Transition of Pi2 ULF wave polarization structure from the ionosphere to the ground

Authors

  • P. V. Ponomarenko,

    Corresponding author
    1. Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
    2. School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, New South Wales, Australia
    • Corresponding author: P. V. Ponomarenko, Institute of Space and Atmospheric Studies, 116 Science Place, Saskatoon, SK, S7N 5E2, Canada. (pasha.ponomarenko@usask.ca)

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  • C. L. Waters

    1. School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, New South Wales, Australia
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Abstract

[1] Trains of ultra low frequency (ULF) waves in the Pi2 range (40–150 s) are regularly detected in near-Earth space. While some Pi2 occur just before substorm onset, others do not show any casual relation to substorm activity so that the Pi2 generation and propagation mechanisms are still unclear. The bulk of information on Pi2 morphology is provided by ground-based magnetometers, subject to distortions due to transition through the highly conducting lower ionosphere. While space-borne magnetometers provide important in situ information, they cannot match the spatio-temporal continuity of ground-based instruments. In this paper, we devise a novel approach using co-located high-frequency ionospheric radars and ground magnetometers for the first direct observation of the Pi2 wave polarization transition between the ionosphere and the ground. Furthermore, application of the Hilbert transform enables us to reconstruct the transition dynamics, which resolves an apparent disagreement between the Pi2 spectra measured by the two instruments.

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