Self‐focusing of an electromagnetic pulse in the ionosphere

Abstract

[1] In this paper, the self-focusing of electromagnetic pulsed beams having Gaussian and sine profiles in the ionosphere have been studied. The self-focusing of an electromagnetic pulse is caused by the nonlinearity in the dielectric function caused by the nonuniform distribution of electron temperature, determined by the Ohmic heating, solar radiation and energy loss in collisions with ions and neutrals. The radial distribution of the electron temperature causes a radial distribution of electron density and thereby that of the refractive index, which causes self-focusing. The wave frequency has been assumed to be much larger than the electron collision frequency, and the temperature of the ions has been assumed to be equal to the temperature of neutrals; this assumption is justified in the ionosphere up to a height of 400 km. In the analysis, the electromagnetic wave equation and the energy balance equation has been solved simultaneously to obtain ordinary differential equations governing the beam width parameter and the electron temperature (on and away from the axis), respectively, in the paraxial approximation. For computations, the database for the midlatitude daytime ionosphere at the height of 150 km, compiled by Gurevich (1978), has been used. The transient behavior of the electron temperature (on and away from the axis) has been graphically presented for different values of pulse widths. The dependence of the beam width parameter on the distance of propagation for different times of retardation has also been plotted and discussed.

Theoretical analysis for transmission of Gaussian and sine time irradiance of electromagnetic beam in collisional dusty plasmas

“…Sodha et al [31] also analysed the cases of thermionic emission, photoemission, and emissionless processes to formulate the problem of fluctuation of charge on account of presence of dust grains. Several investigations on temporal profile of electromagnetic wave propagating in dust-free plasma have been carried out by various researchers [32][33][34] but in this paper; analytical model is evolved to access the transmission kinetics of both Gaussian and Sine time irradiance of electromagnetic wave owing to mutual interactions of dust and other plasma components. It is familiar that the electrons in dusty plasma get heated up because of highly irradiated electromagnetic wave to the stationary state temperature of the order of relaxation time '= 1/( comp ef ) , where comp is the fractional loss of energy of electrons due to collisions and ef is the effective collision frequency under the influence of dust grains.…”

Distortion of an amplitude modulated electromagnetic signal with time-dependent dust charging

“…Transient and time-periodic self-focusing of a laser beam has been a fascinating field of research for many-many years [1][2][3][4][5][6][7].…”