jgra50475.pdf (2.18 MB)
On the spatial distribution of decameter-scale subauroral ionospheric irregularities observed by SuperDARN radars
journal contribution
posted on 2014-04-08, 09:37 authored by S. de Larquier, P. Ponomarenko, A. J. Ribeiro, J. M. Ruohoniemi, J. B. H. Baker, K. T. Sterne, Mark LesterThe midlatitude Super Dual Auroral Radar Network (SuperDARN) radars
regularly observe nighttime low-velocity Sub-Auroral Ionospheric Scatter (SAIS) from
decameter-scale ionospheric density irregularities during quiet geomagnetic conditions.
To establish the origin of the density irregularities responsible for low-velocity SAIS, it is
necessary to distinguish between the effects of high frequency (HF) propagation and
irregularity occurrence itself on the observed backscatter distribution. We compare range,
azimuth, and elevation data from the Blackstone SuperDARN radar with modeling results
from ray tracing coupled with the International Reference Ionosphere assuming a uniform
irregularity distribution. The observed and modeled distributions are shown to be very
similar. The spatial distribution of backscattering is consistent with the requirement that
HF rays propagate nearly perpendicular to the geomagnetic field lines (aspect angle ≤ 1°).
For the first time, the irregularities responsible for low-velocity SAIS are determined to
extend between 200 and 300 km altitude, validating previous assumptions that
low-velocity SAIS is an F-region phenomenon. We find that the limited spatial extent of
this category of ionospheric backscatter within SuperDARN radars’ fields-of-view is a
consequence of HF propagation effects and the finite vertical extent of the scattering
irregularities. We conclude that the density irregularities responsible for low-velocity
SAIS are widely distributed horizontally within the midlatitude ionosphere but are
confined to the bottom-side F-region.
History
Citation
Journal of Geophysical Research: Space Physics, 2013, 118 (8), pp. 5244-5254Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and AstronomyVersion
- VoR (Version of Record)