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Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter

By Tim K. Yeoman, L. J. Baddeley, R. S. Dhillon, T. R. Robinson and D. M. Wright

Abstract

HF radar backscatter which has been artificially-induced by a high power RF facility has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data, induced by the SPEAR high power radar on Svalbard, are used to investigate ULF wave processes observed by the CUTLASS HF radars. Observations are presented of both waves with a large-scale nature, driven externally to the magnetosphere and those with small azimuthal scale lengths, driven by wave-particle interactions. For ULF wave events with large azimuthal scale lengths an excellent agreement in the observed wave polarisation ellipse is found between the radar observations and ground-based magnetometer data. In contrast, for the small scale events, no ground-based magnetic counterpart is observed. Indeed the data from the two CUTLASS radars seem inconsistent, and each radar must be interpreted separately, as the spatial resolution of the radars is sufficient to resolve the wave characteristics along the radar beams, but insufficient to resolve the wave characteristics across the beams. A high azimuthal wave number (m) wave with a period of 300 s and m~−60 is observed to occur over Svalbard at ~14:00 magnetic local time. This confirms the existence of waves driven by wave-particle interactions with trapped particle populations in the outer magnetosphere. A comparison of the observed wave characteristics with previous, lower latitude, observations suggests that these high latitude waves have a similar azimuthal scale size to those generated in the inner magnetosphere; the azimuthal wave number of −60 observed in the present study is comparable to previous values of −20– −50, but suggests an increase of m with latitude. A similar energy source in drifting proton populations is also suggested, but with lower characteristic proton energies of 10 keV implicated at high latitude, compared to the 20–60 keV energies invoked for previous lower latitude observations

Publisher: Copernicus Publications on behalf of the European Geosciences Union (EGU)
Year: 2008
DOI identifier: 10.5194/angeo-26-2253-2008
OAI identifier: oai:lra.le.ac.uk:2381/8161
Journal:

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  1. (1979). A compressional Pc4 pulsation observed by three satellites in geostationary orbit near local midnight, doi
  2. (2007). A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions, doi
  3. (1976). A general approach to low-frequency instability in the ring current plasma, doi
  4. (2006). A Statistical Investigation of the Invariant Latitude Dependence of Unstable Magnetospheric Ion Populations in Relation to High m doi
  5. (1999). A statistical study of Pc 3-Pc 5 magnetic pulsations observed by the AMPTE/Ion Release Module satellite, doi
  6. (1992). A study of Pc5 hydromagnetic waves with equatorward phase propagation, doi
  7. (2001). An evaluation of range accuracy in the SuperDARN over-thehorizon HF radar systems, doi
  8. (1985). Azimuthal propagation and frequency characteristic of compressional Pc5 waves observed at geostationary orbit, doi
  9. (1983). BARS – a dual bistatic auroral radar system for the study of electric fields in the Canadian sector of the auroral zone, doi
  10. (1969). Bounce resonant interactions between pulsations and trapped particles, doi
  11. (1995). DARN/SUPERDARN A global view of the dynamics of highlatitude convection, doi
  12. (1983). First results of micropulsation activity observed by SABRE, doi
  13. HF Doppler sounder measurements of the ionospheric signatures of small scale ULF waves, doi
  14. (1997). High-latitude HF Doppler observations of ULF waves: 1. waves with large spatial scale sizes, doi
  15. (2000). High-latitude observations of ULF waves with large azimuthal wavenumbers, doi
  16. (1983). Hydromagnetic waves in the magnetosphere, in: Solar Terrestrial Physics, edited by: doi
  17. (1990). Ion flux oscillations associated with a radially polarised transverse Pc5 magnetic pulsation, doi
  18. (2006). Ionospheric Signatures of ULF Waves: Active Radar Techniques, in: Magnetospheric ULF Waves: Synthesis and New Directions, edited by doi
  19. (2001). Modeling the properties of high m Alfvén waves driven by the drift-bounce resonance mechanism, doi
  20. On the coupling between unstable magnetospheric particle populations and resonant high m ULF wave signatures in the ionosphere, doi
  21. (1983). Pc5 pulsations associated with ring current proton drifts: STARE radar observations, doi
  22. (1983). SABRE – new radar-auroral backscatter experiment, doi
  23. (2000). Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility, doi
  24. (1978). STARE: A new radar auroral backscatter experiment in northern Scandinavia, doi
  25. (1985). Statistical characteristics of Pc5 waves at geostationary orbit, doi
  26. (1991). Statistical studies of giant pulsations (Pgs): harmonic mode, doi
  27. (2004). Statistical study of unstable particle populations in the global ring current and their relation to the generation of high m ULF waves, doi
  28. (1991). Statistics of Pc5 pulsation events observed by SABRE, doi
  29. (1994). The IMAGE magnetometer network,
  30. (1976). The screening of micropulsation signals by the atmosphere and ionosphere, doi
  31. (1992). The spatial extent of radial magnetic pulsation events observed in the dayside near synchronous orbit, doi
  32. (2001). ULF waves with drift resonance and drift-bounce resonance energy sources as observed in artificially-induced HF radar backscatter, doi
  33. (2008). Yeoman et al.: Large and small scale ULF waves doi
  34. (2008). Yeoman et al.: Large and small scale ULF waves 2263 doi

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