Results from the meridional ionosonde network located in Southeast Asia (SEALION) demonstrate the interesting nature of the F3 layer, showing its generation mechanism. Ionograms obtained on 16 November 2004 and 31 March 2005 at Chiang Mai (CMU; geographic latitude 18.8°N, geographic longitude 98.9°E, and magnetic latitude 13.2°N), Chumphon (CPN; 10.7°N, 99.4°E, and 3.2°N) and Kototabang (KTB; 0.2°S, 100.3°E, and 10.1°S) showed significant differences between CPN near the magnetic equator, and CMU and KTB in the magnetic low-latitude region. The simultaneous magnetic conjugate observations of the F3 layer achieved using the SEALION ionosonde network data showed clear dependences of the F3 layer on the magnetic latitude. It is suggested that these magnetic latitude dependences of the F3 layer can be explained by considering the plasma diffusion effects along the magnetic field lines in the magnetic low-latitude region.
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