A phased array for laboratory testing of radiation belt whistler-mode wave dynamics*

Whistler-mode waves are found in the Earth's outer radiation belt, where the electron population is highly variable. It is believed that whistler-mode waves play a role in accelerating electrons in this belt. Wave normal angle is predicted to be an important factor in these interactions. Because of diagnostic advances, there are new opportunities to study the effect of wave normal angle on wave-particle interactions in the laboratory with high precision. A phased array antenna has been constructed to launch whistler-mode waves in the PHAse Space MApping (PHASMA) facility at West Virginia University. A cold plasma model of the antenna array has been developed to guide experimental design. 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, enabling one of the most detailed comparisons of data with cold plasma theory. This robust understanding of the waves being generated is a necessary precursor to studying the wave-particle interactions responsible for space weather phenomena in the radiation belts.