The Coupled Ionosphere and Thermosphere at Mid-Latitudes in the Asian Sector and Its Comparison with Other Locations

Abstract

The present paper reviews dynamical features of the mid-latitude ionosphere and thermosphere in the Asian sector as quantified by the MU radar at Shigaraki, Japan (35°N, 136°E) and compares these with dynamics reported for other locations. The thermospheric wind and temperature in the Asian sector differ from the wind and temperature measured at other mid-latitude locations. Furthermore, the perpendicular plasma drifts have strong resemblances to those predicted by current models, but their seasonal trends suggest a strong conjugate effect that has not been fully incorporated into our expectations of local behavior. These results provide additional evidence that global features cannot be described by a simple zonal mean. Finally, two features related to gravity waves are discussed. Gravity waves seem to be ubiquitous in the thermosphere and play an important role in creating a variety of electron density fluctuations and irregularities in the mid-latitude ionosphere. Tracking the progression of ionospheric gravity-wave effects between MU radar beams has allowed gravity wave packets to be identified and their dispersion relation to be determined. The character of ionospheric irregularities observed are consistent with their seeding by the Perkins mechanism.