Phase reversal of the diurnal cycle in the midlatitude ionosphere

摘要: [1] The typical diurnal cycle of the midlatitude F region electron density consists a midday maximum and midnight minimum. However, phase reversal this has been found to occur in three distinct regions on globe. They are East Asian (EA) centered around (53°N, 150°E), Northern Atlantic (NA) (45°N, 50°W) South Pacific (SP) (60°S, 110°W). The intensively reported Weddell Sea Anomaly falls inside SP region. occurs during March–August EA NA regions, between August March region, being most prominent local summer. Furthermore, anomaly is more pronounced at solar minimum than maximum, terms larger magnitude months it lasts year. It emphasized that not only nighttime enhancement, but also concurrent noontime depletion. Hence, summer enhancements previous studies just part reversed cycle. cause for involves several interplaying physical processes. Among these, neutral wind combined with geomagnetic field configuration plays pivotal role. generates one-wave longitudinal pattern southern middle latitudes two-wave northern latitudes, whose wave peaks correspond center SP, EA, respectively. seasonal variation winds downward motion ionization induced by thermal contraction ionosphere sunset may largely control occurring time enhancement how long persists different months. as result close ion-neutral coupling. further noted winter NA, very weak or missing.