In this work, we investigate the longitudinal patterns of thermospheric zonal winds (~400 km) and their seasonal and solar activity dependence using CHAllenging Minisatellite Payload cross-track wind data and Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations. CHAllenging Minisatellite Payload data show that there are large longitudinal variations in thermospheric zonal winds. These longitudinal variations do not have significant solar activity dependence. In the northern hemisphere at low and middle latitudes, the daytime zonal winds are more westward between À90°a nd 90°longitudes and more eastward at other longitudes. The nighttime zonal wind direction with pattern is opposite to that in the daytime. In the southern hemisphere at low and middle latitudes, the local time variation of the longitudinal wind structure, including positive and negative peak locations, is almost the reverse of that in the northern hemisphere. Thus, the zonal wind patterns also show great hemispheric asymmetry. In addition, the longitudinal patterns of zonal winds in both hemispheres show seasonal variations. The longitudinal patterns during the June solstice are significantly different from those in other seasons. These observational results are well reproduced in TIEGCM simulations. To elucidate the physical processes responsible for the observed and simulated longitudinal patterns of the zonal winds, the TIEGCM is also run for different geomagnetic field configurations. A comparison between the TIEGCM results shows that geomagnetic field structure is the main cause of the large longitudinal variations of thermospheric zonal winds and their local time, hemispheric asymmetry, and seasonal changes at low and middle latitudes.

By using 10 years of Challenging Minisatellite Payload satellite observations, we investigate the average conditions of the interplanetary magnetic field (IMF) prevailing during the westward counter equatorial electrojet (CEJ). Equally, we compared the average IMF conditions accompanying high-latitude field-aligned currents of the Region 1 (R1) and Region 2 (R2). It shows that both CEJ and high-latitude field-aligned currents events when R2 is greater than R1 tend to happen preferably during the northward turning of the IMF Bz and the substorm recovery phase. Sunlight has an important influence on the longitudinal distribution of the equatorial electrojet (EEJ), and the effect is opposite to the tidal electric field at E region. The anticorrelation between cos 0.5 (SZA) (solar zenith angle effect) average values during CEJ events and EEJ intensity is most prominent around June solstice. By using combined measurements from Challenging Minisatellite Payload and DMSP satellites, it is found that before the occurrence and in the initial phase of a subauroral polarization stream the EEJ gets enhanced, and after about 30 min it reduces in intensity. The CEJ occurrence rate more than doubles during subauroral polarization stream periods compared to normal conditions.

Previous studies mostly focused on ionosphere and thermosphere responses to strong southward interplanetary magnetic field (IMF) Bz conditions. However, it is not clear how the ionosphere and thermosphere (IT) system responds to Alfvénic quasi‐periodic oscillating IMF Bz conditions. In this article, simulations by the Coupled Magnetosphere Ionosphere Thermosphere model have been used to investigate the effects of IMF Bz temporal variations with 10‐, 30‐, and 60‐min oscillation periods on the coupled IT system. The simulation results show that the cross polar cap potential and auroral peak electron energy flux are stronger when the IMF Bz oscillation frequency is lower. The relatively small periodic wind responses in the 10‐min IMF oscillation case indicates a low‐pass filter nature of the magnetosphere‐ionosphere‐thermosphere system. Two different thermospheric wind (Vn) responses are revealed. One is the almost simultaneous responses at all latitudes, and the other shows a typical traveling atmospheric disturbances signature with a time delay with respect to the latitude for all UTs. The simultaneous Vn responses at all latitudes appear in the daytime Northern Hemisphere, which are mainly caused by the ion drag force in association with penetration electric fields induced plasma density and ion drifts changes. The short‐period traveling atmospheric disturbances occurring in the nighttime of both hemispheres and the daytime of the Southern Hemisphere propagate from high to low latitudes showing latitudinal dependence. Both responses oscillate with the same frequencies as those of IMF Bz oscillations.