###### Abstract  
In this study, a multi-station and multi-instrument system, organized and proposed for ionospheric scintillation and equatorial spread-F (ESF) specification and their associated motions in the Taiwan-Philippines sector, is outlined. The issues related to the scintillation and ESF event observed on 26 October 2021, at magnetic quiet conditions are presented and discussed. We first indicate the existence of a plasma bubble in the Taiwan-Philippines sector by using the FormoSat-7/Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (FS7/COSMIC2) GPS/GLONASS radio occultation observations. We verify the latitudinal extent of the tracked plasma bubble using the recorded ionograms from the Vertical Incidence Pulsed Ionospheric Radar located at Hualien, Taiwan. 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 133 ground-based receivers located in Taiwan and the surrounding islands. We also operate two high-sampling, software-defined GPS receivers and characterize the targeted plasma irregularities by carrying out spectrum analyses of the received signal. As a result, the derived plasma irregularities moved eastward and northward. Furthermore, the smaller the irregularity scale, the higher the spectral index and the stronger the scintillation intensity were at lower latitudes on the aimed irregularity feature. equatorial and low-latitude ionosphere; ionospheric irregularity; scintillation; radio occultation observation; COSMIC; ionogram; GPS/GNSS 2022142931  
pre-reversal enhancement (PRE), generally at F-region heights [5; 8; 9]. As a result, the ionosphere moves upward, develops steep density gradients and large-scale plasma depletions in the bottom side F-region, and becomes unstable, triggering the Rayleigh-Taylor (R-T) instability. The plasma depletions, called plasma bubbles, become populated with mesoscale or small-scale irregularities and rise to great heights. These plasma bubbles, extended in altitude, also map out along magnetic field lines to the north and south of the magnetic equator, i.e., higher magnetic latitudes. These structured irregularities generally move eastward by the action of a vertical oriented polarization electric field. Undergoing a non-linear cascade process of electric field driving and wave-wave coupling [10], irregular structures drift and vary from large- to small-scale. The spectral distribution of irregularities includes a broad component associated with waves. Equatorial spread-F (ESF) thus stems from high-frequency radar observations of the \"spread\" of the ionospheric echoes in ionograms and can be used to describe equatorial and low-latitude F-region instability phenomena. Scintillation and ESF activities attain a maximum value during high sunspot activity periods, especially during equinoxes (March, April, September, and October), owing to the increased value of the background ionization density [11]. In particular, low-latitude scintillation can be dictated by solar transients, such as magnetic storms [11]. Several techniques have been used to observe and study ionospheric irregularities and scintillations. These include sounder, radar backscatter, in-situ measurements onboard rockets or satellites, ground-based satellite beacon signal observations, space-based navigation beacon observations using radio occultation (RO) techniques, etc. Earlier investigations [12] developed an operational system, named the SCIntillation Network Decision Aid (SCINDA), to nowcast and forecast scintillation. At the operator terminal, the SCINDA data were combined with an empirical plasma bubble model to generate three-dimensional maps of irregularity structures and two-dimensional outage maps for the equatorial region in the American sector. In this study, another multi-station and multi-instrument system, developed for ionospheric scintillation and ESF specification in the Taiwan-Philippines sector, is outlined.