Virtual height characteristics of ionospheric and ground scatter
observed by mid-latitude SuperDARN HF radars
Abstract
Propagation of high-frequency (HF) radio signals is strongly dependent
on the ionospheric electron density structure along a communications
link. The ground-based, HF space weather radars of the Super Dual
Auroral Radar Network (SuperDARN) utilize the ionospheric refraction of
transmitted signals to monitor the global circulation of E- and F-region
plasma irregularities. Previous studies have assessed the propagation
characteristics of backscatter echoes from ionospheric irregularities in
the auroral and polar regions of the Earth’s ionosphere. By default, the
geographic location of these echoes are found using empirical models
which estimate the virtual backscattering height from the measured range
along the radar signal path. However, the performance of these virtual
height models has not yet been evaluated for mid-latitude SuperDARN
radar observations or for ground scatter propagation modes. In this
study, we derive a virtual height model suitable for mid-latitude
SuperDARN observations using 5 years of data from the Christmas Valley
East and West radars. This empirical model can be applied to both
ionospheric and ground scatter observations and provides an improved
estimate of the ground range to the backscatter location compared to
existing high-latitude virtual height models. We also identify a region
of overlapping half-hop F-region ionospheric scatter and one-hop
E-region ground scatter where the measured radar parameters (e.g.,
velocity, spectral width, elevation angle) are insufficient to
discriminate between the two scatter types. Further studies are required
to determine whether these backscatter echoes of ambiguous origin are
observed by other mid-latitude SuperDARN radars and their potential
impact on scatter classification schemes.