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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

Electromagnetic Ion Cyclotron Electromagnetic Ion Cyclotron Waves in the Magnetosphere: Waves in the Magnetosphere: Wave and Plasma PropertiesWave and Plasma Properties

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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

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Heavy Ions in the Plasmasphere Ion Mass Loading

(Horwitz et al., GRL, 1984) (Fraser et al., GRL, 2005)

1. What is Your Plasmapause?Do all Instruments see the Same Plasmapause?

OGO-5 H+

DE-1 H+,He+,O+

CRRES e-

Cluster e-, ions

LANL IonsPOLAR e-, ionsULF Waves Ion MassIMAGE -Plasmasphere/Plumes He+,

“Cold” plasma measured?

DE-1 DE-1

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2. EMIC Wave Propagation:Dispersion in a 3-ion Cold Plasma

ATS-6

Fraser & McPherron 1982

Fraser, 1985

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EMIC Wave Propagation Away from the Equator

(Perraut et al., JGR, 1984)

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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

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Electromagnetic Ion Cyclotron Waves and Plasma Electromagnetic Ion Cyclotron Waves and Plasma

Diagnostics in the MagnetosphereDiagnostics in the MagnetosphereEMIC Waves Seen as Pc1-2 Waves

at High Latitudes on the Ground

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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).

Bouncing Wave Packets - Ground Observations

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Plasmapause

·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

CRRES Observations

fHe+

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BH

Ellipticity

Azimuth

·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,

CRRES Observations

(N + ½) waves

REPW-07 Maps from: Spasojevic et al. (2003)

G8G10

18:20-20:00UT G821:00-24:00UT G10

21:35-22:20UT G8

3. EMIC Waves and Radial Plasma Structures

(Fraser et al., 2005)

Full plasmasphere

Radial Plumes

EMIC in Plume

EMIC at Plume edge?

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9 June 2001

10 June 200121 24UT

18 22UT13 17LT

12 15LT

G10

G8 G8

21:30 22:30UT16:30 17:30LT

Hn

Hn Hn

Fre

quen

cy

Fre

quen

cy

0

1.0 1.0

0

0

1.0

EMIC Waves appearing in Plumes•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)

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23 May 2001 IMAGE FUV-EUVDetached Proton Arc; Plasma Plume

GOES-8 Footprint (T89 Kp=3)

FUV sees arcs 1901-2327UT(T. Immel)

EUV plasmasphere(J. Goldstein)

GOES EMIC waves

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GOES-8 EMIC WavesGOES-8 EMIC Waves 23 May 2001 23 May 2001Note HeNote He++ slot slot

2210 2310UT

0

1.0

Hz

Hn

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He

Hn

He-Hn

Coherence

Crossphase

0 1.00 1.0

Pwr

Pwr

Pwr

0

1.0

LH

0

RH

Frequency (Hz) Frequency (Hz)

GOES-8 Spectral Analysis: 23 May 2001GOES-8 Spectral Analysis: 23 May 20012210-2310UT2210-2310UT

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EUV EUV

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

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4. Ring Current – Plasmapause Interaction for EMICW

(Kawamura et al., Mem., NIPR, 1982)

(Goldstein et al., JGR, 2005)

Plasmasphere-ring current interaction at the plasmapauseL = 4 - 5

17 April, 2002

(Summers et al., JGR, 1998)

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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. 

Occurrence of EMIC Waves at CRRES:

14 months 1990-1991

Reasonably even distribution with L over X<0.25

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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. 

3. Occurrence of EMIC Waves at CRRES:

14 months 1990-1991

fHe+

More waves occurring outside the Plasmapause below fHe+

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A BC

D

Plasma “Cavity”- Plasmapause-Plasma Trough

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L=74

06

18

12

Plasmasphere-Plasmapause-Plasma Plumes

Geostationary orbit(GOES, LANL)

GTO orbit(CRRES)

A

B

CD

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6. Plasmaspheric Plumes and EMIC Waves Following a Storm CRRES 9 September, 1991

EMIC

(Density from Moldwin et al., 2003)

•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?

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

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

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6. Ring Current – Plasmasphere Interaction for EMICW

(Kawamura et al., Mem., NIPR, 1982)

Azimuthal plasmasphere-ring current interaction with plumes

(Goldstein et al., JGR, 2005)

Radial plasmasphere-ring current interaction at the plasmapause

17 April, 2002

HENA 10-60keV protons

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L=7

18

12

06

EMIC Waves and Plasma Gradients

Radial Gradient

Azimuthal Gradient

Convection

Corotation

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CRRES - Normalised frequency – PWE e- density

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20 25 30

MLT (Hr)

Fre

qu

en

cy

(H

z)

CRRES - Frequency – MLT

5. Statistics: Plasma Conditions for Plumes

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Occurrence of EMIC Waves at CRRES:14 months 1990-1991

(Meredith et al., JGR, 2003)

4

8

More waves seen 14-18 MLT and L > 4

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CRRES Statistics - 1Normalised frequency - L Normalised frequency - MLAT

Normalised frequency – e- density

Normalised wave frequency - L

Ellipticity - MLAT

L = 0 is the plasmapause. L < 0 waves in the plasmasphere L > 0 waves outside the plasmasphere, in the plasma trough. 

RH

LH

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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 plasmapause, respectively.

Scatter plot of the wave frequency versus local total magnetic field magnitude.

O+

He+

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).

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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+)

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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…………