scholarly journals On the group velocity of whistling atmospherics

2021 ◽  
Vol 7 (4) ◽  
pp. 67-70
Author(s):  
Anatol Guglielmi ◽  
Boris Klain ◽  
Alexander Potapov
Keyword(s):  
Group Velocity ◽  
Electromagnetic Waves ◽  
Theoretical Study ◽  
Lightning Discharge ◽  
Dynamic Spectrum ◽  
Invariance Condition ◽  
Group Delay Time ◽  
Near Earth Space ◽  
Broadband Pulse ◽  
Wave Phenomena

The dynamic spectrum of a whistling atmospheric is a signal of falling tone, and the group delay time of the signal as a function of frequency is formed as a result of propagation of a broadband pulse in a medium (magnetospheric plasma) with a quadratic dispersion law. In this paper, we show that for quadratic dispersion the group velocity is invariant under Galilean transformations. This means that, contrary to expectations, the group velocity is paradoxically independent of the velocity of the medium relative to the observer. A general invariance condition is found in the form of a differential equation. To explain the paradox, we introduce the concept of the dynamic spectrum of Green’s function of the path of propagation of electromagnetic waves from a pulse source (lightning discharge in the case of a whistling atmospheric) in a dispersive medium. We emphasize the importance of taking into account the motion of plasma in the experimental and theoretical study of electromagnetic wave phenomena in near-Earth space.

scholarly journals On the group velocity of whistling atmospherics

2021 ◽  
Vol 7 (4) ◽  
pp. 70-74
Author(s):  
Anatol Guglielmi ◽  
Boris Klain ◽  
Alexander Potapov
Keyword(s):  
Group Velocity ◽  
Electromagnetic Waves ◽  
Theoretical Study ◽  
Lightning Discharge ◽  
Dynamic Spectrum ◽  
Invariance Condition ◽  
Group Delay Time ◽  
Near Earth Space ◽  
Broadband Pulse ◽  
Wave Phenomena

The dynamic spectrum of a whistling atmospheric is a signal of falling tone, and the group delay time of the signal as a function of frequency is formed as a result of propagation of a broadband pulse in a medium (magnetospheric plasma) with a quadratic dispersion law. In this paper, we show that for quadratic dispersion the group velocity is invariant under Galilean transformations. This means that, contrary to expectations, the group velocity is paradoxically independent of the velocity of the medium relative to the observer. A general invariance condition is found in the form of a differential equation. To explain the paradox, we introduce the concept of the dynamic spectrum of Green’s function of the path of propagation of electromagnetic waves from a pulse source (lightning discharge in the case of a whistling atmospheric) in a dispersive medium. We emphasize the importance of taking into account the motion of plasma in the experimental and theoretical study of electromagnetic wave phenomena in near-Earth space.

On electromagnetic waves with a negative group velocity

2010 ◽  
Vol 36 (13) ◽  
pp. 1129-1139
Author(s):  
V. P. Makarov ◽  
A. A. Rukhadze ◽  
A. A. Samokhin
Keyword(s):  
Group Velocity ◽  
Electromagnetic Waves ◽  
Negative Group ◽  
Negative Group Velocity

scholarly journals Быстрые и медленные электромагнитные волны в продольно намагниченном тонкопленочном ферромагнитном метаматериале

2019 ◽  
Vol 45 (23) ◽  
pp. 14
Author(s):  
М.Д. Амельченко ◽  
С.В. Гришин ◽  
Ю.П. Шараевский
Keyword(s):  
Thin Film ◽  
Electromagnetic Waves ◽  
Theoretical Study ◽  
Ferromagnetic Film ◽  
Thin Metal ◽  
Periodic Lattice ◽  
Frequency Range ◽  
Cutoff Frequencies ◽  
Left Handed ◽  
Metal Wires

The results of a theoretical study of the electrodynamic characteristics of fast and slow electromagnetic waves (EMWs) propagating in a metamaterial are presented. The metamaterial consists of a ferromagnetic film inside which a periodic lattice of thin metal wires is located. It has been established that the ferromagnetic thin-film metamaterial possesses the properties of a left-handed medium at frequencies of slow electromagnetic waves. It is shown that, in a ferromagnetic metamaterial, compared with a conventional ferromagnetic film, the cutoff frequencies of fast and slow EMWs shift to a higher frequency range, and EMWs themselves become strongly slowed waves.

scholarly journals Дважды отрицательные среды на основе антиферромагнитных полупроводников для терагерцевого диапазона частот

2022 ◽  
Vol 48 (5) ◽  
pp. 39
Author(s):  
С.В. Гришин ◽  
А.В. Богомолова ◽  
С.А. Никитов
Keyword(s):  
Electromagnetic Waves ◽  
Theoretical Study ◽  
The Other ◽  
Terahertz Range ◽  
Dispersion Characteristics ◽  
Gyrotropic Medium ◽  
Material Parameters

The paper presents the results of a theoretical study of the dispersion characteristics of electromagnetic waves (EMW) existing in a transversely magnetized antiferromagnetic (AFM) semiconductor with loss. An AFM semiconductor is an infinite bi-gyrotropic medium, the effective material parameters of which are twice negative in several frequency ranges. It was found that these frequency regions are in the terahertz range and there are four backward EMEs in them, two of which are TE waves, and the other two are TM waves.

