International equatorial electrojet year : the African sector

International audienceThis paper presents the IEEY project in the African sector. The amount of our interpreted data is presently too short to allow proper scientific conclusions. Nevertheless, fist typical results illustrate our network possibilities. Some preliminary observations are briefly pre- , sented for their interest towards immediate research goals

The first real-time worldwide ionospheric predictions network: An advance in support of spaceborne experimentation, on-line model validation, and space weather

We report on the first realtime ionospheric predictions network and its capabilities to ingest a global database and forecast F-layer characteristics and "in situ" electron densities along the track of an orbiting spacecraft. A global network of ionosonde stations reported around-the-clock observations of F-region heights and densities, and an on-line library of models provided forecasting capabilities. Each model was tested against the incoming data; relative accuracies were intercompared to determine the best overall fit to the prevailing conditions; and the best-fit model was used to predict ionospheric conditions on an orbit-to-orbit basis for the 12-hour period following a twice-daily model test and validation procedure. It was found that the best-fit model often provided averaged (i.e., climatologically-based) accuracies better than 5% in predicting the heights and critical frequencies of the F-region peaks in the latitudinal domain of the TSS-1R flight path. There was a sharp contrast however, in model-measurement comparisons involving predictions of actual, unaveraged, along-track densities at the 295 km orbital altitude of TSS-1R In this case, extrema in the first-principle models varied by as much as an order of magnitude in density predictions, and the best-fit models were found to disagree with the "in situ" observations of Ne by as much as 140%. The discrepancies are interpreted as a manifestation of difficulties in accurately and self-consistently modeling the external controls of solar and magnetospheric inputs and the spatial and temporal variabilities in electric fields, thermospheric winds, plasmaspheric fluxes, and chemistry

On equatorial geophysics studies: a review on the IGIRGEA results during the last decade.

During the years 1993–1994, a continuous campaign of measurements has been held in the frame of the International Equatorial Electrojet Year (IEEY) with a network of 10 magneto-telluric stations and a network of three ionosondes. Other instruments have participated during shorter periods, HF radar and optical Fabry-Perot 630 nm interferometer.After the IEEY campaigns, the International Group of Research in Geophysics in Europe Africa (IGRGEA created in January 1995), has organized the research in geophysics. This paper report the main results of the IGRGEA during the last decade at local, regional and planetary scales.At a local scale, the HF radar data highlighted the complex structure of echoes in the equatorial zone and allowed to explain the “necklace” echoes as due to oblique propagation into the type I instability levels. This radar observed atmospheric storm electric field discharges at Es layer for the daytime and Equatorial Spread F at night-time. A series of original results concern Doppler spectra and the electric field change on plasma drifts across the ionosphere, gravity waves effects as well the ESF multi-process sources.At a regional scale, magnetic data were used to parametrize the Equatorial Electrojet (EEJ). Ionospheric data, magnetic data and UARS satellite were brought together as input parameters of the Richmond's EEJ model to reproduce the EEJ and the magnetic field variations associated to EEJ. The comparisons between magnetic data, and the magnetic field computed from the physical model and from the parametrization of the EEJ are all in good agreement. Ionosonde data were included in the IRI. Ionosonde data revealed the field aligned f0F2 crests of ionization at mid morning and early afternoon hours. Measurements of equatorial night-time wind variations, obtained for the first time over African equatorial zone with the Fabry-Perot interferometer, shown the strong variability of atmospheric winds.At a planetary scale, the parametrization of the EEJ was done using the magnetometers chain involved during IEEY in the three longitude sectors. Finally, we present the results on electrodynamic coupling between high and low latitudes with overshielding or shielding events