Total electron content and scintillation studies – Current status

277-295Satellite beacon studies have contributed mainly in two areas of research, namely, total electron 'content (TEC) and small scale structures or irregularities, and both of these have important practical implications in trans-ionospheric radio propagation. The current status of these two fields of research is summarized, and recent developments in the study of equatorial anomaly using US NNSS satellite signals, geomagnetic storm effects, travelling ionospheric disturbances, nighttime enhancements, and slab thickness, which are of particular relevance to the equatorial and low latitudes, are reviewed. Recent initiatives on TEC modelling and comparison of existing models with observations are highlighted. New concepts like computerized ionospheric tomography are briefly outlined. Recent advances in the understanding of scintillation morphology, particularly its longitude dependence and the variation of the width of the equatorial scintillation belt are summarized. Future directions in respect of multitechnique investigation of the low latitude ionosphere and the mosphere, measurement of GHz scintillations, and spectral studies are pointed out. Important application areas of this field are also included