Excitation Of Upper Hybrid Waves Research Articles

Excitation of upper hybrid wave by cross focused q-Gaussian laser beams in graded index plasma channel

Excitation of upper hybrid wave by cross focused q-Gaussian laser beams in graded index plasma channel

Beam driven upper-hybrid-wave instability in quantized semiconductor plasmas

The excitation of Upper-Hybrid waves (UHWs) induced by electron beam in semiconductor plasma is examined using quantum hydrodynamic model. Various quantum effects are taken into account including recoil effect, Fermi degenerate pressure, and exchange-correlation potential. The bandwidth of the UHWs spectrum shows that the system supports purely growing unstable mode. The latter has been studied for diversified parameters of nano-sized GaAs semiconductor.

Excitation of upper-hybrid waves by a gyrating relativistic electron beam in a magnetized dusty plasma cylinder

A gyrating relativistic electron beam propagating through a magnetized dusty plasma cylinder drives an upper-hybrid wave to instability via cyclotron interaction. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the typical parameters of dusty plasma experiments. It is found that as the density ratio of negatively charged dust grains to electrons increases, the unstable mode frequency of the upper-hybrid waves increases. Moreover, the growth rate of the instability also increases with the density ratio. The growth rate of the unstable mode has the largest value for the modes whose eigenfunctions peak at the location of the beam. The growth rate of the unstable mode scales as the one-third power of the beam density.

Computer simulations for direct conversion of the HF electromagnetic wave into the upper hybrid wave in ionospheric heating experiments

Abstract. Excitation of upper hybrid waves associated with the ionospheric heating experiments is assumed to be essential in explaining some of the features of stimulated electromagnetic emissions (SEE). A direct conversion process is proposed as an excitation mechanism of the upper hybrid waves where the energy of an obliquely propagating electromagnetic pump wave is converted into the electrostatic upper hybrid waves due to small-scale density irregularities. We performed electromagnetic particle-in-cell simulations to investigate the energy conversion process in the ionospheric heating experiments. We studied dependence of the amplitude of the excited wave on the propagation angle of the pump wave, scale length of the density irregularity, degree of the irregularity, and thermal velocity of the plasma. The maximum amplitude is found to be 37 of the pump amplitude under an optimum condition.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; wave-particle interactions).

Excitation of upper-hybrid waves by a rotating relativistic electron beam in a plasma-filled large-orbit gyrotron

A large-orbit gyrotron may operate at higher beam currents if one introduces a plasma in its interaction region. The plasma, however, is unstable to an upper-hybrid electrostatic perturbation driven via cyclotron interaction by the rotating relativistic electron beam. The growth rate of the instability is comparable to the growth rate of the cyclotron maser instability when the plasma frequency is of the order of the electron cyclotron frequency.

Generation models of electron conies

Electron distribution functions with a peak oblique to the magnetic field, adjacent to but distinct from loss cone features, have been observed by the DE 1, Viking and S3‐3 spacecraft in passes through the nightside auroral zone, polar cap, dayside cusp and extended dayside auroral oval. Using particle simulations, we investigate two types of wave excitation and particle acceleration mechanisms which may contribute to producing these electron conic distributions. The first involves excitation of upper hybrid waves by the electron loss cone, and the subsequent perpendicular heating of the background and thermal electrons. The second involves excitation of downward propagating parallel modes by an auroral electron beam which frequently accompanies the upflowing electron conics. These modes provide parallel acceleration, which modifies the electron distribution function. Those electrons which are not lost to the atmosphere and mirror back up the magnetic field line give rise to enhancements in the distribution function at the edge of the loss cone.