Modeling Study of the Geospace System Response to the Solar Wind Dynamic Pressure Enhancement on 17 March 2015

Abstract

The global magnetosphere‐ionosphere‐thermosphere system is intrinsically coupled and susceptible to external drivers such as solar wind dynamic pressure enhancements. In order to understand the large‐scale dynamic processes in the magnetosphere‐ionosphere‐thermosphere system due to the compression from the solar wind, the 17 March 2015 sudden commencement was studied in detail using global numerical models. This storm was one of the most geoeffective events of the solar cycle 24 with a minimum Dst of −222 nT. The Wind spacecraft recorded a 10‐nPa increment in the solar wind dynamic pressure, while the interplanetary magnetic field BZ became further northward. The University of Michigan Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme global magnetohydrodynamic code was utilized to study the generation and propagation of perturbations associated with the compression of the magnetosphere system. In addition, the high‐resolution electric potential and auroral power output from the magnetohydrodynamic model was used to drive the global ionosphere‐thermosphere model to investigate the ionosphere‐thermosphere system response to pressure enhancement. During the compression, the electric potentials and convection patterns in the polar ionosphere were significantly altered when the preliminary impulse and main impulse field‐aligned currents moved from dayside to nightside. As a result of enhanced frictional heating, plasma and neutral temperatures increased at the locations where the flow speeds were enhanced, whereas the electron density dropped at these locations. In particular, the region between the preliminary impulse and main impulse field‐aligned currents experienced the most significant heating with 1000‐K ion temperature increase and 20‐K neutral temperature increase within 2 min. Comparison of the simulation results with the Poker Flat Incoherent Scatter Radar observations showed reasonable agreements despite underestimated magnitudes.Plain Language SummaryDuring 17 March 2015, near‐Earth environment was significantly perturbed due to an interplanetary shock. Using numerical models, we studied the effect of this shock on the geospace system. We have found that the compression due to the shock can affect the Earth’s upper atmosphere immediately. The shock created various perturbations including but not limited to temperature and density variations, at low‐Earth orbit altitudes, which are very important for spacecraft operations. Ground‐based measurements supported our findings and revealed that the perturbations occurring were even more drastic than we modeled.Key PointsShock‐induced compression significantly alters the high‐latitude convection patternsLarge convection speed between PI and MI FACs caused significant frictional heating and subsequent heat transfer between ions and neutralsThe simulation results in general reproduce observations despite lower magnitudes