A reciprocity theorem on the propagation of radio waves via the ionosphere

Budden, K. G.

doi:10.1017/s030500410002973x

Cited by 51 publications

(58 citation statements)

References 3 publications

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“…III, IV, and V, consider Fig. 2, which involves two gyrotropic systems: a chiral system [35][36][37][38][39][40] and a Faraday system [1,8,11,41,42].…”

Section: Electromagnetic Examplementioning

confidence: 99%

Electromagnetic Nonreciprocity

Caloz¹,

Alù²,

Tretyakov³

et al. 2018

Phys. Rev. Applied

485

341

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We aim at providing a global perspective on electromagnetic nonreciprocity and clarifying confusions that arose in recent developments of the field. We provide a general definition of nonreciprocity and classify nonreciprocal systems according to their linear time-invariant (LTI), linear time-variant (LTV), or nonlinear natures. The theory of nonreciprocal systems is established on the foundation formed by the concepts of time reversal, time-reversal symmetry, time-reversal symmetry breaking, and related Onsager-Casimir relations. Special attention is given to LTI systems, the most-common nonreciprocal systems, for which a generalized form of the Lorentz reciprocity theorem is derived. The delicate issue of loss in nonreciprocal systems is demystified and the so-called thermodynamics paradox is resolved from energyconservation considerations. An overview of the fundamental characteristics and applications of LTI, LTV, and nonlinear nonreciprocal systems is given with the help of pedagogical examples. Finally, asymmetric structures with fallacious nonreciprocal appearances are debunked.

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“…III, IV, and V, consider Fig. 2, which involves two gyrotropic systems: a chiral system [35][36][37][38][39][40] and a Faraday system [1,8,11,41,42].…”

Section: Electromagnetic Examplementioning

confidence: 99%

Electromagnetic Nonreciprocity

Caloz¹,

Alù²,

Tretyakov³

et al. 2018

Phys. Rev. Applied

485

341

View full text Add to dashboard Cite

show abstract

“…One could also say that in the adiabatic limit, the photon will remain in the same plus or minus branch, but the character of the mode is changed across the vacuum resonance. Indeed, in the literature on radio wave propagation in plasmas (e.g., Budden 1961;Zheleznyakov et al 1983), the nonadiabatic case, in which the photon state jumps across the continuous curves, is referred to as "linear mode coupling". It is important to note that the "mode conversion" effect discussed here is not a matter of semantics.…”

Section: Wave Propagation In Inhomogeneous Mediummentioning

confidence: 99%

Physics of strongly magnetized neutron stars

Harding¹,

Lai²

2006

Rep. Prog. Phys.

808

763

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Abstract. There has recently been growing evidence for the existence of neutron stars possessing magnetic fields with strengths that exceed the quantum critical field strength of 4.4 × 10 13 G, at which the cyclotron energy equals the electron rest mass. Such evidence has been provided by new discoveries of radio pulsars having very high spin-down rates and by observations of bursting gamma-ray sources termed magnetars. This article will discuss the exotic physics of this high-field regime, where a new array of processes becomes possible and even dominant, and where familiar processes acquire unusual properties. We review the physical processes that are important in neutron star interiors and magnetospheres, including the behavior of free particles, atoms, molecules, plasma and condensed matter in strong magnetic fields, photon propagation in magnetized plasmas, free-particle radiative processes, the physics of neutron star interiors, and field evolution and decay mechanisms. Application of such processes in astrophysical source models, including rotation-powered pulsars, soft gamma-ray repeaters, anomalous X-ray pulsars and accreting X-ray pulsars will also be discussed. Throughout this review, we will highlight the observational signatures of high magnetic field processes, as well as the theoretical issues that remain to be understood.

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“…Because of the anisotropy, the ray deviates from the associated wave normal [e.g., Budden, 1985]. For the isotropic case, the general Snell's law reduces to the classical one.…”

Section: Ray Tracingmentioning

confidence: 99%

Real‐time HF ray tracing through a tilted ionosphere

Huang¹,

Reinisch²

2006

Radio Science

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[1] High-frequency (HF) direction-finding (DF) systems measure the angles of arrival of signals at selected frequencies. With this information, ray tracing can accurately determine the location of the HF transmitters if the three-dimensional (3-D) electron density (Ne) distribution between the DF site and the transmitters is known. The usual approach is to use an ionospheric model like the International Reference Ionosphere (IRI) as a proxy for the density distribution. We describe a more realistic approach developed in cooperation with Codem Systems in Merrimack, New Hampshire. A collocated digisonde at the DF site measures the vertical electron density profile and the local ionospheric tilt, providing, in real time, the inputs for the construction of the 3-D Ne distribution. The vertical profile is automatically obtained from the Automated Real Time Ionogram Scaler with True Height (ARTIST)-scaled ionogram and the local tilt from the sky maps recorded after each ionogram. The characteristics of each layer, for example, critical frequencies and peak heights, are expressed as a function of latitude l and longitude Ψ. In the neighborhood of the DF site each characteristic, for example,The coefficients C 7 and C 8 for any given azimuth direction are determined with the use of the Union Radio Scientifique Internationale/CCIR coefficients (which are also used in IRI), and the calculation of C l and C Ψ makes use of the measured ionospheric tilt data; f o F 2 m is the local, measured f o F 2 value. When the measured density profile and tilt data are available, the derived 3-D density distribution represents the instantaneous ionosphere structure near the site. The numerical ray tracing includes the effects of the magnetic field and properly treats the spitze effect, making the ray-tracing program especially useful for small distances. Ray tracing through simulated tilts shows that the differences in ground distances for one-hop high-frequency (HF) propagation vary from about 1 to 100 km depending on the assumed tilts and distances. Operational tests for distances up to approximately 100 km have demonstrated good results in determining the transmitter location in real time and have illustrated the importance of using the actual ionospheric profiles and tilts in the ray tracing.

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A reciprocity theorem on the propagation of radio waves via the ionosphere

Cited by 51 publications

References 3 publications

Electromagnetic Nonreciprocity

Electromagnetic Nonreciprocity

Physics of strongly magnetized neutron stars

Real‐time HF ray tracing through a tilted ionosphere

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