High latitude ionospheric irregularity detection using COSMIC radio occultation observations

High latitude ionospheric scintillations is a concern for satellite-based navigation system. This paper analyzes electron density distributions in the high latitude disturbed ionosphere using COSMIC radio occultation (RO) observations. Analyses are based on the COSMIC level 2 product: retrieved ionosphere electron density. A polynomial approximation is used to filter the vertical electron density profiles and identify ionospheric disturbances of high frequency. Electron density profiles and their fluctuations provide new information on the spatial variations and altitude distributions of different scales of structures in the ionosphere. Average electron density maps for high latitudes are also generated as a function of altitude and latitude for local night sectors using COSMIC RO observations. A geomagnetically disturbed day and a quiet day are picked for comparison. Typical radio occultation (RO) events are selected for validation. Results of the polynomial filter provide the altitude distribution and intensity information of ionospheric instability structures. Correlation with analysis done by wavelet powerspectrum of electron density is also conducted. It is determined that the presence of auroral and/or polar cap ionospheric irregularities can be detected using COSMIC RO observations. Such irregularities can cause significant scintillation effects for Global Navigation Satellite Systems (GNSS). COSMIC is a powerful tool for practical applications in GNSS space weather monitoring.