Laboratory measurements of oblique whistler-mode wave polarization

The polarization of oblique and parallel whistler-mode waves is a key parameter in determining the nature of wave-particle interactions with electrons. Satellite data have produced surprising evidence that oblique whistler-mode waves in the magnetosphere are circularly polarized, a finding that is consequential for accurately modeling Earth’s radiation belts (Tsurutani, JGR 2009). To explore the nature of whistler-mode wave-particle interactions in the lab, an antenna array has been constructed to launch whistler-mode waves in the PHAse Space MApping (PHASMA) facility at West Virginia University. Data from a movable magnetic pickup coil give wave field components, their relative amplitudes, and their phase, all as a function of wave normal angle. This has enabled the first detailed comparison of oblique whistler-mode wave polarization with three-dimensional cold plasma theory, a necessary precursor to studying the wave-particle interactions responsible for space weather phenomena in the radiation belts.