The low latitude ionospheric effects of the April 2000 magnetic storm near the longitude 120°E

In this paper, we report the responses of the low latitude ionosphere near the longitude 120°E to the April 2000 geomagnetic storm using Digisonde data measured at Chungli (25.0°N, 121.2°E, Mag. 13.8°N), Wuhan (30.6°N, 114.4°E, Mag. 19.3°N), and Kokubunji (35.7°N, 139.5°E, Mag. 25.7°N). At these three stations, the significant ionospheric responses are near-simultaneous height disturbances after the sudden storm commencement (SSC) on April 6, 2000 and wave-like disturbances in the daytime on April 7. The ionospheric height disturbances in the nighttime after the SSC at these stations are suggested to be caused by the storm related perturbed electric fields, and the followed wave-like disturbances may be caused by storm induced atmospheric gravity waves. The vertical effective winds derived from Digisonde measurements imply the existence of significantly large vertical drifts during this storm, which are in agreement with the perturbed zonal electric fields predicted by the model of Fejer and Scherliess (1997) and Scherliess and Fejer (1997). Finally, the storm time derivations of foF2 from its monthly median level at these stations are used to validate the predication ability of the empirical model of Araujo-Pradere et al. (2002), which has included in the International Reference Ionosphere model IRI2000.