Space based GPS measurements onboard Low Earth Orbiting (LEO) satellites provide a uniquepossibility for exploring the ionosphere on a global scale. Both the radio occultation measurements in thelimb sounding mode and the navigation measurements using a zenith viewing GPS antenna provide theTotal Electron Content (TEC) along numerous ray paths. TEC may effectively be used for re...

The signals from VLF/LF transmitters are known to propagate in the Earth-ionosphere waveguide, so that the subionospheric propagation characteristics are very sensitive to the condition of the lower ionosphere. We know that there appear the terminator times just around the sunrise and sunset in the diurnal variation of subionospheric VLF/LF signal (amplitude and phase). These terminator times a...

[1] The results presented in this paper provide an explanation for electromagnetic oscillations with frequencies much less than the fundamental eigenfrequency of the magnetosphere measured in the regions where the ionospheric conductivity is low and a small-amplitude, large-scale electric field in the ionosphere exists. This study is based on numerical simulations of a reduced two-fluid MHD mod...

Abeiraet-We have studied the extent to which certain transport processes affect ion composition and heat flow in the daytime, topside Venus ionosphere. Particular attention is given to the conditions that prevailed during the Mariner 5 measurements, at which time the topside Venus ionosphere appeared to be in a state of diffusive equilibrium. We have found that the ion composition is sensitive ...

[1] Data Interpolating Empirical Orthogonal Functions (DINEOFs) are a data-based method for determining a few orthogonal basis functions that optimally reproduce a given data set. This technique is applied to meridional drift measurements performed by the Coupled Ion Neutral Dynamics Investigation (CINDI) onboard the Communication/Navigation Outage Forecasting System (C/NOFS) as well as electro...

Solar radiations affect the total electron content of the ionosphere that may disturb the radio-frequencies used in telecommunications. It may state with full confidence that the increase in the critical frequencies of the F2 layer from the values observed in the morning hours to the afternoon maximum frequencies, is due to ultraviolet (UV) radiation from the Sun. During an ionospheric storm, s...

There is some intriguing research about whether large magnitude earthquakes are associated with ionospheric changes caused by electromagnetic signals released by the crushing of rock and their crystalline structures. If so then ionospheric changes might be a mechanism for major earthquake prediction. Prior to some recent quakes, scientists have detected electromagnetic and other disturbances in...

Apart from being used for plasma physics, the HF facility near Tromsø, Norway, can be used to perturb the ionosphere at various heights in different ways, thereby giving information about the ionosphere. The co-located incoherent scatter radars are probably the most powerful instrument for probing the ionosphere, but HF techniques can complement the radars and even have some advantages. The pri...

This paper describes the results of a preliminary study to determine the e€ective heating and cooling time constants of ionospheric currents in a simulated modulated HF heating, `beam painting' con®guration. It has been found that even and odd harmonics of the fundamental ELF wave used to amplitude modulate the HF heater are sourced from di€erent regions of the ionosphere which support signi®ca...