Observations of Pc 1–2 waves in the outer magnetosphere

Kaye, S. M.; Kivelson, M. G.

doi:10.1029/ja084ia08p04267

Cited by 32 publications

(14 citation statements)

References 38 publications

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“…The unidirectional energy propagating away from the equatorial region was independent of event frequency or wave branch, suggesting that both the He+ and H+ wave branches do not undergo BWP propagation. Propagation away from the equator suggests that the EMIC waves were generated near the equator and propagated into higher magnetic field regions, consistent with earlier studies [e.g., Kaye and Kivelson , 1979; Fraser and Nguyen , 2001; Mursula et al , 2001].…”

Section: Discussionsupporting

confidence: 89%

Propagation of electromagnetic ion cyclotron wave energy in the magnetosphere

Loto’aniu

Fraser²,

Waters³

2005

J. Geophys. Res.

149

225

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[1] Recent satellite and conjugate observations of Pc 1 electromagnetic ion cyclotron (EMIC) waves have cast doubt on the validity of the long-standing bouncing wave packet (BWP) model that describes their propagation in the magnetosphere. A study was undertaken using the Combined Release and Radiation Effects Satellite (CRRES) E and B field data to further the understanding of the propagation characteristics of Pc 1 EMIC waves in the middle magnetosphere. CRRES covered the region L = 3.5-8.0, magnetic latitude up to ±30°, and magnetic local time 1400-0800. From 6464 hours of observation a total of 248 EMIC wave events were identified. For the first time the Poynting vector for Pc 1 EMIC waves is presented in the dynamic spectral domain permitting the study of energy propagation of simultaneous waves located in different frequency bands. The maximum wave energy flux for the events was 25 mW/m 2 , averaging range 1.3 mW/m 2 , with the direction of wave energy propagation independent of wave frequency but dependent on magnetic latitude. EMIC wave energy propagation was bidirectional both away and toward the equator, for events observed below 11°jMLatj. Unidirectional wave energy propagation away from the equator was observed for all events located above 11°j MLatj. This supports the concept of unidirectional EMIC wave energy propagation away from a broad source region centered on the geomagnetic equator. No measurable energy was observed propagating equatorward beyond the source region, in contradiction to the BWP paradigm.Citation: Loto'aniu, T. M., B.

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Section: Discussionsupporting

confidence: 89%

Propagation of electromagnetic ion cyclotron wave energy in the magnetosphere

Loto’aniu

Fraser²,

Waters³

2005

J. Geophys. Res.

149

225

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“…One study of data obtained beyond geostationary orbit supports the emphasis on low L generation. Using OGO 5 data, Kaye and Kivelson [ 1979] found that Pc 1-2 emissions were two to three times less common in the region L = 7-14 than at geosynchronous orbit, consistent with a primary source region inside L = 7. They also observed increased fluxes of low-energy (<100 eV) ions in association with their events which were attributed to encounters with detached plasma regions coincident with their events.…”

Section: Introductionmentioning

confidence: 82%

“…Since Pc 1-2 occurred for X = 0.1 -0.2 at geosynchronous orbit [Bossen et al, 1976], it was expected that events beyondL = 7 would occur below 0.1 Hz, assuming that X = 0.1 -0.2 held for the outer magnetosphere. It is interesting to note that in the 45 hours of data from local afternoon which were analyzed using the full temporal resolution of the OGO 5 magnetometer instorment (<0.144 s/sample), the occurrence of Pc 1-2 was 7% (derived from data presented by Kaye and Kivelson [ 1979]), suggesting that Pc 1-2 may have been underrepresented in the 4.6-s data. We conclude that the Kaye and Kivelson study did not examine sufficiently high frequencies.…”

Section: High L Dominancementioning

confidence: 99%

A statistical study of Pc 1–2 magnetic pulsations in the equatorial magnetosphere: 1. Equatorial occurrence distributions

