## 1 Introduction  
A Swiss astronomer and mathematician, [PERSON], almost 170 years ago suggested that solar activity could influence the occurrence of earthquakes [1]. After the discovery of solar wind in 1959 [2], which has been an outstanding achievement in heliophysics and space physics, it has been recognized that solar wind plays a crucial role in the processes taking place in the Solar System and that it is the main factor that controls the terrestrial effects of space weather. For more than 60 years, much work has been done to reveal a lithosphere response to solar activity. As a result, it is assumed that, during substantial increases in solar wind activity, the Sun may be considered a significant agent provoking earthquakes [3]. More than five decades ago, it was revealed [4] that the maximum earthquake frequency occurs at times of moderately high and fluctuating solar activity. It was suggested that the coupling mechanisms that could trigger earthquakes could be abrupt accelerations in the Earth's angular velocity or surges of telluric currents in the Earth's crust [4]. The results in [5] showed that the perturbations in the atmospheric mass, which could be caused by solar activity, may affect the Earth's rotation and then influence earthquakes. Recently, a mathematical model [6] has been developed that considers a hypothesis of electromagnetic earthquakes triggered by a sharp rise of telluric currents in the lithosphere, including crust faults, due to the interaction of solar flare X-ray radiation with the ionosphere-atmosphere-lithosphere system. The model [6] suggested that the absorption of solar flare radiation in the ionosphere produces additional ionization in it,which results in the appearance of the additional electric current and electric field in the ionosphere, which will ultimately lead to an increase in the telluric current in the Earth's crust. The authors of [6] concluded that, after the solar flare of X-class, the telluric current density in the conductive layer of the lithosphere might reach \(10^{-8}\)-\(10^{-6}\) A/m\({}^{2}\), which is two to three orders more than the average telluric current density of 2\(\cdot 10^{-10}\) A/m\({}^{2}\) in the lithosphere. Also, they noticed that, calculated in [6], the parameters of telluric currents are comparable with the artificial electrical pulses injected into the Earth's crust in seismic-prone areas in Pamir and Northern Tien Shan [7] that resulted in the electromagnetic triggering of weak earthquakes and the spatiotemporal redistribution of the regional seismicity in these regions. What is a statistical result from the connection between solar and seismic activity, the more territories were analyzed, the more contradictory results appeared. Therefore, it was found in [8; 9; 10] that earthquakes occur frequently in the minima of solar activity, while, in [11; 12; 13], it was found that they occur frequently in solar maxima. For example, in [9], the data on earthquakes at different magnitude scales that occurred around the globe in 20-23 solar cycles (1963-2010) were compared with monthly sunspot numbers for the same time interval. They have found an out-of-phase relationship between earthquake counts and sunspot numbers. Also, they showed that the released seismic energy around the globe was picked up in years of solar minima. The same conclusion was made by [10], who investigated the relationship between secular variations in solar activity and seismic energy released on the planet in 1690-2002. However, an analysis of secular variations in solar activity and seismicity in the Mediterranean region revealed [11] that the highest seismic activity occurred around secular solar maximum. The authors of [12] studied worldwide earthquakes from 1600 to 2010 and revealed that earthquake counts mainly increase in the maxima of the solar cycle, but it depends on the tectonic plate location. They noted that tectonics is essential because there is heterogeneity in the crust, and the tectonic stress depends on each region.