Electromagnetic Coupling of Geospheres: 1. Disturbances in the Lower Ionosphere

The relevance of this study stems from the fact that, to date, there is no reliable and detailed explanation of the electromagnetic mechanism governing interactions between subsystems within the Earth (inner shells)-atmosphere-ionosphere-magnetosphere (EAIM) system. This mechanism can manifest itself under the action of high-energy sources of both natural and anthropogenic origins. Natural sources include weather fronts, thunderstorms, hurricanes (typhoons), volcanic eruptions, earthquakes, etc. All these natural processes may generate intense electromagnetic radiation in the VLF range (3-30 kHz). Such radiation is capable of interacting with the plasma in the lower ionosphere, triggering a series of secondary geophysical processes. This study presents the findings on the electromagnetic mechanism of subsystem interactions within the EAIM system, specifically focusing on the impact of intense electromagnetic radiation on the parameters of the lower ionosphere. A single lightning strike during the daytime can increase electron temperature by a factor of 60-44 at altitudes of 60-80 km, respectively. At night, a significant increase in electron temperature (by a factor of 60-50) can occur at altitudes of 80-95 km, respectively. This substantial electron heating results in the transparentization effect of the lower ionosphere plasma, leading to reduced electromagnetic radiation absorption at altitudes up to 80 km during the day. At night, however, the plasma exhibits a saturation effect at altitudes of 80-100 km, which is accompanied by an increase in electromagnetic radiation absorption. A single lightning strike does not cause a noticeable disturbance in electron density or the intensity of its fluctuations. However, it can produce minor (similar to 0.01 nT) perturbations in the geomagnetic field and significant (similar to 1 V/m) spikes in the vortex electric field. At a sufficiently high lightning frequency, noticeable disturbances in electron density and the intensity of its fluctuations may occur, potentially leading to the accumulation of disturbances N and (Delta N-2) over bar. Significant perturbations in the parameters of the lower ionosphere can, in turn, generate secondary effects that propagate into the magnetosphere and magnetically conjugate regions.