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.