Omega bands are mesoscale auroral structures emerging as eastward moving quasi-periodic poleward protrusions well within the closed field line region of the auroral oval. Neither specific conditions of their appearance nor their causes are well understood. We perform a superposed epoch analysis of OMNI and SuperMAG measurements taken during 28 omega band events recorded by auroral all-sky imager (ASI) observations from 2006-2013 to identify their solar wind drivers. We find local enhancements in the solar wind flow speed, magnetic field, pressure, and proton density at the time of the omega band observation. In the magnetosphere-ionosphere, we see enhancements in the ring current, partial ring current, and auroral electrojets. These features are consistent with geomagnetic activity caused by stream interaction regions (SIRs). 19 of our events overlap with SIRs from published event catalogs. Our findings suggest that omega bands are driven by compression regions commonly associated with SIR events.

In this letter, we present the results of a conjunction between the SAMPEX satellite and a THEMIS all-sky imager in Gillam, Canada—showing an unexpected correlation between relativistic, > 1 MeV, electron microbursts and patchy pulsating 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—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.

A new technique for estimating the global-scale pattern of magnetospheric convection in the ionosphere is presented. The technique uses the SuperDARN line-of-sight velocity observations combined with an empirical convection model and the assumption that the resulting velocity field is divergence free. In contrast to other techniques for convection estimation, it does not express the velocity field in terms of known basis vectors and it does not assume that the velocity can be determined from a static potential. The velocity is estimated by applying Bayesian inverse theory to the input data, model, and constraints. Linear equations for the plasma velocity at every point in the domain are solved simultaneously in a least-squares sense. Application of the technique results in convection patterns with spatial resolution equal to the calculation grid. The resulting patterns conform with expectations based on the observed IMF conditions and display features that show close correspondence to simultaneously observed features in the auroral luminosity.

\justify The location of the polar cap boundary is typically determined using low-orbit satellite measurements in which the boundary is identified by its unique signature of a sharp decrease in energy and particle flux poleward of the auroral oval. In principle, this decrease in precipitating particles should appear as a concomitant sharp change in auroral luminosity. Based on a few events, \cite{Blanchard_1995} suggested that a dramatic gradient in redline aurora may also be an indicator of the polar cap boundary. In recent years, advances in capabilities and the deployment of ground-based all-sky imagers have ushered in a new era of auroral measurements. Auroral imaging has moved well beyond the capabilities of the instrumentation in the previous study in terms of both spatial and temporal resolution. We now have access to decades of optical data from arrays spanning a huge spatial range, enabling a fresh examination of the relationship between redline aurora, particle precipitation, and the polar cap open closed boundary. In this study, we use data from the DMSP satellites in conjunction with the University of Calgary’s REGO (630.0nm) data to assess the viability of automated detection of the 2-dimensional polar cap boundary. Our results exhibit good agreement between the optical and particle polar cap boundary and suggest that a luminosity in redline emission could serve as a reasonable proxy for the location of the the electron poleward boundary during, while providing both high temporal and spatial resolution maps of the open-closed boundary.