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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 5
Ann. Geophys., 22, 1705–1718, 2004
https://doi.org/10.5194/angeo-22-1705-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 1705–1718, 2004
https://doi.org/10.5194/angeo-22-1705-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  08 Apr 2004

08 Apr 2004

High-latitude propagation studies using a meridional chain of LF/MF/HF receivers

J. LaBelle J. LaBelle
  • Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire, USA

Abstract. For over a decade, Dartmouth College has operated programmable radio receivers at multiple high-latitude sites covering the frequency range 100-5000kHz with about a 1-s resolution. Besides detecting radio emissions of auroral origin, these receivers record characteristics of the ionospheric propagation of natural and man-made signals, documenting well-known effects, such as the diurnal variation in the propagation characteristics of short and long waves, and also revealing more subtle effects. For example, at auroral zone sites in equinoctial conditions, the amplitudes of distant transmissions on MF/HF frequencies are often enhanced by a few dB just before they fade away at dawn. The polarization and/or direction of the arrival of ionospherically propagating signals in the lower HF range (3-5MHz) show a consistent variation between pre-midnight, post-midnight, and pre-dawn conditions. As is well known, magnetic storms and substorms dramatically affect ionospheric propagation; data from multiple stations spanning the invariant latitude range 67-79° reveal spatial patterns of propagation characteristics associated with magnetic storms and substorms. For example, in the hours preceding many isolated substorms, favorable propagation conditions occur at progressively lower latitudes as a function of time preceding the substorm onset. For some of these effects, explanations follow readily from elementary ionospheric physics, but understanding others requires further investigation.

Key words. Magnetospheric physics (annual phenomena) – Radio science (ionosphere propagation; radio-wave propagation)6

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