Basic Theoretical Methods in Microwave Plasma Polarimetry: Quasi-Isotropic Approximation, Stokes Vector Formalism and Complex Polarization Angle Method

AbstractThe equation for evolution of the complex amplitudes ratio (CAR) ζ = Ey/Ex in weakly anisotropic inhomogeneous media is derived on the basis of quasi-isotropic approximation (QIA) of the geometrical optics method. This equation is convenient for the description of electromagnetic wave polarization in magnetized plasma of thermonuclear reactors like the ITER. The equation for the CAR is in agreement with other approaches, analyzing polarization evolution in weakly anisotropic media, in particular, with the equation for complex polarization angle and, via QIA equations, with the Segre equation for Stokes vector evolution. Simple analytical solutions for the CAR, which relates to normal mode propagation in homogeneous and weakly inhomogeneous plasma, are obtained. Besides, the equation for the CAR is solved numerically to describe the phenomenon of normal wave conversion in magnetized plasma in the vicinity of the orthogonality point between the ray and the static magnetic field. In distinction to the line-averaged measurements in traditional plasma polarimetry, the phenomenon of normal wave conversion opens the way for measuring the local plasma parameters near the orthogonality point.

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Evolution of the polarization of electromagnetic waves in weakly anisotropic inhomogeneous media — a comparison of quasi-isotropic approximations of the geometrical optics method and the Stokes vector formalism

Open Physics ◽

10.2478/s11534-008-0044-y ◽

2008 ◽

Vol 6 (3) ◽

Cited By ~ 2

Author(s):

Yury Kravtsov ◽

Bohdan Bieg

Keyword(s):

Electromagnetic Field ◽

Electromagnetic Waves ◽

Normal Modes ◽

Geometrical Optics ◽

Inhomogeneous Media ◽

Stokes Vector ◽

Coupled Equations ◽

Isotropic Approximation ◽

Total Phase ◽

Electromagnetic Beams

AbstractThe main methods describing polarization of electromagnetic waves in weakly anisotropic inhomogeneous media are reviewed: the quasi-isotropic approximation (QIA) of geometrical optics method that deals with coupled equations for electromagnetic field components, and the Stokes vector formalism (SVF), dealing with Stokes vector components, which are quadratic in electromagnetic field intensity. The equation for the Stokes vector evolution is shown to be derived directly from QIA, whereas the inverse cannot be true. Derivation of SVF from QIA establishes a deep unity of these two approaches, which happen to be equivalent up to total phase. It is pointed out that in contrast to QIA, the Stokes vector cannot be applied for a polarization analysis of the superposition of coherent electromagnetic beams. Additionally, the ability of QIA to describe a normal modes conversion in inhomogeneous media is emphasized.

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Polarization-Angle-Scanning 2DIR Spectroscopy of Coupled Anharmonic Oscillators: A Polarization Null Angle Method

The Journal of Physical Chemistry B ◽

10.1021/jp1102274 ◽

2011 ◽

Vol 115 (18) ◽

pp. 5456-5464 ◽

Cited By ~ 12

Author(s):

Kyung-Koo Lee ◽

Kwang-Hee Park ◽

Sungnam Park ◽

Seung-Joon Jeon ◽

Minhaeng Cho

Keyword(s):

Polarization Angle ◽

Anharmonic Oscillators ◽

Angle Method ◽

2Dir Spectroscopy

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Electromagnetic wave polarization state evolution in weakly anisotropic and nonuniform media with dissipation

Photonics Letters of Poland ◽

10.4302/plp.v9i3.761 ◽

2017 ◽

Vol 9 (3) ◽

pp. 94

Author(s):

Bohdan Bieg ◽

Janusz Chrzanowski

Keyword(s):

