High-latitude observations of impulse-driven ULF pulsations in the ionosphere and on the ground

摘要: Abstract. We report the simultaneous observation of 1.6–1.7 mHz pulsations in ionospheric F-region with CUTLASS bistatic HF radar and an Doppler sounder, on ground IMAGE SAMNET magnetometer arrays, upstream solar wind. was at time being operated a special mode optimized for high resolution studies ULF waves. A novel use is made returns to detect signature The were initiated by strong, sharp decrease wind dynamic pressure near 09:28 UT 23 February 1996, persisted some hours. They observed magnetometers over 20° latitude, coupling field line resonance 72° magnetic latitude. had azimuthal m numbers ~ -2, consistent propagation away from noon sector. radars show transient velocity flows cusp auroral zones, poleward resonance, small amplitude oscillations across widely spaced regions lower latitudes. latter detected scatter also vertical incidence sounder. Their order ± 10 ms-1. similar perturbation frequency present recorded WIND spacecraft. initial associated cosmic noise absorption imaging riometer 66° observations suggest that perturbations or IMF result fast compressional waves propagate through magnetosphere drive forced resonant geomagnetic lines. wave may stimulate perturbations. demonstrate contain important information small-amplitude features, extending scope capability these track features ionosphere. Key words. Ionosphere (Ionosphere-magnetosphere interactions; disturbances) – Magnetospheric physics (MHD instabilities)