Se. Milan et M. Lester, SIMULTANEOUS OBSERVATIONS AT DIFFERENT ALTITUDES OF IONOSPHERIC BACKSCATTER IN THE EASTWARD ELECTROJET, Annales geophysicae, 16(1), 1998, pp. 55-68
A common feature of evening near-range ionospheric backscatter in the
CUTLASS Iceland radar field of view is two parallel, approximately L-s
hell-aligned regions of westward flow which are attributed to irregula
rities in the auroral eastward electrojet region of the ionosphere. Th
ese backscatter channels are separated by approximately 100-200 km in
range. The orientation of the CUTLASS Iceland radar beams and the zona
lly aligned nature of the flow allows an approximate determination of
flow angle to be made without the necessity of bistatic measurements.
The two flow channels have different azimuthal variations in flow velo
city and spectral width. The nearer of the two regions has two distinc
t spectral signatures. The eastern beams detect spectra with velocitie
s which saturate at or near the ion-acoustic speed, and have low spect
ral widths (less than 100 m s(-1)), while the western beams detect low
er velocities and higher spectral widths (above 200 m s(-1)). The more
distant of the two channels has only one spectral signature with velo
cities above the ion-acoustic speed and high spectral widths. The spec
tral characteristics of the backscatter are consistent with E-region s
catter in the nearer channel and upper-E-region or F-region scatter in
the further channel. Temporal variations in the characteristics of bo
th channels support current theories of E-region turbulent heating and
previous observations of velocity-dependent backscatter cross-section
. In future, observations of this nature will provide a powerful tool
for the investigation of simultaneous E- and F-region irregularity gen
eration under similar (nearly co-located or magnetically conjugate) el
ectric field conditions.