SIMULTANEOUS OBSERVATIONS AT DIFFERENT ALTITUDES OF IONOSPHERIC BACKSCATTER IN THE EASTWARD ELECTROJET

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.