Estimation of plasmaspheric electron content at low latitudes using GNSS signals

Abstract

The ionosphere (approx. 50 to 1000 Km) and Plasmasphere (approx. 1000-20, 500 Km) are the two ionized regions. These regions are dispersive in nature and introduce path delay proportional to Total Electron Content (TEC) on the propagating L-Band Global Navigation Satellite System (GNSS) signals. Because of this dispersive nature, a dual frequency GNSS receiver is used to estimate the time delay effects on the propagating signals. Though the plasmasphere's electron density is several orders of magnitude less than that of ionosphere, plasmasphere has a significant effect on the propagating signals. This is due to longer propagation path of the GNSS signals in plasmasphere. Therefore, the frequency dependent path delay is proportional to the combination of both ionospheric electron content (IEC) and plasmaspheric electron content (PEC). Any GNSS receiver at a particular geographic location has its own geometry with the visible satellites. Thus, the contribution of PEC to GNSS-TEC varies accordingly. It has been reported that, the ionization contribution of plasmasphere over Japan ranges from 12% to 60% and at equatorial latitudes it is approximately 30%. But at low latitudes stations like India very limited work has been done. Therefore an attempt is made using GNSS data and IRI model to estimate PEC.