Grand Challenge Research on Subauroral Polarization Streams

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Monday, June 5, 2017

A team from the NCAR High Altitude Observatory, Johns Hopkins University, and Rice University, led by HAO scientist Wenbin Wang, was awarded a prestigious NASA Heliophysics Grand Challenge Research Grant to study the magnetosphere-ionosphere interaction known as subauroral polarization streams.

Joule heating of the ionosphere simulated by the NCAR TIE-GCM image
Joule heating of the ionosphere simulated by the NCAR TIE-GCM, with a sub-auroral polarization stream imposed. The two arcs near the pole are caused by auroral heating during a geomagnetic disturbance, and the arc to the far left in the evening sector, around 18 local time, is caused by the polarization stream.

Subauroral polarization streams are narrow bands of high-speed plasma drifts located in a region that is just outside of the auroral oval of electron precipitation, where downward currents from the inner magnetosphere flow through a region of low conductivity. A full description of the fundamental physical processes that govern the occurrence, characteristics, variations and effects of these streams is still elusive and challenging, because it will require a systematic approach involving high-resolution, first principles simulations and comprehensive observations. The project will explore these physical processes, their changes with solar wind and geophysical conditions, and their effects on the coupled magnetosphere-ionosphere system, through numerical simulations and model-data comparisons.

A high-resolution version of the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) model will be employed in the studies. This model combines the Lyon-Fedder-Mobarry global magnetosphere code, the inner magnetosphere Rice Convection Model, and the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). Magnetosphere data from the Van Allen Probes, thermosphere composition and auroral data from the TIMED mission, and auroral data from the NSF AMPERE and SuperDARN projects will be used in the studies. Data-model comparisons will enable the team to investigate the causes of the subauroral polarization streams and their dynamic impacts on the ionosphere-thermosphere system.