Worst-Case GPS Scintillations on the Ground Estimated from Radio Occultation Observations of FORMOSAT-3/COSMIC During 2007–2014
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The FORMOSAT-3/COSMIC (F3/C) satellite probes the S4 scintillation index profile of GPS signals by using the radio occultation (RO) technique. In this study, for practical use on the Earth’s surface, a method is developed to convert and integrate the probed RO S4 index, so obtaining the scintillation on the ground. To estimate the worst case, the maximum value on each profile probed by F3/C, which is termed S4max, is isolated. The isolated data are further used to construct the global three-dimensional distributions of S4max for various local times, seasons, solar activities, and locations. The converted S4max for the first time estimates the global distribution of ionospheric scintillations in the GPS L1 band C/A code signal on the ground. The results show that the worst-case scintillations appear within the low-latitude region of ±30°N, peaking around ±20°N magnetic latitude; they begin at 1900 MLT, reach their maximum at 2100 MLT, and vanish by about 0200–0300 MLT. The most pronounced low-latitude scintillation occurs over the South American and African sectors.
KeywordsFORMOSAT-3/COSMIC satellite Radio occultation Ionospheric scintillation S4 index
The authors thank Prof. Chao-Han Liu at Academia Sinica for useful comments and suggestions. The F3/C S4max data are retrieved from the COSMIC Data Analysis and Archival Center (CDAAC) and the Taiwan Analysis Center for COSMIC (TACC). Taiwan. This study has been partially supported by the project, MOST 103-2628-M-008-001, granted by Ministry of Science and Technology (MOST) to National Central University. The authors thank the Editor in Chief for his suggestions for editorial improvements.
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