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Introduction
Published in Igor G. Kondrat’ev, Alexander V. Kudrin, Tatyana M. Zaboronkova, Electrodynamics of Density Ducts in Magnetized Plasmas, 2019
Igor G. Kondrat’ev, Alexander V. Kudrin, Tatyana M. Zaboronkova
In recent decades, a great deal of information has been accumulated on the properties of the very low-frequency (VLF) electromagnetic signals known as whistlers, or whistling atmospherics (see Storey, 1953; Gershman and Ugarov, 1961; Helliwell, 1965; Walker, 1976), which travel in the near-Earth environment roughly in the direction of the geomagnetic field. These signals, at frequencies below the local electron gyrofrequency (which is usually less than the electron plasma frequency in the ionosphere and magnetosphere), propagating over long distances in the earth’s magnetosphere, play an important role in space plasma physics and may serve as a diagnostic tool for investigating the distribution and dynamics of the magnetospheric plasma (Brice and Smith, 1971; Sazhin et al., 1992). It is now believed that whistlers can be guided through the earth’s magnetosphere by ducts, tubes of enhanced or reduced ionization which are aligned with the geomagnetic field (Helliwell, 1965; Walker, 1976). The detailed discussion of characteristics of ducts and their formation mechanisms is beyond the scope of this book. Only a brief outline is given here of the major features of ducts and ducted whistlers.
Time-Varying Medium in a Cavity and the Effect of the Switching Angle
Published in Dikshitulu K. Kalluri, Electromagnetics of Time Varying Complex Media, 2018
Such an R wave is called a whistler wave, since the whistlers in radio reception were explained in terms of the propagation of electromagnetic signals in lightning. The whistler mode is called helicon mode in the literature on solid-state plasmas.
Electromagnetic Waves and Lasers
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
In case of an R wave, the wave is in resonance(k=∞) with the cyclotron motion of the electrons at ω = ωc. The direction of rotation of the plane of polarization and the direction of gyration of the electrons for this wave are the same, causing the wave to lose energy in continuous acceleration of the electrons and making it incapable of propagating. This wave has a cutoff at ω=ωR and a stop-band between ωR and ωc and below ωc, i.e. whenω<ωc and it propagates at a velocity less than the speed of light c. The wave in this low frequency region is called the whistler mode. The whistler waves are extremely useful in the study of ionospheric phenomena. The L wave, on the other hand, has no resonance with the cyclotron motion of the electrons and has a lower cutoff frequency ωL compared with the cutoff frequency ωR of the R wave. This wave could have been in resonance with the motion of ions under the action of magnetic field B→0. Since we have neglected this motion, the term revealing the resonance is not appearing in the dispersion relation of the L wave.
Helicon Injected Inertial Plasma Electrostatic Rocket
Published in Nuclear Technology, 2022
Rohan Puri, George H. Miley, Erik P. Ziehm, Raul Patino, Raad Najam
A helicon wave is a right-handed, circularly polarized electromagnetic (EM) wave (as shown in Fig. 1). It has a lower frequency than a whistler wave and is formed inside a cylindrical tube wrapped by a radio-frequency (RF) antenna.1,2 A magnetic field (MF) setup that provides an axial magnetic flux inside the helicon tube completes the propellant ionization system.