Global observations of L band scintillation at solar minimum made by COSMIC

We report observations of the L band scintillation climatology made during the minimum of solar cycle 23/24 using the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC, also known as FORMOSAT-3). The measurements of the S4 scintillation index were made using the GPS Occultation Experiment instrument, which is a dual-frequency GPS receiver used for routine ionospheric measurements via occultation of satellites in the GPS constellation. A method for geolocating the S4 measurements is presented and discussed. The geolocated COSMIC measurements are used to construct monthly climatologies of the S4 scintillation index, which are in good agreement with previous climatologies based on ground-based measurements. COSMIC measurements of the electron density and S4 index permit an assessment of the correlation of the S4 index with the electron density. The scintillation climatology for March and April 2007 is compared to the coincident monthly climatology of the electron density, and a correlation is observed, but this correlation does not appear to hold globally. The COSMIC measurements are shown to be a powerful data set for studying L band scintillation and its correlation with the underlying ionospheric morphology.