Effects of Magnetospheric Lobe Cell Convection on Dayside Upper Thermospheric Winds at High Latitudes

Tuesday, October 4, 2016

This paper investigates a possible physical mechanism of the observed dayside high-latitude upper thermospheric wind using numerical simulations from the coupled magnetosphere-ionosphere-thermosphere (CMIT) model. Results show that the CMIT model is capable of reproducing the unexpected afternoon equatorward winds in the upper thermosphere observed by the High altitude Interferometer WIND observation (HIWIND) balloon.

Average ionospheric potential and DMSP F-16 ion drift observations image
(a) The average ionospheric potential (blue-red contours), field-aligned current (blue-red color) and open-closed boundary (green contour) in the Northern Hemisphere derived from the CMIT simulation between 11:55 and 17:23 UT. The minimum/maximum potential values are indicated in the left bottom corner. (b) The summary of DMSP F-16 ion drift observations between 11:55 and 17:23 UT, together with the simulated average ionospheric potential from CMIT.

Models that lack adequate coupling produce poleward winds. The modeling study suggests that ion drag driven by magnetospheric lobe cell convection is another possible mechanism for turning the climatologically expected dayside poleward winds to the observed equatorward direction. The simulation results are validated by HIWIND, European Incoherent Scatter, and Defense Meteorological Satellite Program. The results suggest a strong momentum coupling between high-latitude ionospheric plasma circulation and thermospheric neutral winds in the summer hemisphere during positive IMF Bz periods, through the formation of magnetospheric lobe cell convection driven by persistent positive IMF By. The CMIT simulation adds important insight into the role of dayside coupling during intervals of otherwise quiet geomagnetic activity.

Submitted to the Geophysical Research Letters, September 2016.