Quiettime observation of a coherent compressional Pc-4 micropulsation at synchronous altitude

Barfield, J. N.; Lanzerotti, L. J.; Maclennan, C. G.; Paulikas, G. A.; Schulz, Michael

doi:10.1029/ja076i022p05252

Cited by 39 publications

(9 citation statements)

References 19 publications

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“…Because the field line displacement is not a directly measurable quantity, one determines its symmetry from the associated magnetic field perturbation. An equatorial compressional Pc 4 wave observed by the ATS I geostationary satellite (magnetic latitude ~ 2 ø) exhibited properties similar to those reported by Hillebrand et al [1982], but whether the pulsation was a giant pulsation has not been discussed [Barfield et al, 1971;Lanzerotti and Tartaglia, 1972]. At the equator, for example, an odd-mode wave has a node of the transverse component and an antinode of the compressional component.…”

supporting

confidence: 54%

On the standing wave mode of giant pulsations

Takahashi¹,

Sato²,

Warnecke³

et al. 1992

J. Geophys. Res.

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Both odd‐mode and even‐mode standing wave structures have been proposed for giant pulsations. Unless a conclusion is drawn on the field‐aligned mode structure, little progress can be made in understanding the excitation mechanism of giant pulsations. In order to determine the standing wave mode, we have made a systematic survey of magnetic field data from the AMPTE CCE spacecraft and from ground stations located near the geomagnetic foot point of CCE. We selected time intervals when CCE was close to the magnetic equator and also magnetically close to Syowa and stations in Iceland, and when either transverse or compressional Pc 4 waves were observed at CCE. Magnetograms from the ground stations were then examined to determine if there was a giant pulsation in a given time interval. One giant pulsation was associated with a compressional wave, while no giant pulsation was observed in association with transverse wave events. The CCE magnetic field record for the giant pulsation exhibited a remarkable similarity to a giant pulsation observed from the ATS 6 geostationary satellite near the magnetic equator (Hillebrand et al., 1982). In agreement with Hillebrand et al., we conclude that the compressional nature of the giant pulsation is due to an odd‐mode standing wave structure. This conclusion places a strong constraint on the generation mechanism of giant pulsations. In particular, if giant pulsations are excited through the drift bounce resonance of ions with standing Alfvén waves, ω ‐ mωd = ±Nωb, where ω is the wave frequency, m is the azimuthal wave number, ωd is the ion drift frequency, N is an integer, and ωb is the ion bounce frequency, then the resonance must occur at an even N.

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supporting

confidence: 54%

On the standing wave mode of giant pulsations

Takahashi¹,

Sato²,

Warnecke³

et al. 1992

J. Geophys. Res.

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“…However, if the perpendicular energy flow does exist, and it seems quite likely in the actual case, as pulsations are found down to low L values, the total power can be estimated. Ea = 4 mV/m and B• = 4 nT give a mean power density of 6 x 10 -• W/m 2, and if the area at geosynchronous distance, over which the wave is found, is roughly set to 6 x 10 a½ m •, equivalent to a belt at the equatorial plane extending, for example, 20 ø in latitude and 5 hours in longitude, we obtain a total power of 3.6 x 10 9 W. This is a considerable but not unrealistically large quantity and is comparable to results given by Greenwald and Walker [1980], who calculate a power dissipation from the wave field in a magnetospheric storm to be 6 x 109 W. Barfield et al [ 1971].…”

Section: Satellite Observationssupporting

confidence: 83%

Simultaneous observations of a pulsation event from the ground, with balloons and with a geostationary satellite on August 12, 1978

et al. 1984

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A pulsation event with a period of 6–8 min has been observed simultaneously by the geostationary satellite GEOS 2 and two balloons located in the area magnetically conjugate to the satellite. The balloons were equipped with electric field and X ray instruments. The pulsation event occurred in the magnetic local time sector 0600–1100 determined by ground‐based measurements. The satellite instruments observed the signature of a magnetosonic wave having a radially inward directed Poynting vector. The electric field associated with the wave was closely correlated with the electric field detected by the balloon instrument near the footprint of the magnetic field line through GEOS 2. The ground‐based observations show that the wave phase pattern was north‐south striated and that it moved from east to west. The balloon X ray measurements showed a strongly pulsating particle precipitation, in close correlation with the intensity of the energetic electron flux and the VLF electromagnetic radiation measured on the satellite, suggesting a wave‐particle interaction process. The pulsations seem to originate beyond the geosynchronous orbit. The study demonstrates the usefulness of simultaneous measurements with a geostationary satellite and instruments in the ground area magnetically conjugate to the satellite.

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“…On the other hand, the micropulsations observed on the ground are mostly torsional (Saito, 1969). A recent satellite observation by ATS-1 has, however, shown that a pure compressional oscillation of a period around 2 rain were observed which was observed at College, Alaska as a pure torsional oscillation (Barfield et al, 1971). There should exist some mode conversion from a compressional mode to a torsional one in somewhere.…”

Section: Discussionmentioning

confidence: 99%

Interrelation between VLF and ULF emissions

Kimura

1974

Space Sci Rev

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Observations and theoretical works so far made are reviewed in regard to the interrelation of VLF and ULF emissions. Quasi-periodic VLF emissions are one of the typical examples showing the interrelation between the two phenomena. The term 'modulation' may be more appropriate to explain these phenomena. Tentative interpretations will be given of the VLF and ULF emissions which are closely associated through a modulation of the electron distributions.

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Quiettime observation of a coherent compressional Pc-4 micropulsation at synchronous altitude

Cited by 39 publications

References 19 publications

On the standing wave mode of giant pulsations

On the standing wave mode of giant pulsations

Simultaneous observations of a pulsation event from the ground, with balloons and with a geostationary satellite on August 12, 1978

Interrelation between VLF and ULF emissions

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