Ionospheric absorption

About: Ionospheric absorption is a research topic. Over the lifetime, 1562 publications have been published within this topic receiving 20022 citations.

Estimation of ionospheric electric fields, ionospheric currents, and field-aligned currents from ground magnetic records

Abstract: An approximate method of separating the effects of ionospheric currents from those of field-aligned currents in ground magnetic perturbations observed in high latitudes is developed. The distribution of ionospheric electric fields can also be estimated. The procedure includes the following steps: (1) the calculation of the equivalent ionospheric current function on the basis of magnetic H and D component records on the earth's surface, (2) the computation of the electric potential distribution from the equivalent ionospheric current function by using a simple model of the ionospheric conductivity, (3) the derivation of ionospheric current vectors as well as electric fields and, (4) the derivation of the field-aligned current intensity by taking the divergence of the ionospheric currents. Several examples for both quiet and disturbed conditions are utilized to demonstrate how our method is successful in estimating the intensities of the electric fields and the ionospheric and field-aligned currents in the sense that the estimated values are in good agreement with those observed recently by radar and satellite methods. Significant portions of the H component in nightside auroral latitudes appear to result from the east-west ionospheric currents, called the auroral electrojets, while both the north-south ionospheric current and field-aligned current are almost equally important in producing the D component excursions. It is found that the ionospheric and field-aligned current distributions obtained are not very sensitive to the choice of the ionospheric conductivity model, unless the auroral enhancement is not given in an appropriate place. This indicates that even a simple conductivity distribution inferred from the distribution of the magnetic perturbations can make it possible to estimate the three-dimensional current system with a reasonable accuracy.

Nonlinear effects in the ionosphere

Abstract: The review is based in a report presented by the author at the RAS Physical Sciences Division's session in honor of Vitaly L Ginzburg's 90th birthday. It examines the current status of theoretical and experimental research on nonlinear phenomena arising when a powerful radio wave propagates in the ionosphere. The focus is on the modification of the ionosphere under the resonance excitation of natural plasma oscillations by radio waves. The upper-hybrid resonance gives rise to strong upper- and lower-hybrid plasma waves; excites strongly elongated ionospheric irregularities, and induces artificial ionospheric radio emission. Nonlinear processes are found to undergo complete transformation near double resonances, when the upper-hybrid frequency is close to a multiple of the electron gyromagnetic frequency. In the neighborhood of the Langmuir resonance, intense plasma waves and ion-sound waves are excited, electrons are effectively accelerated, and an artificial glow of the ionosphere appears.

Thermal Self-Focusing of Electromagnetic Waves in Plasmas

Abstract: An intense electromagnetic wave propagating in a collisional plasma is found to be unstable to a thermal self-focusing instability by a self-consistent solution of the hydrodynamic, heat conductivity, and wave propagation equations. The results are applied to ionospheric modifications and proposed power transmission experiments, and to laser-plasma interactions.