The Effect of Subauroral Polarization Streams on Ionosphere and Thermosphere During the 2015 St. Patrick's Day Storm: Global Ionosphere‐Thermosphere Model Simulations

Abstract

AbstractUsing the Millstone Hill incoherent scatter radar observations during 2015 St. Patrick's Day storm, subauroral polarization streams (SAPSs) have been specified in the nonhydrostatic Global Ionosphere‐Thermosphere Model simulations. The results reveal that the effect of SAPS on the coupled thermosphere‐ionosphere system includes the following: (1) Sudden frictional heating of SAPS results in acoustic‐gravity waves in the thermosphere. The vertical oscillation is localized, while the meridional disturbance propagates poleward and equatorward. (2) The SAPS‐associated horizontal wind field includes an enhanced westward wind within SAPS channel and a twin of vortex‐like winds north (clockwise) and south (anticlockwise) of subauroral latitudes. (3) Due to the neutral‐ion drag, ions in the vicinity of SAPS channel oscillate vertically with neutrals, resulting in a perturbation of ~0.3 TECu in ionospheric total electron content. The SAPS‐induced traveling atmospheric disturbances can elevate the plasma and increase the total electron content in midlatitude ionosphere. (4) It is confirmed that the Coriolis force can contribute to the poleward turning of the neutral wind during the post‐SAPS interval. In addition, the traveling atmospheric disturbance induced by the variation of auroral input and high‐latitude convection is possibly the primary cause of the poleward neutral wind surge during the magnetic storm on 17–18 March 2015. The combination of the two factors can make the northward meridional wind surge reach a magnitude of 100 m/s. This study improves our understanding of the SAPS's effect on neutral dynamics and ion‐neutral coupling processes during geomagnetically disturbed intervals.