Austral thermospheric wind circulation and interplanetary magnetic field orientation

Ground‐based high‐resolution spectral measurements of the OI ¹D emission at 15,867 K (630 nm; 1 K = 1 cm−1) from thermospheric altitudes at the geographic south pole are used to determine the relationship between the southern hemisphere high‐latitude thermospheric wind circulation and the interplanetary magnetic field (IMF) during the austral winter of 1989. A clear dependence is shown between the thermospheric wind direction and magnitude and the IMF. In the midnight sector, the zonal wind magnitude is dependent on By, and the meridional component on Bz. The magnetic local times of the largest polar cap electric fields are also inferred for either sign of By. In addition, it is shown that the field angle Φ of the IMF in the Y–Z plane is also useful for ordering the neutral wind data. These ground‐based wind measurements also reflect the polarity and magnitude of the IMF, at least near the observing station's magnetic midnight.