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Ann. Geophys., 23, 3457-3471, 2005
www.ann-geophys.net/23/3457/2005/
© European Geosciences Union 2005
A numerical model to investigate the polarisation azimuth of ULF waves through an ionosphere with oblique magnetic fields
M. D. Sciffer, C. L. Waters, and F. W. Menk
School of Mathematical and Physical Sciences and CRC for Satellite Systems, The University of Newcastle, New South Wales, Australia
Abstract. A one dimensional, computational model for the propagation of ultra low
frequency (ULF; 1-100 mHz) wave fields from the Earth's magnetosphere
through the ionosphere, atmosphere and into the ground is presented. The
model is formulated to include solutions for high latitudes where the Earth's
magnetic field, (B0), is near vertical and for oblique magnetic
fields applicable at lower latitudes. The model is used to investigate the
wave polarisation azimuth in the magnetosphere compared with the ground wave
fields, as a function of the dip angle of B0. We find that for
typical ULF wave scale sizes, a 90° rotation of the wave polarisation
azimuth from the magnetosphere to the ground occurs at high latitudes.
However, this effect does not necessarily occur at lower latitudes in all
cases. We show that the degree to which the wave polarisation azimuth rotates
critically depends on the properties of the compressional ULF wave mode.
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