Whistlers are magnetized plasma waves in planetary magnetospheres. Bounded whistlers, known as helicons, can create high-density laboratory plasmas. We demonstrate reversal of the plasma discharge direction by changing either antenna helicity or magnetic field direction. Simulations reproduce these findings only in the presence of a radial density gradient. Inclusion of such a gradient in the wave equation gives rise to azimuthal shear currents, which for the first time consistently explains the preference of right- over left-handed whistlers and the discharge directionality in helicon plasmas.
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Discharge Directionality and Dominance of Right-Handed Modes in Helicon Plasmas due to Radial Electron Density Gradients
Helicon waves are magnetized plasma waves, similar to whistler waves in Earth's ionosphere, that are used to create high-density laboratory plasmas. We demonstrate that the discharge direction can be reversed by changing the antenna helicity or the magnetic field direction. Simulations reproduce these findings if a radial density gradient exists. A helicon wave equation that includes such a density gradient gives rise to a modulating magnetic field that amplifies right-handed but attenuates left-handed helicon modes. This explains for the first time consistently the dominance of right-handed over left-handed modes and the discharge directionality in helicon plasmas.
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- Award ID(s):
- 1903316
- PAR ID:
- 10436307
- Date Published:
- Journal Name:
- arXivorg
- Volume:
- https://arxiv.org/abs/2212.11401
- ISSN:
- 2331-8422
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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