Characteristics and coupling mechanism of GPS ionospheric scintillation responses to the tropical cyclones in Australia

The ionospheric scintillation responses to tropical cyclones passing through the ocean near Australia, named as MARCUS in 2018, DEBBIE in 2017, MARCIA in 2015, and YASI in 2011, are investigated using GPS amplitude scintillation S4 index data collected from GPS stations of Ionospheric Scintillation Monitors installed in Darwin, Weipa, and Willis Island of Australia. Based on the data analysis in this study, some significant characteristics of GPS ionospheric scintillation responses to these tropical cyclones are identified as follows: (a) when the tropical cyclone centers are the closest to GPS stations of Ionospheric Scintillation Monitors with less than 500 km distance, more GPS ionospheric scintillations are observed and mostly concentrate above the tropical cyclone paths within 75°S–10.1°S geomagnetic latitude. (b) As a GPS satellite is passing through the tropical cyclone center, the S4 intensity of the GPS ionospheric scintillation is enhanced. (c) Frequency and intensity of GPS ionospheric scintillations are negatively correlated to the ellipsoid distances between GPS ionospheric scintillation observation stations of the Ionospheric Scintillation Monitors and the tropical cyclone centers. Regarding the coupling mechanism of GPS ionospheric scintillations and tropical cyclones, the electric field perturbations due to turbulent top movement from tropical cyclones might generate ionospheric irregularity and disturbance to produce bubbles. When GPS signals encounter these bubbles, GPS ionospheric scintillations occur.