Statistical observations of the MLT, latitude and size of pulsed ionospheric ̄ows with the CUTLASS Finland radar

A study has been performed on the occurrence of pulsed ionospheric ̄ows as detected by the CUTLASS Finland HF radar. These ̄ows have been suggested as being created at the ionospheric footprint of newly-reconnected ®eld lines, during episodes of magnetic ̄ux transfer into the terrestrial magnetosphere ( ̄ux transfer events or FTEs). Two years of both hightime resolution and normal scan data from the CUTLASS Finland radar have been analysed in order to perform a statistical study of the extent and location of the pulsed ionospheric ̄ows. We note a great similarity between the statistical pattern of the coherent radar observations of pulsed ionospheric ̄ows and the traditional low-altitude satellite identi®cation of the particle signature associated with the cusp/cleft region. However, the coherent scatter radar observations suggest that the merging gap is far wider than that proposed by the Newell and Meng model. The new model for cusp low-altitude particle signatures, proposed by Lockwood and Onsager and Lockwood provides a uni®ed framework to explain the dayside precipitation regimes observed both by the low-altitude satellites and by coherent scatter radar detection.