## 1 Introduction  
The idea that space weather--as measured by sunspots, cosmic rays, solar wind, interplanetary magnetic fields, geomagnetic activity, and precipitation of charged particles from the radiation belt--may play a role in triggering earthquakes has a long history but has not received physical justification for the time being. It was noted in [1] that the problem's difficulty is that the unknown is a physical mechanism of action involving relatively weak fields of cosmic origin on tectonic processes. The authors of [2] suggested that geomagnetic variations affect rocks, e.g., by inducing eddy currents in the Earth's crust via an alternating magnetic field, leading to rocks' additional heating. They modeled the distribution of heat flows generated by 98 magnetic storms on the surface and in the interior of the Northern Tien Shan. They showed that the average amount of energy released in the Earth in the form of heat is about \(7.4\times 10^{11}\) J, which is comparable to the amount of energy released in this territory over the same time interval. Simultaneously, they noted that the heat flow transferred by storms into the ground is 2-3 orders of magnitude lower than the heat flow from the ground and, therefore, cannot play a significant role in the earthquake preparation phase but can most likely accelerate the process of releasing the accumulated tectonic stress if it has already started. It was also assumed that the action could be forceful, owing to the movement of telluric currents in the Earth's magnetic field. However, [3] showed that these ponderomotive forces produce only the weakest stresses and deformations in the Earth's crust. As the authors of [4; 5] suggested, the Alfven waves, which can drive currents in the ionosphere and reradiate the energy as electromagnetic waves that propagate to the ground [6], could mediate between space weather and seismic activity. Over the last 30 years, international community cooperation has suggested the concept of the lithosphere-atmosphere-ionosphere coupling (LAIC), which indicates that electromagnetic disturbances in the lithosphere accompany the earthquake preparation process and can modify the electric field in the global electric circuit (GEC) (see [7; 8; 9; 10; 11] and references herein). The GEC links the electric fields and currents flowing in different parts of the atmosphere [12; 13]. There are three main generators of fields and currents in the global electric circuit [13]: (1) the troposphere generator (continuous thunderstorm activity of the Earth, with about 46 lightning strikes per second); (2) the ionospheric wind dynamo; and (3) the solar wind/magnetosphere dynamo. The troposphere generator may provide a 200 kV to 600 kV potential difference between the ground and the ionosphere. The ionosphere generator (ionospheric wind dynamo) may provide about 5 kV to 15 kV of potential difference between the high and low latitudes. The magnetospheric generator (solar wind/magnetospheric dynamo) can provide a potential drop of 40 kV to 130 kV across the polar cap. Thunderstorms in the troposphere are the strongest source of voltages/currents in this circuit. The electric current flows upward from the thunderstorm areas and spreads out all over the globe through the ionosphere and through the magnetosphere along magnetic field lines to the opposite hemisphere. The current returns to the surface of the Earth as the fair-weather troposphere-to-Earth current. The density of the vertical electric conduction current in the GEC depends on conductivity and is about \(10^{-12}\) A/m\({}^{2}\) on average. The LAIC concept considers that radon emanation may accompany an earthquake preparation process [7]. The radon concentration shows relatively strong spatial variation and differs widely above continental and oceanic areas.