Self-focusing of electromagnetic beams in the ionosphere considering Earth's magnetic field

Abstract

In this paper the focusing/defocusing of (i) a single Gaussian electromagnetic beam and (ii) a number of coaxial Gaussian electromagnetic beams, propagating in the extraordinary mode along the Earth's magnetic field in the ionosphere has been investigated in the paraxial approximation. The growth of a sinusoidal instability on account of self-focusing has also been studied. The nonlinearity in the dielectric function, responsible for the focusing/defocusing arises from the redistribution of the electron density, caused by the non-uniform distribution of the electron temperature. The electron temperature is determined by the energy balance for electrons/ions taking into account the Ohmic heating, the collisions and the radiation from the sun. The wave frequency has been assumed to be greater than the plasma frequency. The electron cyclotron frequency due to the Earth's magnetic field in the ionosphere is much larger than the electron collision frequency. This is specifically true for a height of 150 km. Numerical results have been presented for a range of parameters and a discussion of the same has been presented.

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.…”

Relativistic cross-focusing of extraordinary and ordinary modes in a magnetoactive plasma

“…Some authors (Sinha and Sodha 1980) have analyzed the selffocusing of an electromagnetic beam in a magnetized plasma on a short time scale, when the ponderomotive nonlinearity is dominant, and on a long time scale, when collisional nonlinearity is dominant. The simultaneous focusing of two coaxial beams and the cross-focusing of the ordinary and extraordinary modes in a magnetized plasma have also been studied (Sodha and Sharma 2007;Sodha and Sharma 2008). An important consequence of the study of self-focusing was the prediction of the penetration of an electromagnetic beam in the overdense magnetized plasma.…”

Focusing of a dark hollow Gaussian electromagnetic beam in a magnetoplasma

“…In recent investigations Sodha et al [24] have developed a theory of self focusing, considering the conduction by both the ionic and the electronic species as well as collisions, in a fully ionized collisional magnetoplasma, while Sharma et al [25] have analyzed the three characteristic regimes for propagation of an electromagnetic beam in a magnetoplasma. Further, Sodha and Sharma [26] have applied the theory of self focusing to the ionosphere, taking the Earth's magnetic field into account.…”