Brian Fraser Centre for Space Physics, University of Newcastle , Callaghan, NSW , Australia

1. Electromagnetic Ion Cyclotron Waves in the Magnetosphere: Wave and Plasma Properties Brian Fraser Centre for Space Physics, University of Newcastle , Callaghan, NSW, Australia With contributions from: Jerry Goldstein, Tom Immel, Paul Loto’aniu, Nigel Meredith, Mark Moldwin, Howard Singer, Michelle Thomsen

2. Outline • What is the plasmapause? • EMIC wave propagation – magnetosphere & ionosphere • EMIC waves seen in association with plasma plumes • Plasma-Ring Current conditions associated with EMIC waves occurring in plasmasphere & plume • Wave & plasma Statistics

3. 1. What is Your Plasmapause? Do all Instruments see the Same Plasmapause? “Cold” plasma measured? OGO-5 H+ DE-1 H+,He+,O+ CRRES e- Cluster e-, ions LANL Ions POLAR e-, ions ULF Waves Ion Mass IMAGE - Plasmasphere/Plumes He+, Heavy Ions in the Plasmasphere Ion Mass Loading DE-1 DE-1 (Horwitz et al., GRL, 1984) (Fraser et al., GRL, 2005)

4. 2. EMIC Wave Propagation: Dispersion in a 3-ion Cold Plasma Fraser, 1985 ATS-6 Fraser & McPherron 1982

5. EMIC Wave Propagation Away from the Equator (Perraut et al., JGR, 1984)

6. Propagation away from a Source Region Within ±110 of the Magnetic Equator CRRES Poynting vector Data N. Hemisphere     S. Hemisphere Loto’aniu et al., 2005

7. Electromagnetic Ion Cyclotron Waves and Plasma Diagnostics in the Magnetosphere EMIC Waves Seen as Pc1-2 Waves at High Latitudes on the Ground

8. Bouncing Wave Packets - Ground Observations Upper Panel: A superimposed dynamic spectrum of Pc1 EMIC waves observed at the near-conjugate stations of Great Whale River and Byrd. The solid and dotted arrows represent signals observed at these two stations respectively. Lower panel: Amplitude records of the wave structure illustrating the 180 phase shift between hemispheres (after Saito, 1969).

9. CRRES Observations • EMIC waves at 2-3Hz seen at L=4.5-5.5 and MLAT=27o off the equator (no fine structure) • Propagated from the equatorial region • Occurs in the trough region and runs into the plasmapause fHe+ Plasmapause

10. Azimuth Ellipticity BH CRRES Observations • EMIC event frequency 0.3-1.5Hz at L=5.3 and MLAT=0.5o • Propagation in the plasmasphere with density Ne=100cm-3 • Harmonic structure with fundamental below fHe+ and three harmonics above • Propagation in a density slot where Ne reduces from 100cm-3 to ~70cm-3 minimum in the duct • Width of duct is ~0.16Re, (N + ½) waves

11. 3. EMIC Waves and Radial Plasma Structures G8 G10 18:20-20:00UT G8 21:00-24:00UT G10 21:35-22:20UT G8 Maps from: Spasojevic et al. (2003) Full plasmasphere EMIC in Plume EMIC at Plume edge? Radial Plumes (Fraser et al., 2005)

12. EMIC Waves appearing in Plumes 9 June 2001 G10 1.0 Hn Frequency 0 21 24UT 12 15LT 10 June 2001 G8 G8 1.0 1.0 Hn Hn Frequency 0 0 18 22UT 21:30 22:30UT 13 17LT 16:30 17:30LT • GOES can only see waves • with frequencies <1Hz. • EMIC waves identified through • wave analysis. • Typically similar to IPDP and Pc1-2 • Unstructured pulsations seen in the • Outer magnetosphere and on the • Ground at high latitudes • (Anderson et al 1996; Menk et al 1992)

13. 23 May 2001 IMAGE FUV-EUV Detached Proton Arc; Plasma Plume FUV sees arcs 1901-2327UT (T. Immel) GOES-8 Footprint (T89 Kp=3) EUV plasmasphere (J. Goldstein) GOES EMIC waves

14. GOES-8 EMIC Waves 23 May 2001 Note He+ slot 1.0 Hn Hz 0 2210 2310UT

15. GOES-8 Spectral Analysis: 23 May 2001 2210-2310UT He-Hn He Pwr Pwr 1.0 Coherence Hn 0 Pwr LH 0 RH Crossphase 0 1.0 1.0 0 Frequency (Hz) Frequency (Hz)

16. GOES – LANL (MPA) – IMAGE (EUV) 23 -24 May 2001 EUV EUV

17. 4. Ring Current – Plasmapause Interaction for EMICW Plasmasphere-ring current interaction at the plasmapause L = 4 - 5 (Summers et al., JGR, 1998) (Kawamura et al., Mem., NIPR, 1982) 17 April, 2002 (Goldstein et al., JGR, 2005)

18. Occurrence of EMIC Waves at CRRES: 14 months 1990-1991 Reasonably even distribution with L over X<0.25 Normalised wave frequency - L L = 0 is the plasmapause. L < 0 waves in the plasmasphere L > 0 waves outside the plasmasphere, in the plasma trough. 

