## 1 Introduction
They revealed that, in the 11-year solar cycle, two maxima in the number of earthquakes appear--one in the sunspot maximum and another one in the descending phase of the solar cycle. As for the association of strong (M \(\geq\) 7.0) earthquakes with the descending phase of solar activity in the 11-year solar cycle, Reference [24] (pp. 18-19, Figures 10 and 11 and Table 1) systematized the results, showing that this effect was most pronounced for those earthquakes that occurred at the footprint of geomagnetic lines L = 2.0-2.2 in the Earth's crust (Figure 1). The region 2 \(\leq\) L \(\leq\) 3 is known as the electron slot. Let us remember that L is the geocentric distance in the Earth's radii at which a dipole magnetic field line crosses the magnetic equatorial plane. As summarized in [25], the slot is a transition region between the outer and the inner radiation zones, often relatively devoid of energetic electrons. However, during strong geomagnetic storms, this gap can be filled to a large degree by moderate  
Figure 1: The monthly sunspot numbers (curve) and dates of strong (M \(\geq\) 7.0) earthquakes (arrows) that occurred in 1973–2014 at the footprint of L = 2.0 to 2.2 geomagnetic lines from [24] (their Figure 11). (and even high)-energy electrons. For example, in the intense \"Halloween\" storm of late October-early November 2003, the slot region was filled with multi-MeV electrons for several weeks. Thus, the slot region can present several space weather concerns, including low- and medium-energy electron enhancements, multi-MeV electrons, and intense solar energetic particle events [25]. In this regard, the result in Figure 1 gives us a hint that the mediator in the occurrence of shown earthquakes could be geomagnetic lines populated by charged particles and, therefore, highly conductive. Such an assumption is supported by the mathematical model in [6], in which the conductivity of the medium plays a vital role in the electromagnetic generation of earthquakes. Also, it is supported by the results of [26], where the seismic activity was analyzed after four geomagnetic storms accompanied by the precipitation of relativistic electrons from the outer radiation belt into the lower magnetosphere, where they formed additional radiation belts (storage rings) around particular geomagnetic lines. It was revealed, for example, that, after a giant \"Halloween\" storm (Dst = \(-\)383 nT), which was followed by filling a slot region with relativistic electrons for about 50 days [27] (their Figure 1), a strong M = 7.8 earthquake occurred at the Aleutian Islands on 17 November 2003, near a footprint L\(\sim\)2.1 with a time delay \(\sim\)19 days. These results suggest that some earthquakes may be looked at as addressed (targeted), since they may occur near the footprint of particular (addressed) geomagnetic lines that were filled by charged particles and became conductive. In the magnetosphere, there are two places where the solar wind-charged particles can fill the geomagnetic lines; these are the areas of the northern and southern polar cusps. In Figure 2, the Earth's magnetosphere with two polar cusps is schematically presented. The boundary that separates the solar wind area, known as a magnetosheath, from the magnetosphere is called the magnetopause (outer boundary of the Earth's magnetic field). Solar wind energy enters from the magnetosheath to the magnetosphere due to a process of magnetic reconnection [28]. When magnetic reconnection occurs at the magnetopause, the solar wind particles from the magnetosheath move continuously along the opened geomagnetic lines into the cusp and magnetotail [29]. The cusps (yellow dots in Figure 2), first observed by [30; 31], are the magnetosphere regions filled with the denser plasma. The cusp is a funnel-shaped region in which, from a magnetic field point of view, the compressed high-latitude dayside geomagnetic field lines and the elongated nightside geomagnetic field lines converge toward the geomagnetic poles [32].