Latitudinal and temporal variation of equatorial ionospheric irregularities determined from GPS scintillation observations

摘要

In this paper we investigate the spatial and temporal distribution ofionospheric irregularities in the South-East Asian longitude sector byanalysing the scintillation of GPS signals received at ground based stations.The data used for this work were collected during 1998 to 2002 with our regionalnetwork of GPS based scintillation monitors (Thomas et al., 2001).The aim of this analysis is to better understand the morphology and climatologyof ionospheric irregularities in our region. Interesting differences between thenorth and south anomalies are noted when we examine the latitudinal–temporalvariation of irregularity activity. We investigate the possible causes of thesedifferences and note that variations in the irregularity seeding mechanismand in the background ionosphere at the two anomalies could be important.Phase screen diffraction theory is used to analyse our scintillation data andwe note problems with this theory for ray-paths with large off-zenithangles. The height of the phase screen is another important issue. We discussthe implications for models which rely on phase screen diffraction theory.