Nighttime cooling of the protonosphere

This work is a theoretical study of the time-dependent nighttime behavior of the protonosphere. The coupled continuity momentum and heat equations have been solved to obtain the time-dependent temperature and density profiles along two midlatitude geomagnetic field lines from an altitude of 1000 km in one hemisphere to the same altitude in the conjugate hemisphere. Energy and particle fluxes are also deduced from the numerical solution. The total energy conducted down from the protonosphere is sufficient to maintain the electron temperatures above that of the neutrals in the upper F region. The 40° geomagnetic latitude field line is characterized by an initial downward flux of ionization followed by an upward flux during the latter part of the night. The flux along the 50° field line is downward during the entire night with the magnitude of the flux slowly decreasing to zero. The calculated results are also compared with the few experimental data that are available.