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A quantitative study of observations of the\udionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a\udhigh-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has\udbeen undertaken. The signatures, which are clearly correlated with pulsations in\udground magnetometer data, exhibit periods in the range 100–400 s and have\udazimuthal wave numbers in the range 3–8. They are interpreted here as local\udfield line resonances. Phase information provided by O- and X-mode Doppler data\udsupport the view that these are associated with field line resonances having\udlarge azimuthal scale sizes. The relative phases and amplitudes of the\udsignatures in the Doppler and ground magnetometer data are compared with a model\udfor the generation of Doppler signatures from incident ULF waves. The outcome\udsuggests that the dominant mechanism involved in producing the Doppler signature\udis the vertical component of an E × B bulk\udmotion of the local plasma caused by the electric field perturbation of the ULF\udwave. Key words. Auroral ionosphere ·\udMagnetosphere-ionosphere interactions · MHD waves and instabilities HF Doppler\ud· ULF Wave

High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes