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We investigate the sources of the variation of the high-latitude thermospheric neutral mass density depending on the\udinterplanetary magnetic field (IMF) conditions. For this purpose, we have carried out the National Center for Atmospheric\udResearch Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM) simulations\udfor various IMF conditions under summer condition in the southern hemisphere. The NCAR-TIEGCM is combined with\uda new empirical model that provides a forcing to the thermosphere in high latitudes. The difference of the high-latitude\udthermospheric neutral mass density (subtraction of the values for zero IMF condition from the values for non-zero IMF\udconditions) shows a dependence on the IMF condition: For negative By condition, there are significantly enhanced difference\uddensities in the dusk sector and around midnight. Under the positive-By condition, there is a decrease in the\udearly morning hours including the dawn side poleward of -70°. For negative Bz, the difference of the thermospheric\uddensities shows a strong enhancement in the cusp region and around midnight, but decreases in the dawn sector. In\udthe dusk sector, those values are relatively larger than those in the dawn sector. The density difference under positive-Bz\udcondition shows decreases generally. The density difference is more significant under negative-Bz condition than under\udpositive-Bz condition. The dependence of the density difference on the IMF conditions in high latitudes, especially, in\udthe dawn and dusk sectors can be explained by the effect of thermospheric winds that are associated with the ionospheric\udconvection and vary following the direction of the IMF. In auroral and cusp regions, heating of thermosphere\udby ionospheric currents and/or auroral particle precipitation can be also the source of the dependence of the density\uddifference on the IMF conditions

Sources of the High-Latitude Thermospheric Neutral Mass Density Variations