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Colloquium
Scintillation Theories and Remote Sensing of Ionospheric Irregularities using Electromagnetic Waves

Abstract

Accurate and precise specification and characterization of the ionospheric electron density (N_e) irregularities are important to radio sky-wave communications and satellite navigation. In this scenario, multi-instruction and multi-station systems have been developed and/or organized for ionospheric irregularity and scintillation observations in the Taiwan-Philippines sector. The theoretical simulations show that both scintillation index S4 and S2 values become saturation when a sampling spatial scale is less than the first Fresnel zone (FFZ), and S_4 and S_2 values could be underestimated and be approximately proportional to the logarithm of sampling spatial wave numbers up to the FFZ wave number. We could indicate the existences of plasma bubble and/or sporadic-E (Es) in the Taiwan-Philippines sector using the FS3/COSMIC or FS7/COSMIC2 GPS/GLONASS radio occultation (RO) observations. We verify the latitudinal extent of the tracked plasma bubble or Es using the recorded ionograms from the Vertical Incidence Pulsed Ionospheric Radar (VIPIR) systems located at Hualien and Longquan, Taiwan, etc. We further discuss the spatial and temporal variabilities of two-dimensional vertical scintillation index VS_4 maps based on the simultaneous GPS L1-band signal measurements from more than 130 ground-based receivers located in Taiwan and the surrounding islands. We also operate several high-sampling software-defined GPS receivers and characterize the targeted plasma irregularities by carrying out spectrum analyses of the received signal. Generally, the F-layer scintillation and Es-layer event climatology, namely, its variations with each identified zone, altitude, season, and local time have been documented.