The midlatitude thermospheric dynamics from an interhemispheric perspective

Using Fabry-Perot interferometers at five midlatitude stations (Boulder, Palmer, Millstone Hill, Mount John, and Kelan) in both hemispheres, we examine the interhemispheric and seasonal variations of midlatitude thermospheric dynamics. We also use the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) to simulate the seasonal changes of winds and the effects from Sub-Auroral Polarization Streams. The observations and TIEGCM simulations show a clear seasonal variation with more westward and equatorward summer winds. The TIEGCM runs overestimate the westward zonal winds and underestimate the electron densities in the northern summer. We believe that the underestimated TIEGCM electron density leads to a weak ion drag effect in the model, and strong westward zonal winds. TIEGCM overestimates the Sub-Auroral Polarization Stream effects on neutral winds in most cases, probably because the empirical Sub-Auroral Polarization Stream model used by the TIEGCM applies an unrealistic persistent electric field for a long period of time (over 3 hr) due to the low temporal resolution of the Kp index.