Multi-instrument and multi-station observations and predictions of low- and mid-latitude ionospheric irregularities

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Significant ionospheric irregularities, e.g. equatorial plasma bubbles (EPB), could be induced by enhanced eastward electric field, called pre-reversal enhancement (PRE), or atmospheric gravity wave. Such ionospheric irregularities could induce radio scintillations which cause signal loss and/or phase cycle slips in receiving trans-ionospheric radio wave. In this scenario, multi-instruction and multi-station systems are proposed to be organized and/or developed for ionospheric scintillation and equatorial spread-F (ESF) specification and prediction of irregularity occurrence in the low- and mid-latitude regions. We first indicate the existence of a plasma bubble using the FS7/COSMIC2 GPS/GLONASS radio occultation (RO) observations. We verify the latitudinal extent of the tracked plasma bubble using the recorded ionograms from the Vertical Incidence Pulsed Ionospheric Radar (VIPIR) network located in the east-Asia area. We further discuss the spatial and temporal variabilities of two-dimensional vertical scintillation index VS4 maps based on the simultaneous GPS L1-band signal measurements from more than 130 ground-based receivers located in Taiwan. We also operate more than four high-sampling software-defined GPS&SBAS receivers in Taiwan and a small-scale high-rate GNSS network in Ethiopia and characterize the targeted plasma irregularities by carrying out spectrum analyses of the received signal. Furthermore, we suggest that a post sunset decrement on the virtual heights of fixed-frequency ionospheric echoes could be a good precursor for post sunset scintillation and ESF events. Such features can be used for correlation analysis with plasma drifts retrieved by the International Reference Ionosphere (IRI) and gravity wave activity retrieved from TIMED/SABER satellite measurements, and, as a result, a prediction model is expected to be accompanied. This study will address new objectives and results of denser GNSS RO observations from the FS7/COSMIC2 and joint ground-based observations from GPS/GNSS receivers and ionospheric remote sensing radar to accurately structure and model the Earth’s low- and mid-latitude ionospheric irregularity. All proposed objectives are summarized below: (1) identify EPB using FS7/COSMIC2 GNSS RO observations and the VIPIR network, (2) determine global large-scale and regional meso- or small-scale EPB distributions using FS7/COSMIC2 and ground-based GNSS network, respectively, (3) characterize ionospheric irregularity intensity, scale and movement using high-sampling GNSS receivers, and (4) model and predict EPB occurrence based on correlation analysis with plasma drift and gravity wave activity parameters.