19. 3. Occurrence of EMIC Waves at CRRES: 14 months 1990-1991 More waves occurring outside the Plasmapause below fHe+ Normalised wave frequency - L fHe+ L = 0 is the plasmapause. L < 0 waves in the plasmasphere L > 0 waves outside the plasmasphere, in the plasma trough. 

20. Plasma “Cavity”- Plasmapause-Plasma Trough A B C D

21. Plasmasphere-Plasmapause-Plasma Plumes 18 D C Geostationary orbit (GOES, LANL) GTO orbit (CRRES) B 4 L=7 12 A 06

22. 6. Plasmaspheric Plumes and EMIC Waves Following a Storm CRRES 9 September, 1991 • Orbits separated by ~10hr • Orbits at same MLT’s • SSC occurred at end • of orbit 990 • Orbits 991-992 in • recovery phase • Plume evolution and • EMIC wave association • EMIC at steep • gradients/edges? EMIC (Density from Moldwin et al., 2003)

23. CRRES Orbit 991 9 September 1991 IMF Bz ~ –5nT

24. CRRES Orbit 992 9-10 September 1991 IMF Bz ~ –10nT

25. 6. Ring Current – Plasmasphere Interaction for EMICW Radial plasmasphere-ring current interaction at the plasmapause (Kawamura et al., Mem., NIPR, 1982) Azimuthal plasmasphere-ring current interaction with plumes HENA 10-60keV protons 17 April, 2002 (Goldstein et al., JGR, 2005)

26. EMIC Waves and Plasma Gradients 18 Azimuthal Gradient Convection Radial Gradient 12 L=7 Corotation 06

27. 5. Statistics: Plasma Conditions for Plumes CRRES - Normalised frequency – PWE e- density  CRRES - Frequency – MLT

28. Occurrence of EMIC Waves at CRRES: 14 months 1990-1991 More waves seen 14-18 MLT and L > 4 8 4 (Meredith et al., JGR, 2003)

29. CRRES Statistics - 1 Normalised frequency - L Normalised frequency - MLAT Ellipticity - MLAT Normalised frequency – e- density RH LH Normalised wave frequency - L L = 0 is the plasmapause. L < 0 waves in the plasmasphere L > 0 waves outside the plasmasphere, in the plasma trough. 

30. CRRES Statistics - 2 • Scatter plot of CRRES EMIC wave event local magnetic field magnitude against plasma density. • Overlaid are contourplots of maximum convective growth rate for a pureproton plasma in the N–B plane generated by Anderson et al. JGR,(1992). He+ Scatter plot of the wave transverse spectral power densityversus ΔL = Le − Lpp where Le and Lpp are the L valuescorrespondingto the position of the wave occurrence and that of theplasmapause, respectively. O+ Scatter plot of the wave frequency versus local total magnetic field magnitude.

31. Summary • EMIC waves occur more often in the plasma trough than the plasmasphere/plasmapause • They preferentially occur in association with the higher density regions • The high density regions may be radially structured plumes (or a full plasma trough) • A gradient interface boundary between the ring current and the cold/cool plasma may be necessary to create instability. This may be: • A radial boundary in the trough produced by plumes, or • An azimuthal boundary provided by the plasmapause • There may be a threshold density for instability, in the range 10-100 cm-3. (Role of plasma ß?) • NOTE: Identification of the plasmapause may depend on particle species(e-, H+, He+, O+)

32. What Needs to be Done? • Robust EMIC wave statistics taking into consideration Solar Wind & IMF conditions, and Dst, Kp, AE etc. • Undertake similar E-field EMIC wave analysis. Will see EMIC at low L. Not possible with B field due to steep gradient at low L. • Individual storm event studies for comparison with modellers. Do for both RC and RB. (New GOES data Available) • What else does the RB community want from the CRRES dataset? Important Unresolved Issues • Are EMIC waves seen during the main phase • Role of Magnetosonic waves (first few harmonics only) • As yet to be defined…………