Generation of whistler waves by a rotating magnetic field source

Abstract

The paper discusses the generation of polarized whistler waves radiated from a rotating magnetic field source created via a novel phased orthogonal two loop antenna. The results of linear three-dimensional electron magnetohydrodynamics simulations along with experiments on the generation whistler waves by the rotating magnetic field source performed in the large plasma device are presented. Comparison of the experimental results with the simulations and linear wave properties shows good agreement. The whistler wave dispersion relation with nonzero transverse wave number and the wave structure generated by the rotating magnetic field source are also discussed. The phase velocity of the whistler waves was found to be in good agreement with the theoretical dispersion relation. The exponential decay rate of the whistler wave propagating along the ambient magnetic field is determined by Coulomb collisions. In collisionless case the rotating magnetic field source was found to be a very efficient radiation source for transferring energy along the ambient magnetic field lines.

Waves guided by density ducts in magnetoplasma in the nonresonant region of the whistler frequency range

“…The propagation constant of this mode is . It can easily be verified that the value of the propagation constant lies in interval (19). In this case, the quantities determining the field outside the duct, are real and the mode turns out to be localized (eigenmode).…”

“…When the frequency increases and approaches the lower hybrid resonance frequency, the accuracy of the approximate solution considerably degrades. With decreasing frequency, the mode propagation constant approaches the lower boundary of region (19). After crossing this boundary, the mode ceases to be localized and becomes leaky.…”

“…This condition is satisfied for for all real values of and for at , where . It should be noted that analysis of dispersion relation (13) showed that, in the frequency range under consideration, eigenmodes exist only in a duct with enhanced density and their propagation constants lie within the interval (19) where…”

“…As is known [17,18], such guiding structures can appear in magnetoplasma as a result of nonlinear interaction of the fields of electromagnetic sources with the ambient (background) plasma medium. It should be noted that interest in specific features of the behavior of whistler waves in region (1) was stimulated in the past decade by a number of new experimental studies aimed at developing efficient methods of wave excitation in the indicated frequency range (see, e.g., [19]). …”

Efficient spectral and pseudospectral algorithms for 3D simulations of whistler-mode waves in a plasma

“…Fig. 2 shows a comparison between the computed and experimentally measured rotating magnetic fields [4,5] generated by a two loop antenna, where the experiments were conducted in the conditions for which linear approximation should be acceptable. Here the imaging plane is taken to be a z-slice (xy-plane at some z).…”