A comprehensive comparison between the TOPEX/Jason and GPS TEC observations

Abstract

The TEC data obtained from the TOPEX/Jason and GPS satellites have provided an unprecedented global view of the ionosphere and utilized for various studies on both the weather and climate of the ionosphere. However there are fundamental differences between the two data sets: the TOPEX/Jason TEC observations are performed only over the global ocean while the GPS TEC data are based on the ground stations that are mostly distributed over the global continents. Another important difference is that the orbital altitudes of the satellites are very different. The TOPEX/Jason satellites are orbiting at about 1330 km altitude, an approximate boundary between the topside ionosphere and plasmasphere at mid-latitudes. The GPS satellites circle around the Earth at much higher altitude of about 20,200 km, which includes not only the ionosphere but also significant part of the plasmasphere at low and middle latitudes. These discrepancies become a challenge when the two data sets are combined for the climatological studies of the ionosphere and the plasmasphere. For the ionospheric study, the difference in the spatial coverage makes them perfect data sets to be combined, but the altitude difference hinders this type of use. For the study of the plasmasphere, on the other hand, the difference in the altitudes provides an excellent opportunity to study the plasamaspheric electron densities in which there are little observations, but direct estimations of the electron densities from the TEC differences are not straightforward due to little spatial overlap between the two. A comprehensive comparison between two data sets will be performed in order to challenge the difficulties described and the preliminary results of the study will be presented.