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A quantitative analysis of the diurnal evolution of Ionospheric Alfven resonator magnetic resonance features and calculation of changing IAR parameters

By S. R. Hebden, T. R. Robinson, D. M. Wright, Tim K. Yeoman, T. Raita and T. Bosinger

Abstract

Resonance features of the Ionospheric Alfvén Resonator (IAR) can be observed in pulsation magnetometer data from Sodankylä, Finland using dynamic spectra visualizations. IAR resonance features were identified on 13 of 30 days in October 1998, with resonance structures lasting for 3 or more hours over 10 intervals. The diurnal evolution of the harmonic features was quantified for these 10 intervals using a manual cursor-clicking technique. The resonance features displayed strong linear relationships between harmonic frequency and harmonic number for all of the time intervals studied, enabling a homogeneous cavity model for the IAR to be adopted to interpret the data. This enabled the diurnal variation of the effective size of the IAR to be obtained for each of the 10 time intervals. The average effective size was found to be 530 km, and to have an average variation of 32% over each time interval: small compared to the average variation in Alfvén velocity of 61%. Thus the diurnal variation of the harmonics is chiefly caused by the changing plasma density within the IAR due to changing insolation. This study confirms Odzimek (2004) that the dominating factor affecting the IAR eigenfrequencies is the variation in the Alfvén velocity at the F-layer ion-density peak, with the changing IAR size affecting the IAR eigenfrequencies to a smaller extent. Another IAR parameter was derived from the analysis of the IAR resonance features associated with the phase matching structure of the standing waves in the IAR. This parameter varied over the time intervals studied by 20% on average, possibly due to changing ionospheric conductivity

Topics: Ionosphere (Auroral ionosphere;Wave propagation), Radio science (Electromagnetic noise and interference)
Publisher: European Geosciences Union (EGU), Copernicus Publications,. Springer Verlag (Germany)
Year: 2005
DOI identifier: 10.5194/angeo-23-1711-2005
OAI identifier: oai:lra.le.ac.uk:2381/711

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Citations

  1. (1984). A.: An Introduction to the Analysis and Processing of Signals, doi
  2. (2003). Detection of artificially generated ULF waves by the FAST spacecraft and its application to the “tagging” of narrow fluw tubes, doi
  3. (1987). Discovery of resonance structure in the spectrum of atmospheric electromagnetic background noise in the range of shortperiod geomagnetic pulsations, doi
  4. (2002). Electron acceleration observed by the FAST satellite within the IAR during a 3 Hz modulated EISCAT heater experiment, doi
  5. (2000). Excitation of Alfve´n waves and vortices in the ionospheric Alfve´n resonator by modulated powerful radio waves, doi
  6. (2000). FAST observations of ULF waves injected into the magnetosphere by means of modulated RF heating of the auroral electrojet, doi
  7. (1991). Feedback instability of the Ionospheric Resonant cavity, doi
  8. (1996). Ground-based observations of ionospheric Alfve´n resonator bands,
  9. (1981). Ionospheric Alfve´n resonator,
  10. Ionospheric modification experiments in northern Scandinavia, doi
  11. (2000). Modelling the diurnal evolution of the resonance spectral structure of the atmospheric noise background in the Pc1 frequency range, doi
  12. (2003). Morphology of the spectral resonance structure of the electromagnetic background noise in the range of 0.1–4 Hz at L=5.2, doi
  13. (1976). On properties of an ionospheric Alfve´n resonator,
  14. (1985). Solar cycle variations in the ionospheric Alfve´n resonator doi
  15. (1985). The EISCAT Ionospheric Radar: the System and its Early Results,
  16. (1998). The Fast Auroral SnapshoT doi
  17. (1990). The Ionospheric Alfve´n resonator, doi

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