## 1 Introduction  
Today's society relies more and more on Global Navigation Satellite Systems (GNSSs) and satellite-to-Earth communications in a wide range of industries and critical systems. The important threats for the GNSS and satellite communications are the ionospheric plasma gradients and corresponding signal scintillations. Such ionosphere-related signal scintillations are rapid fluctuations in the amplitude, phase, and angle of propagated radio signals due to the presence of ionospheric irregularities and plasma density gradients that the radio signals traverse. Scintillations occur at a broad range of frequencies. L-Band scintillation adversely impacts on the trans-ionospheric communications, as well as on the continuous tracking of GNSS signals for position, navigation, and timing services [1, 2, 3, 4, 5, 6]. The most severe ionospheric plasma irregularities and scintillations occur primarily in the low-latitude region [7, 8, 9, 10], and, here, they are associated with the development of equatorial plasma bubbles [11, 12, 13, 10]. The plasma irregularities at mid- and high latitudes are mainly related to space weather, specifically how the ionosphere responds to the geomagnetic disturbances [14, 15]. During geomagnetic storms, the energy input coming from the magnetosphere-ionosphere interaction in the form of enhanced electric fields, currents, and energetic particle precipitation perturbs the ionosphere through high-latitude ionization, Joule and particle heating, ion-drag forcing, and disturbed electric fields, resulting in ionospheric irregularities and strong plasma density gradients and enhancements [16; 17; 18]. The fact is that ionospheric irregularities possess a wide range of spatial and temporal scales and occur at different geographical locations [18]. Ionospheric irregularities are detected and studied mainly by two techniques: direct in situ measurements of plasma density by satellites and remote sensing based on radio wave propagation. The in situ plasma density observations onboard different satellite missions (e.g., [PERSON] et al. [19] and [PERSON] et al. [20] with DMSP operated at \(\sim\)840 km altitude, [PERSON] et al. [21] and [PERSON] and Groves [22] with C/NOFS at 400-850 km orbit altitude, [PERSON] et al. [23] with ROCSAT-1 at 300-400 km orbit altitude, [PERSON] et al. [24] with CHAMP at 300-400 km orbit altitude, and [PERSON] et al. [25] with Swarm constellation at \(\sim\)500 km orbit altitude) were used to detect plasma density variations along the satellite orbits. From these measurements, statistical parameters for equatorial plasma bubble occurrence, responsible for plasma density gradients, were derived. Recently, [PERSON] et al. [26] presented an approach for identifying the ionospheric plasma density irregularities form the Ion Velocity Meter (IVM) in situ plasma density observations onboard the new COSMIC-2 mission. Here, the detected irregularities related with the equatorial plasma bubble development were geolocated on the satellite orbit planes, with further construction of the global maps of the plasma bubble locations based on the initial detection of IVM irregularities. The major limitation of the satellite in situ measurements is that these data represent a one-dimensional horizontal cut of the ionosphere at a fixed altitude. So, the detection of ionospheric irregularities strongly depends on whether these structures have already reached the satellite orbit altitude or not. The ground-based GNSS observations are successfully used to characterize the occurrence of ionospheric plasma irregularities and their intensity by the ROT (rate of change of total electron content (TEC)) and ROTI (ROT index) [27; 28]. Based on the results reported in [28; 29; 30], it was concluded that the ROTI could be also effectively used as a proxy for assessing the presence of amplitude scintillations.