During its more than 10 year mission, the CHAMP satellite has revealed exciting new observations of the upper F region ionosphere and the thermosphere. Special benefit has been obtained from simultaneous observations of plasma and neutrals, and the magnetic field, which has led to many new findings and insights into the thermosphere-ionosphere system. This chapter reviews these new findings at low and equatorial latitudes, from the point of view of coupling between the atmosphere and the magnetic field and between different atmospheric regions. Gross features in the electron density and temperature and in the neutral density and wind are tackled, such as the equatorial anomaly, the electron temperature morning overshoot, equatorial plasma irregularities, the zonal wind jet, terminator waves, or findings of the wave-4 structure in plasma and neutrals. For specific examples, it is demonstrated that results of physical models have large impact in understanding the new observations and underlying processes. Examples include the distribution of electron temperature during the morning that is suggested to follow the inclination of the geomagnetic field and the longitudinal wave-4 structures in the plasma and neutrals that are believed to be generated by the same source but through different coupling mechanisms. It is also demonstrated that even the most sophisticated models cannot fully reproduce observations of even large-scale ionospheric and thermospheric features.
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