SAPS in the 17 March 2013 Storm Event: Initial Results From the Coupled Magnetosphere‐Ionosphere‐Thermosphere Model

Abstract

Subauroral polarization stream (SAPS) is latitudinally narrow flow channels of large westward plasma drifts in the subauroral ionosphere. In this study, the global structure and dynamic evolution of SAPS are investigated by using the Coupled Magnetosphere‐Ionosphere‐Thermosphere model with ring current extension, namely, the Lyon‐Fedder‐Mobarry‐Thermosphere Ionosphere Electrodynamics General Circulation Model‐Rice Convection Model, to simulate the 2013 St. Patrick's Day storm event. This is the first time that the global distribution and temporal evolution of SAPS are investigated using first‐principle models. The model shows a strong westward ion drift channel formed equatorward of the auroral electron precipitation boundary on the duskside, which is identified as the SAPS structure. The simulated ion drift velocity and auroral electron precipitation sampled along the trajectory of the Defense Meteorological Satellite Program F18 satellite are in good agreement with the satellite measurements. SAPS initiate in the predusk sector when the interplanetary magnetic field turns southward. SAPS latitude generally decreases with magnetic local time from dusk to midnight. The SAPS channel shows wedge, inverse wedge, and crescent morphologies during the storm and becomes discontinuous when the interplanetary magnetic field is weakly southward. The SAPS mean latitude has a correlation coefficient of 0.77 with the Dst index. The mean latitude moves equatorward, and the flow channel broadens in the storm main phase. The simulation results illustrate both the global distribution and highly dynamic behavior of SAPS that are not readily apparent from the observation data.

A Statistical Study of the Subauroral Polarization Stream Over North American Sector Using the Millstone Hill Incoherent Scatter Radar 1979–2019 Measurements

“…It can be seen that both SAPS flow and ion vertical flow are much stronger when the IMF clock angle is between −180° and −90° (i.e., negative By and negative Bz ). For IMF Bz dependence, other studies indicate that SAPS will move equatorward with a larger magnitude when IMF Bz becomes stronger southward, a condition often associated with enhanced geomagnetic activity and extended convection pattern (Horvath & Lovell, 2016; Lin et al, 2019). For IMF By dependence, it is known that the main effect of By is to change the shape and orientation of the two‐cell convection pattern, in particular when Bz is negative (Heelis, 1984; Heppner & Maynard, 1987; Weimer, 1995).…”

Large‐Scale Ionospheric Disturbances During the 17 March 2015 Storm: A Model‐Data Comparative Study

“…However, their study employed an empirical neutral wind model and therefore did not include the feedback effect between neutrals and ions. Other recent progresses in the area of SAPS research involve fully coupled magnetosphere‐ionosphere‐thermosphere models, with a primary focus on the magnetosphere‐ionosphere coupling processes that produce the SAPS structures during the March 2013 storm (e.g., Lin et al, ; Raeder et al, ). These efforts represent an important advance in understanding the formation of SAPS and its impact on the magnetosphere‐ionosphere‐thermosphere system.…”

A Simulation of the Field‐Aligned Plasma Transport in the Plasmaspheric Plume During the 2015 St. Patrick's Day Storm

“…As we mentioned above, we only focused on the influences of SAPS electric field on the E × B drift of the flux tube and on the field‐aligned cold plasma transport from SED region to the plasmaspheric plume. However, SAPS have been considered to have much more profound effects on magnetosphere‐ionosphere‐thermosphere coupling process (e.g., Lin et al, ; Wang et al, ; Yuan et al, ; Zou et al, ). Moreover, many studies have been conducted on ion flows and transport at high latitudes, which showed that multiple processes are involved (Tu et al, ; Wang et al, ; Yuan et al, ; Zeng & Horwitz, ).…”