Electromagnetic Ion Cyclotron Waves in the Magnetosphere Wave

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 REPW-07

Outline 1. What is the plasmapause? 2. EMIC wave propagation – magnetosphere & ionosphere 3. EMIC waves seen in association with plasma plumes 4. Plasma-Ring Current conditions associated with EMIC waves occurring in plasmasphere & plume 5. Wave & plasma Statistics REPW-07

1. What is Your Plasmapause? Do all Instruments see the Same Plasmapause? “Cold” plasma measured? OGO-5 DE-1 CRRES Cluster H+ H+, He+, O+ ee-, ions Heavy Ions in the Plasmasphere DE-1 (Horwitz et al. , GRL, 1984) REPW-07 LANL POLAR ULF Waves IMAGE Plasmasphere/Plumes Ions e-, ions Ion Mass He+, Ion Mass Loading DE-1 (Fraser et al. , GRL, 2005)

2. EMIC Wave Propagation: Dispersion in a 3 -ion Cold Plasma Fraser, 1985 ATS-6 Fraser & Mc. Pherron 1982 REPW-07

EMIC Wave Propagation Away from the Equator (Perraut et al. , JGR, 1984) REPW-07

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 REPW-07

Electromagnetic Ion Cyclotron Waves and Plasma Diagnostics in the Magnetosphere EMIC Waves Seen as Pc 1 -2 Waves at High Latitudes on the Ground REPW-07

Bouncing Wave Packets - Ground Observations Upper Panel: A superimposed dynamic spectrum of Pc 1 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). REPW-07

CRRES Observations ·EMIC waves at 2 -3 Hz seen at L=4. 5 -5. 5 and MLAT=27 o off the equator (no fine structure) ·Propagated from the equatorial region ·Occurs in the trough region and runs into the plasmapause REPW-07 f. He+ Plasmapause

CRRES Observations ·EMIC event frequency 0. 3 -1. 5 Hz at L=5. 3 and MLAT=0. 5 o ·Propagation in the plasmasphere with density Ne=100 cm-3 Azimuth Ellipticity BH ·Harmonic structure with fundamental below f. He+ and three harmonics above ·Propagation in a density slot where Ne reduces from 100 cm-3 to ~70 cm-3 minimum in the duct ·Width of duct is ~0. 16 Re, REPW-07 (N + ½) waves

3. EMIC Waves and Radial Plasma Structures G 8 G 10 Full plasmasphere EMIC in Plume 18: 20 -20: 00 UT G 8 21: 00 -24: 00 UT G 10 EMIC at Plume edge? Radial Plumes 21: 35 -22: 20 UT G 8 REPW-07 Maps from: Spasojevic et al. (2003) (Fraser et al. , 2005)

EMIC Waves appearing in Plumes 9 June 2001 Hn G 10 Frequency 1. 0 0 21 12 Hn G 8 10 June 2001 1. 0 Hn G 8 Frequency 1. 0 24 UT 15 LT • GOES can only see waves with frequencies <1 Hz. • EMIC waves identified through wave analysis. • Typically similar to IPDP and Pc 1 -2 • Unstructured pulsations seen in the Outer magnetosphere and on the Ground at high latitudes (Anderson et al 1996; Menk et al 1992) 0 18 13 REPW-07 22 UT 17 LT 0 21: 30 16: 30 22: 30 UT 17: 30 LT

23 May 2001 IMAGE FUV-EUV Detached Proton Arc; Plasma Plume FUV sees arcs 1901 -2327 UT (T. Immel) GOES-8 Footprint (T 89 Kp=3) EUV plasmasphere (J. Goldstein) REPW-07 GOES EMIC waves

GOES-8 EMIC Waves 23 May 2001 Note He+ slot 1. 0 Hn Hz 0 2210 REPW-07 2310 UT

GOES-8 Spectral Analysis: 23 May 2001 2210 -2310 UT He-Hn He Pwr 1. 0 Coherence Hn 0 LH Pwr Crossphase 0 0 1. 0 Frequency (Hz) REPW-07 RH 0 Frequency (Hz) 1. 0

GOES – LANL (MPA) – IMAGE (EUV) 23 -24 May 2001 EUV REPW-07 EUV

4. Ring Current – Plasmapause Interaction for EMICW Plasmasphere-ring current interaction at the plasmapause L=4 -5 (Kawamura et al. , Mem. , NIPR, 1982) REPW-07 (Summers et al. , JGR, 1998) 17 April, 2002 (Goldstein et al. , JGR, 2005)

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. REPW-07

3. Occurrence of EMIC Waves at CRRES: 14 months 1990 -1991 More waves occurring outside the Plasmapause below f. He+ Normalised wave frequency - L f. He+ L = 0 is the plasmapause. L < 0 waves in the plasmasphere L > 0 waves outside the plasmasphere, in the plasma trough. REPW-07

Plasma “Cavity”- Plasmapause-Plasma Trough A B C D REPW-07

Plasmasphere-Plasmapause-Plasma Plumes 18 D C Geostationary orbit (GOES, LANL) GTO orbit (CRRES) L=7 B 4 12 A 06 REPW-07

6. Plasmaspheric Plumes and EMIC Waves Following a Storm CRRES 9 September, 1991 • Orbits separated by ~10 hr • 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 REPW-07 (Density from Moldwin et al. , 2003)

CRRES Orbit 991 9 September 1991 IMF Bz ~ – 5 n. T REPW-07

CRRES Orbit 992 9 -10 September 1991 IMF Bz ~ – 10 n. T REPW-07

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 -60 ke. V protons 17 April, 2002 REPW-07 (Goldstein et al. , JGR, 2005)

EMIC Waves and Plasma Gradients 18 Azimuthal Gradient Convection Radial Gradient 12 L=7 Corotation REPW-07 06

5. Statistics: Plasma Conditions for Plumes CRRES - Normalised frequency – PWE e- density CRRES - Frequency – MLT REPW-07

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) REPW-07

CRRES Statistics - 1 Normalised frequency - MLAT Normalised frequency - L 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. REPW-07

CRRES Statistics - 2 • Scatter plot of CRRES EMIC wave event local magnetic field magnitude against plasma density. • Overlaid are contour plots of maximum convective growth rate for a pure proton plasma in the N–B plane generated by Anderson et al. JGR, (1992). He+ Scatter plot of the wave transverse spectral power density versus ΔL = Le − Lpp where Le and Lpp are the L values corresponding to the position of the wave occurrence and that of the REPW-07 plasmapause, respectively. O+ Scatter plot of the wave frequency versus local total magnetic field

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+) REPW-07

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………… REPW-07