Helicon waves in uniform plasmas. IV. Bessel beams, Gendrin beams, and helicons

Journal Article · Sun May 15 04:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4949348· OSTI ID:22600180

Urrutia, J. M.; Stenzel, R. L. ^[1]

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1. Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

Electromagnetic waves in the low frequency whistler mode regime are investigated experimentally and by digital data superposition. The radiation from a novel circular antenna array is shown to produce highly collimated helicon beams in a uniform unbounded plasma. The differences to Bessel beams in free space are remarked upon. Low divergence beams arise from the parallel group velocity of whistlers with phase velocity either along the guide field or at the Gendrin angle. Waves with angular momentum are produced by phasing the array in the circular direction. The differences in the field topologies for positive and negative modes numbers are shown. It is also shown that in uniform plasmas, the radial amplitude profile of the waves depends on the antenna field topology. Thus, there are no helicon “eigenmodes” with radial Bessel function profiles in uniform plasmas. It is pointed out that phase measurements in helicon devices indicate radial wave propagation which is inconsistent with helicon eigenmode theory based on paraxial wave propagation. Trivelpiece-Gould modes also exist in uniform unbounded plasmas.

• OSTI ID: 22600180
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 23; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
ANGULAR MOMENTUM
ANTENNAS
BEAMS
BESSEL FUNCTIONS
HELICON WAVES
PHASE VELOCITY
PLASMA
TOPOLOGY
WAVE PROPAGATION
WHISTLER INSTABILITY
WHISTLERS