Daily Global Plasmaspheric Maps Derived From COSMIC GPS Observations

GPS precise orbit determination antenna observations from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites represent a new plasmaspheric data source, which are globally distributed and continuously available. By assuming that all free electrons in the plasmasphere at an altitude range of approximately 800-20 200 km are contained in a thin shell (namely, a single-layer model), daily global plasmaspheric maps (GPMs) of plasmaspheric electron content (PEC) are constructed using a spherical harmonic expansion. We employ this method to obtain PEC maps for DOY 102-131 in 2008 and compare the PEC model values with the Meteorological Operational satellite programme (MetOp) measurements. According to the estimation results, the global PEC values show features that are consistent with previous studies and exhibit higher estimation accuracy; the estimation results of COSMIC GPS receiver differential code biases also agree well with the reference values in the 30 days. During this period, the mean rms of the differences between MetOp PEC measurements and GPM PEC values is 1.29 TECU, which suggests that GPMs can offer reasonable and high-precision PEC values.