SuperDARN Measurements

of Double-Peaked Velocity Spectra

Abstract

The SuperDARN HF radars in Saskatoon, Sask. and Kapuskasing, Ont. have been used to measure Doppler velocity spectra of backscatter from the F-layer. A special multipulse sequence was developed to increase the number of measured autocovariance points. These spectra were used to benchmark spectral estimators based on the Fourier Transform and parametric spectral estimators. A parametric spectral estimator using the Burg algorithm improved the resolution of the spectra. A distinct double-peaked spectral signature was found in spatially localized regions. A comparison with particle data as measured by a DMSP satellite suggests a strong spatial correlation of soft-electron precipitation with great variability with the occurrence of the spectral features. Several generating mechanisms for double-peak spectra are suggested, including the Kelvin-Helmholtz instability and precipitation-induced electric fields in arc and ray structures.

Acknowledgements

I would like to thank Dr. G. Sofko for supporting me financially and academically throughout my graduate career at the University of Saskatchewan and during the making of this thesis. He has made it possible for me to pursue an academic career in Canada after my undergraduate years were completed and he has given me much freedom during my graduate work.

I would also like to thank all the members of the SuperDARN team here in Saskatoon for their generous supply of help, advice and encouragement that is so much needed for a graduate student. I hope to give something back to them with this thesis.

Finally, I would like to thank my wife Jennifer for putting up with my continued urge to explain all the details of my research to her -- it has helped me focus and hopefully do a better job.

Index

• Roadmap for this Thesis
• Physics of the Ionosphere
  • Basic Properties of the Earth's Magnetosphere
    • The Solar Wind
    • The Geomagnetic Cavity
    • Circulation Patterns, Currents and Electric Fields
  • Magneto-ionic Theory and the Appleton-Hartree Equation
  • Refraction of an HF Radio Wave in the Ionosphere
  • Instabilities
    • Farley-Buneman Instability
    • Gradient Drift Instability
    • Kelvin-Helmholtz Instability
    • Instabilities Generated by Thermal Sources
• The SuperDARN HF radar
  • Coherent Scatter Radar and the Scatter Theorem
  • Introduction to SuperDARN
  • Operation of the Radar
    • Normal Operation
    • ACF Determination
      • Double-Pulse
  • Pulse Pattern Optimization
    • Double pulses with variable lag
    • Multipulse
  • Analysis of the Data
    • Normal ACF analysis using a Phase Fit
    • Power Spectrum Analysis using Spectral Estimators
• The DMSP F12 Satellite
  • The DMSP Satellite and the SSJ/4 Particle Analyzer
  • Analysis of the Particle Data
    • The AAGCM Coordinate System
    • Conductivity Estimation
    • Ionization Rate Estimation
• Experimental Results
  • Observation Periods
  • High-Resolution Autocorrelation Functions
  • Doppler-velocity Spectra with Two Close Peaks
  • Morphology during a Complete Scan
    • SuperDARN Maps of Double-peaked Doppler Velocity Spectra
    • 1 Jan/95, 16:21 - 16:23 UT
    • 6 Jan/95, 17:03 - 17:05 UT
    • 16 Jan/95, 16:45 - 16:47 UT
    • 26 Jan/95, 16:27 - 16:29 UT
    • 28 Jan/95, 2:13 - 2:15 UT
    • 18 Feb/95, 1:25 - 1:27 UT
    • 20 Feb/95, 16:32 - 16:34 UT
    • 21 Feb/95, 2:30 - 2:32 UT
    • 25 Feb/95, 1:42 - 1:44 UT
• Discussion
• Conclusion and Summary
• References
• Computer Programs
  • Multipulse Sequencer
  • SuperDARN Autocovariance Function Processing Tools
  • DMSP SSJ/4 Data Analysis and Processing
• Acronyms
• About this document ...