This paper concurrently investigates the midlatitude trough and the plasmapause positions in the ionosphere by colocated measurements of the electron density, electron temperature, and whistler count probed by DEMETER (Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions) satellite in the nighttime at 2230 LT (local time; 1900–0100 MLT, magnetic local time, mainly in the premidnight period) during the 4‐year period of 2006–2009. More than 13,000 Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions orbits of the electron density and the electron temperature are used to search the trough position, while the same amount of the whistler count is employed to determine the plasmapause position at the satellite altitude. The plasmapause is more sensitive to solar activity, which moves equatorward 1.0–1.2° form the low to high solar activity of the study period. On the other hand, the midlatitude trough is more sensitive to seasonal variation, which shifts poleward 1.7–2.5° from the winter to summer month in the study period. The midlatitude trough usually appears in the poleward side of the plasmapause during the study period. Both of the midlatitude trough and the plasmapause move equatorward during the magnetic disturbed condition. For the magnetic disturbed Kp ≥ 6−, the midlatitude trough can appear in the equatorward side of the plasmapause.

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This paper explores multi-instrument space-borne observations in order to validate physical concepts of Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) in relation to major seismic events. In this study we apply already validated observation to identify atmospheric and ionospheric precursors associated with some of recent most destructive earthquakes: M8.6 of March 25, 2005 and M8.5 September 15, 2007 in Sumatra, and M7.9 May 12, 2008 in Wenchuan,\ud China. New investigations are also presented concerning these three earthquakes and for the M7.3 March 2008 in the Xinjiang-Xizang border region, China (the Yutian earthquake). It concerns the ionospheric density, the Global Ionospheric Maps (GIM) of the Total Electron Content (TEC), the Thermal Infra-Red (TIR) anomalies, and the Outgoing Longwave Radiation (OLR) data. It is shown that all these anomalies are identified as short-term precursors, which can be explained by the LAIC concept proposed by Pulinets and Ouzounov (2011)

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<p>This paper investigates the plasmapause positions in the ionosphere by measurement of the whistler count probed by DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite in the daytime at 1030 LT (local time) and the nighttime at 2230 LT during 2005-2010.  The whistler finds the plasmapause position which can be clearly allocated in both daytime and nighttime.  We examine the nighttime/daytime plasmapause in various longitudes, solar activities, seasons, and geomagnetic actives.  Results show that the daytime plasmapause appears in the equatorward side of the nighttime one.  Both the daytime and nighttime plasmapause are sensitive to solar activity, which move equatorward form the low to high solar activity in the study period.  The seasonal variation of the plasmapause are rather random and insignificant.  During magnetic disturbed condition, the plasmapause tend to move equatorward.</p>