GEOPHYSICAL RESEARCH LETTERS, VOL. 24, NO. 24, PAGES 3161-3164, DECEMBER 15, 1997

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The polarization of auroral radio emissions

S. G. Shepherd, J. LaBelle, and M. L. Trimpi
Department of Physics and Astronomy, Darmouth College, Hanover, New Hampshire
Received September 5, 1997; accepted October 28, 1997

Abstract:

Ground level observations using two vertical loop antennas oriented at 90$^\circ$ to each other reveal the sense of polarization of several types of auroral radio emissions in the frequency range 30-5000 kHz. Auroral hiss is observed to be right elliptically polarized (RP) with respect to the local magnetic field, consistent with theoretical expectation for the whistler mode and with earlier measurements. Two less well-understood auroral emissions, are found to be left elliptically polarized (LP). This polarization is inconsistent with their generation in the X-mode as suggested by some theories.