Whistler Wave Emission from a Modulated Electron Beam in a Collisional Magnetoplasma in the Presence of a Density Duct

Abstract

UDC 533.951We study the radiation from a modulated electron beam injected along the axis of a cylindrical density duct in a magnetoplasma. An expression for the average power lost by the beam at the modulation frequency is obtained and analyzed. It is shown that in the case ofČerenkov resonance of the beam with a weakly damped whistler mode of an enhanced-density duct, a noticeable increase in this power is possible compared with the case where the beam is injected in a homogeneous background magnetoplasma. Based on the results of numerical calculations performed for conditions of the Earth's ionosphere, we give estimates of an increase in the power radiated from the beam in the whistler frequency range in the presence of a cylindrical duct with enhanced density.

Whistler wave emission by a modulated electron beam injected into a plasma column surrounded by a uniform medium

“…Moreover, an axially magnetized plasma column surrounded by a dielectric or by free space is able to guide waves propagating in this frequency range. As already shown for the case of modulated beam emission into artificially created density ducts [17,18], the authors expect that a noticeable increase of whistler radiation power should be observed at Cherenkov resonance conditions when the beam is injected into a plasma column surrounded by a dielectric medium, compared to the case when it is injected into a homogeneous unbounded background magnetoplasma. In this paper we aim to demonstrate this fact and to determine the beam radiation power as a function of the medium dielectric permittivity, the main characteristics of the plasma column (radius, plasma density and electron collision frequency) and of the beam (radius and energy).…”

“…During the past four decades, a large number of papers have been published regarding the linear and nonlinear theory of whistler wave excitation by pulsed and density modulated electron beams injected in unbounded homogeneous magnetized plasmas (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and references therein). Recently [17][18][19][20], the authors studied the efficiency of whistler radiation by such beams injected along the background magnetic field into density ducts artificially created in laboratory or space plasmas [21][22][23][24][25][26][27][28]. In particular, they showed that the time-averaged power lost by the beam in the presence of a duct of enhanced plasma density can increase noticeably owing to resonant Cherenkov excitation of guided whistler modes at the beam modulation frequency [17,18].…”

“…Recently [17][18][19][20], the authors studied the efficiency of whistler radiation by such beams injected along the background magnetic field into density ducts artificially created in laboratory or space plasmas [21][22][23][24][25][26][27][28]. In particular, they showed that the time-averaged power lost by the beam in the presence of a duct of enhanced plasma density can increase noticeably owing to resonant Cherenkov excitation of guided whistler modes at the beam modulation frequency [17,18]. This paper studies the coherent spontaneous whistler emission by a modulated thin electron beam injected into a magnetic-field-aligned cylindrical plasma column surrounded by any uniform isotropic medium (dielectric, free space, metal, etc.).…”

Electromagnetic wave radiation by an electron beam spiraling in a magnetized plasma column

“…[13][14][15][16][17][18][19][20][21] The authors have already developed a general theory about the resonant linear excitation of waves by modulated electron beams injected parallel to the ambient magnetic field into artificially created cylindrical density ducts in laboratory and space plasmas. [31][32][33] In particular, they have shown that the power radiated by such beams in the presence of enhanced-density ducts increases noticeably due to the Cherenkov excitation of guided whistler modes. In the present work, the theoretical model developed previously 31,32 is extended to the case of spiraling beams radiating in magnetized plasma columns surrounded by homogeneous media as dielectric, free space, or plasma.…”

“…[31][32][33] In particular, they have shown that the power radiated by such beams in the presence of enhanced-density ducts increases noticeably due to the Cherenkov excitation of guided whistler modes. In the present work, the theoretical model developed previously 31,32 is extended to the case of spiraling beams radiating in magnetized plasma columns surrounded by homogeneous media as dielectric, free space, or plasma. Such situations can be realized for example in typical laboratory experiments involving whistler excitation by beams or antennas, where the discharge plasma column is often separated from the walls of the setup chamber by a layer of rarefied plasma.…”