Comprehensive Pattern of the Ionospheric Troughs Localization in the Winter Southern Hemisphere

Abstract A comprehensive pattern of localization of ionization troughs has been constructed for all local time hours. It includes high‐latitude troughs (HLT), main (or sub‐auroral) troughs (MIT), mid‐latitude ring ionospheric troughs (RIT), low‐latitude troughs (LLT), and quasi‐troughs. The CHAMP satellite data recorded in the southern hemisphere for quiet geomagnetic conditions under high solar activity were used. The separation of HLT and MIT was based on the model of auroral diffuse precipitation (Vorobjev et al., 2013). This model describes zone I of diffuse precipitation at the equatorward edge of the auroral oval and zone II of diffuse precipitation at its poleward edge. To distinguish between MIT and RIT the dynamics of both troughs during geomagnetic disturbances was examined. Because the position of all ionospheric structures, including the auroral oval, depends on longitude, the analysis in each local time sector was conducted within the framework of the longitudinal effect. Each local time sector exhibits specificity. (a) The noon sunlit ionosphere is strongly influenced by the dayside cusp; MIT occurs only at shadow longitudes. (b) In the daytime, strong plasma peaks are observed at latitudes of diffuse precipitation in zone I. (c) In the afternoon/evening sector, the plasma peaks are often observed equatorward of the auroral oval. Both peaks are sometimes accompanied by a quasi‐trough. (d) In the evening, HLT sometimes appears slightly equatorward of auroral oval. (e) In the nighttime, at longitudes of America and the Atlantic, a wide electron density minimum is formed near the Polar circle, which masks the MIT minimum.