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Characterizing auroral absorption based on geomagnetic hourly range
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  • Robyn A. D. Fiori,
  • Larisa Trichtchenko,
  • Emma Spanswick,
  • Christopher Balch,
  • Samuel Groleau
Robyn A. D. Fiori
Natural Resources Canada

Corresponding Author:[email protected]

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Larisa Trichtchenko
Natural Resources Canada
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Emma Spanswick
University of Calgary
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Christopher Balch
NOAA SWPC
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Samuel Groleau
Natural Resources Canada
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Abstract

Energetic electron precipitation is a source of both ionospheric and geomagnetic disturbances. The resultant increased ionization in the auroral oval leads to the absorption of high frequency radio waves in the auroral zone, or auroral absorption. Auroral absorption is typically characterized by global geomagnetic activity indices, such as the Kp index. In this paper the hourly range of the magnetic field (HR) is examined as an alternative to the 3-hour Kp index for describing the dynamic and localized features of auroral absorption represented by the hourly range of absorption (HRA). Kp, magnetometer, and riometer data were examined for a 3-year period for stations spread across typical auroral latitudes. A general linear relationship was shown to exist between Kp and LOG(HRA) for Kp<4; for Kp≥4 the correlation was weaker. A stronger linear correlation was demonstrated between LOG(HRA) and LOG(HR) for HR >50 nT, characterized by a correlation coefficient of R=0.63. Increased variability in the relationship between HRA and Kp was attributed to the following factors: the variability of the magnetic field within the 3-hour window characterized by the Kp-index which was better represented by a 1-hour HR; the dependence of the Kp index on sub-auroral magnetic data which is not subject to the energetic electron precipitation experienced within the auroral region; and reduced statistics for Kp>6.