Nighttime Enhancements in the Midlatitude Ionosphere during Local Winter: Effects of Downward Diffusion and Neutral Wind

Abstract:

Radio occultation (RO) electron density profiles (EDPs) by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) are utilized to investigate nighttime enhancements in the midlatitude ionosphere during local winter. Their dependences on altitude, longitude and geomagnetic latitude are analyzed. Since there are no ionization sources, transport processes caused by downward diffusion and neutral wind should be responsible. Then here comes the question whether and how the two mechanisms work together to induce the enhancements. Therefore we put forward a brief calculation to study the corresponding fluxes and their contributions to nighttime electron density in the midlatitude using COSMIC measurements and several empirical models. By comparing calculation results with observations we quantitatively discuss the effects of these mechanisms on the enhancements.