Spectra of equatorial total electron content derived from GPS signals
Abstract. High cadence GPS TEC signals collected on Ascension Island, South Atlantic Ocean, during sunspot minimum, and in Vanimo, Papua New Guinea, over half a solar cycle, have been analysed for their spectral properties. A new parameter Tk has been introduced to quantify the strength of TEC irregularities at a scale size of 1 km. The scintillation strength and the spectral index have been analysed as functions of each other, and of local time, season, location and sunspot number. The scintillation strength is highest in autumn and spring in both locations, although the quietest period is summer in Ascension and winter in Vanimo. The scintillation strength decreases with decreasing sunspot number, but is consistently lower in Vanimo than in Ascension. The spectral index decreases with scintillation strength, and increases during the hours of the evening. A method is developed to estimate Tk from the large data base of S4 measurements.