NEW TECHNIQUES FOR AURORAL IRREGULARITY STUDIES WITH COSCAT

The COSCAT system enables the detection of E-region auroral backscatte r with the EISCAT remote receivers at magnetic aspect angles close to 90 degrees. This is achieved by utilising a low-power transmitter stat ioned in Oulu, Finland. Many important observations of E-region irregu larities have been achieved with this simple experiment. Recent studie s have attempted to push the COSCAT system to its experimental limits. Firstly, the CW signal has been phase-modulated with 13-bit Barker co des with baud lengths of 40, 70 and 100 mu s. Interpretation of the re ceived power allows the spatial distribution of the auroral scatterers to be determined. The second advance is in the use of a sophisticated correlator program which allows data to be buffered within the correl ator at very high time resolution. This enables the coherent backscatt er power to be sampled every 12.5 ms and the full auto-correlation fun ction to be measured every 100 ms. These measurements allow the COSCAT system to be employed for the first time in an investigation of the g rowth and decay of the auroral irregularities.