Modeling subauroral polarization streams during the 17 March 2013 storm

Abstract

The subauroral polarization streams (SAPS) are one of the most important features in representing magnetosphere-ionosphere coupling processes. In this study, we use a state-of-the-art modeling framework that couples an inner magnetospheric ring current model RAM-SCB with a global MHD model Block-Adaptive Tree Solar-wind Roe Upwind Scheme (BATS-R-US) and an ionospheric potential solver to study the SAPS that occurred during the 17 March 2013 storm event as well as to assess the modeling capability. Both ionospheric and magnetospheric signatures associated with SAPS are analyzed to understand the spatial and temporal evolution of the electrodynamics in the midlatitude regions. Results show that the model captures the SAPS at subauroral latitudes, where Region 2 field-aligned currents (FACs) flow down to the ionosphere and the conductance is lower than in the higher-latitude auroral zone. Comparisons to observations such as FACs observed by Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), cross-track ion drift from Defense Meteorological Satellite Program (DMSP), and in situ electric field observations from the Van Allen Probes indicate that the model generally reproduces the global dynamics of the Region 2 FACs, the position of SAPS along the DMSP, and the location of the SAPS electric field around L of 3.0 in the inner magnetosphere near the equator. The model also demonstrates double westward flow channels in the dusk sector (the higher-latitude auroral convection and the subauroral SAPS) and captures the mechanism of the SAPS. However, the comparison with ion drifts along DMSP trajectories shows an underestimate of the magnitude of the SAPS and the sensitivity to the specific location and time. The comparison of the SAPS electric field with that measured from the Van Allen Probes shows that the simulated SAPS electric field penetrates deeper than in reality, implying that the shielding from the Region 2 FACs in the model is not well represented. Possible solutions in future studies to improve the modeling capability include implementing a self-consistent ionospheric conductivity module from inner magnetosphere particle precipitation, coupling with the thermosphere-ionosphere chemical processes, and connecting the ionosphere with the inner magnetosphere by the stronger Region 2 FACs calculated in the inner magnetosphere model.

Space Weather Effects Produced by the Ring Current Particles

“…showed that they were directly linked to the partial ring current localized pressure peak, and other observations and numerical modeling has confirmed and further quantified this relationship (e.g. Garner et al 2004;Mishin and Burke 2005;Yu et al 2015;Yuan et al 2016;Califf et al 2016). SAPS are relatively stable during storms, being a persistent feature across the evening sector that can last for many hours (e.g.…”

Large‐Scale Structure of Subauroral Polarization Streams During the Main Phase of a Severe Geomagnetic Storm

“…Through a comparison with the modeling by the Rice Convection Model, Clausen et al () found a good agreement between the longitudinal distribution of the plasma pressure gradients in the RC and the SAPS variation with MLT. Other global simulation work (e.g., Goldstein et al, ; Wang, Lühr, & Ma, ; Yu et al, ; Zheng et al, ) also demonstrated that the subauroral plasma flow was a direct manifestation of the distributions of the RC and ionospheric conductivity, especially during magnetically disturbed periods.…”

SAPS/SAID revisited: A causal relation to the substorm current wedge

“…We next explore the subauroral events detected by the Van Allen Probes during first hours of the St. Patrick's day 2013 and 2015 major storms. On 17 March 2013, the arrival of a solar wind shock initiated a sequence of substorms driven by solar wind pressure pulses and oscillations of the IMF B Z [e.g., Yu et al ., , Figure 2; Foster et al ., ]. The first substorm, with two active phases starting at 06:00 and 06:35 UT, led to AE ≈1100 nT at ≈06:43 UT.…”