Coherent EISCAT Svalbard Radar spectra from the dayside cusp/cleft and their implications for transient field-aligned currents

Naturally enhanced incoherent scatter spectra from the vicinity of the days ide cusp/cleft, interpreted as being due to plasma turbulence driven by sho rt bursts of intense field-aligned current, are compared with high-resoluti on narrow-angle auroral images and meridian scanning photometer data. Enhan ced spectra have been observed on many occasions in association with nights ide aurora, but there has been only one report of such spectra seen in the cusp/cleft region. Narrow-angle images show considerable change in the auro ra on timescales shorter than the 10-s radar integration period, which coul d explain spectra observed with both ion lines simultaneously enhanced. Enh anced radar spectra are generally seen inside or beside regions of 630-nm a uroral emission, indicative of sharp F region conductivity gradients, but t here appears also to be a correlation with dynamic, small-scale auroral for ms of order 100 m and less in width.