## 1 Introduction  
Ionospheric scintillation is one of the main concerns for satellite communications, in particular for Global Navigation Satellite Systems (GNSS) and low-frequency Earth observation missions, such as the upcoming P-band synthetic aperture radars and radar sounders. They may affect electromagnetic signals traversing the ionosphere, with rapid fluctuations in the intensity and/or phase of the signal. Several models [1] have been used in recent decades: [PERSON] (1973) [2, 3], [PERSON] (1985) [4], [PERSON] (1985) [5], [PERSON] et al. (2006) [6], the WBMOD climatological model [7], or GISM [8]. Besides being a problem for satellite communications and Earth observation missions, ionospheric scintillation can also be used as a tool for Earth observation. A novel technique, first introduced in [9], and continued in [10, 11], uses GNSS Reflectometry (GNSS-R) technology to infer ionospheric amplitude scintillation over oceanic regions. This technique allows the creation of ionospheric scintillation maps that could help the calibration and improvement of the currently available models. In the work presented here, the interaction between the ionosphere and the lithosphere is studied. The lithosphere is the solid, outermost shell of the Earth, and it is subjected to slow movements. The crust is divided in tectonic plates that can move relative to each other because they lie on top of the viscous, upper part of the mantle. The upper mantle plastic deformations absorb the displacements of the crust on timescales of thousands of years, but the solid crust deforms elastically leading to earthquakes through brittle failure. In the last decade, several studies revealed some coupling between the lithosphere, the atmosphere, and the ionosphere [12]. In this study, we will focus on the impact of the lithosphere on the ionosphere. According to [13; 14; 15; 16; 17; 18; 19], this coupling can be observed during earthquakes, in particular, before, during the so-called earthquake's preparation period, or immediately after them, with different physical explanations. When the ionospheric perturbations are observed before the earthquake, one reason for this is the perturbation of the background electric field by an electric potential appearing on the Earth's surface during the earthquake's preparation period [14]. For example, microfractures near the epicenter can generate positively charged holes that can diffuse to the surface, and generate these electric fields, that in the end, disturb the ionosphere. Furthermore, a thermal expansion of the atmosphere derived from the Land Surface Temperature (LST) increase prior to the earthquake occurrence, shown in several studies [15; 16; 17; 20], can generate a small gravity wave disturbing the electron density profile of the ionosphere, inducing changes in the TEC. The general interest in this field of study has increased in the last few years, as shown by the dedicated Chinese-Italian mission called China Seismo-Electromagnetic Satellite (CSES) to study the ionosphere-lithosphere coupling by monitoring electromagnetic and plasma density variations in the ionosphere. The satellite was launched to a 500-km altitude polar Sun-synchronous orbit in 2018, and it has already provided some interesting results of TEC variations related to several strong earthquakes in the Indonesian region [18]. Furthermore, some studies also detected ionospheric perturbations in the hours after large earthquakes, for example in the magnitude 9 Tohoku (Japan) earthquake in 2011. In this case, clear TEC deviations were measured following a concentric wave pattern around the epicenter [19]. Possible explanations for these perturbations are the acoustic waves generated by the sudden huge mass redistribution produced during the earthquake, that travel to the upper atmospheric layers or the ionosphere, inducing changes in the electron density. These waves can also be generated along the traveling Rayleigh waves propagating concentrically from the epicenter along the Earth's crust.