Search for Martian Schumann Resonances

2020 ◽  
Author(s):  
Yanan Yu ◽  
Christopher Russell ◽  
Peter Chi ◽  
Syed Haider ◽  
Jayesh Pabari ◽  
...  
Keyword(s):  
Fundamental Mode ◽  
Electromagnetic Waves ◽  
Lightning Discharge ◽  
Sampling Rate ◽  
Dust Storms ◽  
Dust Particles ◽  
Fluxgate Magnetometer ◽  
Electric Discharges ◽  
Schumann Resonance ◽  
Schumann Resonances

<p>On Earth, electric discharges in thunderstorms produce ELF waves in the Earth-ionosphere waveguide that circles the globe. These waves give rise to Schumann resonances in the waveguide resonant cavity. These waves are also expected to occur at Venus, produced by strong lightning in the Venus atmosphere and at Mars produced by active dust devils or dust storms, during southern hemisphere summer, when the planet is near periapsis. Within dust storms, dust particles undergo triboelectric charging. The charge transfer leads to charge separation. A lightning discharge is expected to occur when the charge exceeds the breakdown strength of the media present. The transient electric discharge emits electromagnetic waves in the VLF/ELF range of frequency, leading to Schumann Resonance in the surface-ionospheric cavity. In a heterogeneous cavity, Schumann resonance modes are observable using an in-situ instrument. Recently has it been possible to search for these electromagnetic waves from the Mars surface using the UCLA-provided InSight fluxgate magnetometer. The weakness of the vertical component of ULF waves at Mars suggests that the subsurface is electrically conducting, allowing trapping of electromagnetic energy between the sub-surface and the ionosphere. The fundamental mode of Schumann resonance carries higher energy compared to there are more chances of observing the fundamental mode. Various values of the first mode are predicted in the literature for Mars like 13-14 Hz or between 9-14 Hz and 17.5 Hz. Even if the fundamental mode is above 10 Hz, the 20 Hz sampling rate will allow detection of an aliased signal. We examine the data obtained during Martian sandstorms for the possible existence of such waves. A large dust storm was detected on Mars beginning on InSight sols 40 to 50, and ending during sols 50 to 90. Examining the 20 Hz InSight magnetometer data during this period reveals no clearly identifiable Schumann Resonance signals within the bandwidth of the magnetometer.</p>

Absorbing boundary conditions for low group velocity electromagnetic waves in photonic crystals

2011 ◽  
Vol 50 (9) ◽  
pp. 1266 ◽  
Author(s):  
Murtaza Askari ◽  
Babak Momeni ◽  
Charles M. Reinke ◽  
Ali Adibi
Keyword(s):  
Photonic Crystals ◽  
Boundary Conditions ◽  
Group Velocity ◽  
Electromagnetic Waves ◽  
Absorbing Boundary Conditions ◽  
Absorbing Boundary

Theoretical study of optically-controlled group velocity of light in an optical fiber

2010 ◽  
Author(s):  
Xianpu Su ◽  
Xiaoyan Li ◽  
Shoujun Zhang ◽  
Xiaodan Wei ◽  
Ming Feng ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Group Velocity ◽  
Theoretical Study ◽  
Velocity Of Light

scholarly journals Computational and theoretical study of the wave-particle interaction of protons and waves

2012 ◽  
Vol 30 (9) ◽  
pp. 1361-1369 ◽  
Author(s):  
P. S. Moya ◽  
A. F. Viñas ◽  
V. Muñoz ◽  
J. A. Valdivia
Keyword(s):  
Numerical Simulation ◽  
Solar Wind ◽  
Electromagnetic Waves ◽  
Theoretical Study ◽  
Nonlinear Evolution ◽  
Particle Interaction ◽  
Wave Particle Interaction ◽  
One Dimensional ◽  
Proton Temperature ◽  
Spherical Expansion

Abstract. We study the wave-particle interaction and the evolution of electromagnetic waves propagating through a plasma composed of electrons and protons, using two approaches. First, a quasilinear kinetic theory has been developed to study the energy transfer between waves and particles, with the subsequent acceleration and heating of protons. Second, a one-dimensional hybrid numerical simulation has been performed, with and without including an expanding-box model that emulates the spherical expansion of the solar wind, to investigate the fully nonlinear evolution of this wave-particle interaction. Numerical results of both approaches show that there is an anisotropic evolution of proton temperature.

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