A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HP radar

Nearly two years of 2-min resolution data and 7- to 21-s resolution data fr om the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pul sed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed i onospheric flow bursts are believed to be the ionospheric footprint of newl y reconnected geomagnetic field lines, which occur during episodes of magne tic flux transfer to the terrestrial magnetosphere - flux transfer events o r FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetar y magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurre nce rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar dat a are compared to occurrence rates and repetition frequencies of FTEs deriv ed from spacecraft data near the magnetopause reconnection region, and to g round-based optical measurements of poleward moving auroral forms, The dist ributions obtained by the various instruments in different regions of the m agnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.