The ionospheric weather of S4 scintillation probed by FORMOSAT-3/COSMIC during 2007-2014

FORMOSAT-3/COSMIC (F3/C) probes the S4 index profile of GPS signal by using radio occultation (RO) technique. For practical use on the earth's surface, a method is developed to convert and integrate the probed RO S4 index 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 3 dimensional distributions of S4max in various local times, seasons, solar activities, and locations. The converted S4max for the first time estimates the global distribution of ionospheric scintillation in GPS L1 band C/A code signal on the ground. Results show that the worst-case scintillations appear within the low latitude of 30-degree, peaking around 20-degree, magnetic latitude, 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-African sector.