, with more focus in the lower ionosphere. Our simulation reproduces many key features of SAID, such as the anomalous electron heating in the E-region, the strong electron temperature enhancement in the upper F-region, the intense ion frictional heating, and the plasma density depletion. Most importantly, the ion Pedersen drifts is found to play a crucial role in the density variations and FAC dynamics in the lower ionosphere. The transport effect of ion Pedersen drifts leads to strong density depletion in the lower ionosphere in a large portion of SAID. The FAC inside SAID is mainly downward with magnitude ï¿¿ ~1 ï¿¿A/m 2. At the poleward edge of SAID, the ion Pedersen drift leads to a pileup of the plasma density and an upward FAC. Our simulation results also corroborate the presence of strong gradients of plasma density, temperature, and flows, at the edge of SAID, which may be conducive to certain plasma instabilities. Our model provides a useful tool for the future exploration of the generation mechanisms of STEVE and Picket Fence.

The sub-auroral ion drift (SAID) denotes a latitudinally narrow channel of fast westward ion drift in the sub-auroral region. The recently recognized sub-auroral optical phenomenon, the Strong Thermal Emission Velocity Enhancement (STEVE), is intrinsically related to intense SAIDs. Recently, we had developed a 2D time-dependent model to study the self-consistent variations of the ionosphere under intense SAID. The present study further advances the model to a current generator scenario of SAID. By assuming magnetospheric field-aligned current (FAC) inputs based on existing knowledge and observations, we model the self-consistent variations of the ionosphere, with focus on the dynamic changes of the plasma density, the Pedersen conductance, and the electric field. We can reproduce the self-consistent evolution of an intense SAID and its associated ionospheric dynamics such as extreme heating and depletion. We illustrate that the ion Pedersen drifts can cause dynamic density variations in the lower ionosphere. Positive feedback is found to exist between the self-consistent variations of the electric field and the conductance: the ion Pedersen transport associated with the electric field leads to density depletion in the lower ionosphere, thus reducing the Pedersen conductance and further enhancing the electric field there. We conclude that such positive feedback is key to the formation of intense SAID’s in the ionosphere.