Polarization State ◽

Geometrical Optics ◽

Inhomogeneous Media ◽

Plasma Phys ◽

Magnetized Plasma ◽

Tokamak Plasma ◽

Dielectric Tensor ◽

Stokes Vector ◽

Poloidal Magnetic Field ◽

Isotropic Approximation

The change of the polarization state of electromagnetic beam propagating in weakly anisotropic and smoothly inhomogeneous media with dissipation is analysed. On the basis of a quasi-isotropic approximation, which provides the consequent asymptotic solution of Maxwell's equation, the differential equation for the evolution of four component Stokes vector is derived. Obtained equation generalizes previous results for the nonadsorbing media and is written in terms of the dielectric tensor of birefringent media with dissipation. The formalism is illustrated by an example of magnetised plasma with dissipation due to the electron collisions. Full Text: PDF ReferencesK.G.Budden, Radio Waves in the Ionosphere (Cambridge U. Press 1961).V.I.Ginzburg, Propagation of Electromagnetic Waves in Plasma (Gordon & Breach 1970).Yu.A.Kravtsov, ""Quasiisotropic" Approximation to Geometrical Optics", Sov. Phys. Dokl. 13, 1125 (1969).A.A. Fuki, Yu.A. Kravtsov, and O.N. Naida, Geometrical Optics of Weakly Anisotropic Media (Gordon & Breach, Lond., N.Y. 1997).Yu.A. Kravtsov and Yu.I. Orlov, Geometrical optics of inhomogeneous media (Springer Verlag, Berlin, Heidelberg 1990). CrossRef Yu.A. Kravtsov et al., "Waves in weakly anisotropic 3D inhomogeneous media: quasi-isotropic approximation of geometrical optics", Physics-Uspekhi 39, 129(1996). CrossRef F.De Marco, S.E.Segre, "The polarization of an e.m. wave propagating in a plasma with magnetic shear. The measurement of poloidal magnetic field in a Tokamak", Plasma Phys. 14, 245 (1972). DirectLink S.E.Segre, "A review of plasma polarimetry - theory and methods", Plasma Phys. Control. Fusion 41, R57 (1999). CrossRef M. Born and E. Wolf, Principles of Optics (Pergamon, Oxford 1980). CrossRef B.Bieg et al., "Quasi-Isotropic Approximation of Geometrical Optics Method as Adequate Electrodynamical Basis for Tokamak Plasma Polarimetry", Physics Procedia 62, 102 (2015). CrossRef B.Bieg et al., "Two approaches to plasma polarimetry: Angular variables technique and Stokes vector formalism", Nucl. Instr. Meth. Phys. Res. Sect. A 720, 157 (2013). CrossRef S.E.Segre, "New formalism for the analysis of polarization evolution for radiation in a weakly nonuniform, fully anisotropic medium: a magnetized plasma", J. Opt. Soc. Am. A 18, 2601 (2001). CrossRef

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180° rotations in the polarization angle for blazars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936907 ◽

2020 ◽

Vol 636 ◽

pp. A79

Author(s):

M. H. Cohen ◽

T. Savolainen

Keyword(s):

Physical Model ◽

Monitoring Program ◽

Position Angle ◽

Electric Vector ◽

Emission Region ◽

Polarization Angle ◽

Stokes Vector ◽

Winding Number ◽

Phase Effect ◽

Polarized Emission

Rotations of the electric vector position angle (EVPA) in blazars are often close to an integral multiple of 180°. There are many examples of this in the literature, and we strengthen the evidence by showing that, in the RoboPol monitoring program, nπ rotations occur more frequently than otherwise expected by chance. We explain this using a model consisting of two polarized emission components: a “jet” that is constant in time and a “burst” that is variable. The EVPA of the combination is EVPAjet at both the beginning and the end of the burst, so the net rotation across the burst must be nπ. Several examples of this model are analyzed on the Stokes plane, where the winding number for the Stokes vector of the combination gives the value of n. The main conclusion is that the EVPA rotation can be much larger than the physical rotation of the emission region around the axis of the jet, but this requires the EVPAs of the jet and the burst to be nearly orthogonal. Shock-in-jet calculations can provide a physical model for our toy model and in addition they automatically give the required orthogonality. The model is illustrated with data from the literature on OJ 287. We suggest that the large rapid EVPA rotation seen in OJ 287 might be a phase effect and not representative of a physical rotation.

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