Anderson¹,

Erlandson²,

Zanetti³

1992

J. Geophys. Res.

411

534

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A study of AMPTE CCE magnetic field data covering the frequency range 0.1–4.0 Hz using all data obtained during the first complete local time precession of the satellite orbit major axis (7500 hours of observations) has been made to evaluate the occurrence of transverse, narrowband Pc 1–2 emissions, identified as electromagnetic ion cyclotron (EMIC) waves, in the equatorial magnetosphere from L = 3.5 to L = 9 at all local times. We report this work in a pair of papers of which this is the first. A set of example events illustrates the pattern of Pc 1–2 occurrence: events occur primarily for L > 7, and a radial separation of several RE between low (<6) and high L (>6) pulsations is observed. Statistically, the highest concentration of events occurred near apogee in the afternoon. The L > 6 and L < 6 event populations appear to be radially separated in the morning but merge together in the afternoon. We construct a normalized occurrence distribution throughout the equatorial plane from L = 3.5 to L = 9 of Pc 1–2 with peak to peak amplitudes greater than 0.8 nT. The occurrence distribution exhibits a number of properties: for L > 7, Pc 1–2 occur at any given place in the early afternoon (1200–1500 MLT) with 10–20% probability and in the morning (0300–0900 MLT) with ≈3% probability; the L = 6–7 local time distribution reproduces results obtained previously from data at geostationary orbit; L < 5 events occur with a probability of ≤1% and a relatively uniform local time distribution. The predominance of L > 7 events implies that plasma sheet ions develop sufficient temperature anisotropy to generate EMIC waves on a routine basis in their drift from the nightside to the dayside and that plasma sheet ions on open drift paths rather than ring current ions on closed drift paths present the greatest source of equatorially generated EMIC waves. Consideration of the maximum convective growth rate of EMIC waves in a pure proton plasma versus cold plasma density and magnetic field strength illustrates how the predominance of L > 7 events and radial gap structure can be understood in terms of radial profiles of linear convective growth rates.

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“…(ii) Boundary layer A number of workers have'discussed the generation of Pct-2 waves in or near the boundary layer regions:, KAYE and KIVELSON (1979) found 11 chiefly transverse mode LH wave events in the outer magnetosphere between L = 7.1-14.2 (average frequency = 0.11 Hz) which they attributed to ICW generation near the geomagnetic equator. There was also a strong connection with enhancements in the solar wind dynamic pressure.…”

Section: Generation and Propagation Of The Emissions (I) Cuspmentioning

confidence: 99%

Multistation Observations of Pc1-2 ULF Pulsations in the Vicinity of the Polar Cusp.

Menk¹,

Fraser²,

Hansen³

et al. 1993

J. geomagn. geoelec

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Geomagnetic pulsations with frequencies in the range 0.1-2.5 Hz have been recorded with a six station Antarctic magnetometer array ranging in latitude from -62.3 to -80.6° invariant. The observed spectral characteristics were compared with the cusp and boundary layer locations for selected days in November and December, 1986, and July, 1990, in order to determine wave source regions. Specific pulsation features have been identified with different magnetospheric regions. The cusp is characterised by intense unstructured 0.15-0.45 Hz noise which diminishes rapidly away from this region. These signals are likely to result from a mixture of ion-cyclotron, Kelvin-Helmholtz and drift-wave instabilities. Narrowband unstructured Pc2 emissions typically around 0.2 Hz and short discrete Pc 1 packets or bursts with frequencies below 0.4 Hz, occur in the local morning at boundary layer latitudes, accompanied by generally enhanced power levels between about 0.1 and 0.5 Hz. These emissions are probably due to ioncyclotron waves generated near or below the He' gyrofrequency on boundary layer field lines. Propagation of such signals into the polar cap via the ionospheric waveguide is uncommon, perhaps due to the existence of severe ionospheric irregularity features near the dayside auroral oval. Structured and quasistructured emissions such as hydromagnetic chorus are recorded at the foot of plasmatrough field lines and are consistent with ion-cyclotron wave generation and propagation on closed field lines in the outer magnetosphere.

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Observations of Pc 1–2 waves in the outer magnetosphere

Cited by 32 publications

References 38 publications

Propagation of electromagnetic ion cyclotron wave energy in the magnetosphere

Propagation of electromagnetic ion cyclotron wave energy in the magnetosphere

A statistical study of Pc 1–2 magnetic pulsations in the equatorial magnetosphere: 1. Equatorial occurrence distributions

Multistation Observations of Pc1-2 ULF Pulsations in the Vicinity of the Polar Cusp.

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