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Abstract: This paper presents the results of modeling the ionospheric effect of the seismogenic electrostatic field (SEF) seen at the earth’s surface as a perturbation of the vertical atmospheric electrostatic field in the earthquake preparation zone. The SEF distribution at ionospheric altitudes is obtained as an analytical solution of the continuity equation for the electric current density. It is shown that at night, the horizontally large scale SEF can efficiently penetrate into the ionosphere and produce noticeable changes in the horizontal distribution of the F region electron density. The results suggest that the seismogenic electrostatic field could be a possible source for the ionospheric variations observed over Taiwan before the strong Chi Chi earthquake of September 21, 1999. [Copyright &y& Elsevier]

Abstract: The equatorial electric field plays an important role in low-latitude ionospheric plasma drift and its distribution at both quiet and disturbed periods, which should be involved in low-latitude ionospheric correction and prediction models. In this paper, an empirical model is established and utilized in real-time ionospheric correction, which contains the affiliation between the ionospheric disturbances and their electric field origins. This model is built using the nonlinear relations between ionospheric foF2 data from two low-latitude ionosondes and equatorial disturbance field data from an empirical model during fifty storms. The performance of the model during twelve intense storms is evaluated and compared with another empirical correction model, STORM. The latter relies on that long-lived negative storm effects are induced by neutral composition changes. The results of our model show that some sharp increase of foF2 could be captured, whereas STORM only gives the probable estimations. The averaged correction error is reduced by 17%, comparing with STORM. This indicates that the disturbance of the electric fields are also important in low-latitude storm-time ionospheric corrections. [Copyright &y& Elsevier]

Abstract: In this paper, we use the modified GSM TIP model to explore how the thermosphere–ionosphere system in the American longitudinal sector responded to the series of geomagnetic storms on September 9–14, 2005. Comparison of modeling results with experimental data at Millstone Hill, USA (42.6°N, 71.5°W), Ramey, Puerto Rico (18.3°N, 66.8°W) and Jicamarca, Peru (11.9°S, 76.9°W) has shown a good agreement of ionospheric disturbances in the F-region maximum height. We examine in detail the formation mechanisms of these disturbances at different latitudes and describe some of the important physical processes affecting the behavior of the F-region. In addition, we consider the propagation of thermospheric wind surge and the formation of additional layers in the low-latitude ionosphere during geomagnetic storms. [Copyright &y& Elsevier]

Abstract: This paper presents a mathematical model to simulate ionospheric plasma drifts at equatorial low latitude regions by coupling of E- and F-regions. The governing non-linear differential equations (of elliptic and parabolic nature) are solved numerically through finite-difference schemes and obtained neutral winds and electric fields. The temperature and electron density profiles are generated utilizing MSIS-86 atmospheric model. The continuity equation is employed to obtain night-time E-region density profile using measured ionograms at Trivandrum (India). The computed vertical and zonal plasma drifts are comparable with measured Jacamarca plasma drifts with little variations during noon and evening times. The plasma drifts at Trivandrum (8.5° N, 76.5° E, dip 0.5° N) are compared with those of Jicamarca (12° S, 76.9° W, dip 2° N). Neutral wind simulations of present model agree well with those of horizontal wind model (HWM-93). The post-sunset enhancement and its reversal are also discussed. [ABSTRACT FROM AUTHOR]