B. J. Fraser , With thanks to: C. L. Waters, F. W. Menk, S. T. Ables, T. M.Loto’anui

1. Recent Developments in Magnetospheric Diagnostics using ULF Waves  B. J. Fraser, With thanks to: C. L. Waters, F. W. Menk, S. T. Ables, T. M.Loto’anui Cooperative Research Centre for Satellite Systems School of Mathematical and Physical Sciences, University of Newcastle, NSW 2308, Australia

2. Introduction • Space Weather studies in Australia are primarily undertaken within Universities and Government Agencies – There is no dedicated sponsored program. • The focus for Space Weather products is the WDC for Solar Terrestrial Science, located in the Ionospheric Prediction Service. • The Australian solar terrestrial space and atmosphere physics community is small and diverse but is making a significant contribution.

3. ULF Waves in the Earth’s Magnetosphere • Ultra-low frequency (ULF) waves in the 1 – 100 mHz frequency range are ubiquitous in the plasmasphere – magnetosphere system. • With wavelength scaling to the size of the magnetospheric cavity these waves are typically observed as standing wave resonances. • The discrete frequency maybe controlled by geomagnetic field (slow or Alfven mode) or propagate isotropically (fast mode). • ULF wave frequencies are also determined by the magnetic field strength and the (mass loaded) plasma density. • By inverting the problem, it is relatively easy to determine plasma density from observed ULF wave properties.

4. Regions of the Magnetosphere • The regions of the magnetosphere of interest to ULF wave propagation essentially on closed field lines and may be defined by the radial Alfven velocity (VA) profile. • Equatorial region (L ~ 1.5) • Low and Middle latitude region (1.5  L  5) • Plasmapause (L ~ 5) where VA maximises • High latitude plasmatrough (L  5) out to the last closed field line • The aim of this paper is to show how ULF waves may be used in different diagnostic techniques to study these four regions

5. Field Line Resonance and Cavity/Waveguide Modes Allan and Poulter, 1992

6. Alfven Velocity Profile Waters et al., 2000

7. Low and Equatorial Latitude Studies

8. FLR Latitude Location Techniques Waters, 1990

9. Cross-Phase Sounding Waters, 1990

10. Cross-Phase Sounding Waters, 1990

11. Contours of Plasma Mass Density (x10-17kg m-3) at Three Discrete Locations Along the L=1.8 Field Line Harmonic Derived Density (HARDD)Technique • Singer et al., (1981) FLR wave • equation solved generally. • Boundary value problem • using finite difference scheme. • (n+1) solution space intervals • represent n linear equations. • Plasma density completely • determined if an infinite set • of FLR harmonics available. • Optimum is 3 harmonics, • Works best at L=2-3. 2349km 4953km 4053km Price et al., 1999

12. FLR Cross-Phase at L=1.8 Price et al., 1999

13. Plasma Densities from the HARDD Method 2349km 4053km 4983km Price et al., 1999

14. Comparison of Mass Densities with Models Price et al., 1999

15. Ionospheric Dawn Along the Equator Equatorial azimuthal crossphase Modelling Waters et al., 2001

16. Plasmapause Region Studies

17. FLR at High Latitudes Waters et al., 1995

18. CANOPUS-CRRES Intercalibration Loto’anui et al., 1999

19. CANOPUS-CRRES Intercalibration Loto’anui et al., 1999

20. CANOPUS-CRRES Intercalibration Loto’anui et al., 1999

21. CANOPUS-CRRES Intercalibration Loto’anui et al., 1999

22. CANOPUS-CRRES Intercalibration Loto’anui et al., 1999

23. Plasma Mass Density 94-10-01 94-10-02 94-10-03 94-10-04 94-10-05 94-10-06 Waters, 1998

24. Cross- Phase Spectra L=5.75 IMAGE; SAMNET ground data L=4.75 Waters, 2000

25. High Latitude Australian Research Also Macquarie Island L~4

26. Four Days of Increasing Activity: Davis-Zhong Shan, Antarctica Power Density Pol’n Xphase Pwr ratio

27. Australian Close-Spaced Network Antarctica Phase closure used Ables et al., 1998

28. Pc5 ULF Wave Conjugate Phase Properties

29. Conjugate Cross-Phase Davis -Longyearbyen Kp=17 Kp=13 Kp=10 Kp=32 Ables et al., 2000

30. LYR-Conjugate and IMF By Variation Pc5 phase (DAV, ZHS, MAW, LYR) T96 Model Liu et al., 2002 (submitted)

31. Summary and Conclusions • ULF waves provide a simple and cheap but powerfu method to monitor the closed field line region of the plasmasphere-magnetosphere system. • The techniques rely on resonance and in particular phaseobservations, which provide information on the cavity size and boundary location. • Assumptions of plasma distribution and geomagnetic field models allow plasma mass density to be determined. • Particular areas of application of importance in studying the dynamics of the near-Earth space plasma include: • Dawn and Dusk equatorial ionospheric effects • Plasma mass density measurements in the plasmasphere and magnetosphere • Monitoring the dynamics of the plasmapause and open-closed boundary regions • Conjugate point field line tracing. • The techniques generally depend on magnetic field and plasma density distribution models. If harmonics are present then the HARRD method may be applied. (No density model assumption). • These methods will be useful for comparing with and calibrating IMAGE data.

32. THE END

33. Ionospheric Mass Loading Poulter et al. 1988