Tail field effects on drift mirror instability

Lin, C. S.; Cheng, C. Z.

doi:10.1029/ja089ia12p10771

Cited by 8 publications

(4 citation statements)

References 26 publications

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“…Thus internal excitation of the compressional waves has been considered the likely source. Spatial gradient and anisotropy of plasma pressure in the ring current region, for example, can provide free energy for exciting ULF waves, and instabilities related to such free energy have been discussed theoretically [Hasegawa, 1969;Southwood, 1973Southwood, , 1976Walker et al, 1982;Patel et al, 1983;Lin and Cheng, 1984].…”

Section: Southwoodmentioning

confidence: 99%

Antisymmetric standing wave structure associated with the compressional Pc 5 pulsation of November 14, 1979

Takahashi¹,

Higbie²

1986

J. Geophys. Res.

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Model calculations are performed to explain ion and electron flux pulsations observed at geostationary orbit in association with the compressional Pc 5 magnetic pulsation of November 14, 1979. The amplitude of the flux perturbation is calculated based on the observed value of the wave frequency, the azimuthal wave number, and the average distribution f(W, α) of the particles, for assumed forms of a standing wave structure along the ambient magnetic field. A theory developed by Southwood and Kivelson is followed to calculate the changes in energy and the location of the guiding center, which are experienced by particles in a given wave, and the consequential modulation of particle fluxes. It is found that if the compressional magnetic field component b∥ of the wave has a symmetric structure about the equator, net acceleration of the particles contributes significantly to the total amplitude of flux pulsations; whereas if b∥ has an antisymmetric structure, the total energy is conserved with the exchange of perpendicular and parallel energy leading to the modulation of the pitch angle distribution as the dominant cause of the flux pulsation. For the latter case, local magnetic field compression and the pitch angle dependence of the average particle distribution determine the amplitude of the flux pulsation. We find that antisymmetric models of b∥ reproduce the observations better than symmetric models. This result implies that there exists a class of compressional Pc 5 waves that do not have a fundamental standing wave structure.

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Section: Southwoodmentioning

confidence: 99%

Antisymmetric standing wave structure associated with the compressional Pc 5 pulsation of November 14, 1979

Takahashi¹,

Higbie²

1986

J. Geophys. Res.

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“…For the first time, these satellite observations can provide an important test to the theories of the storm time Pc 5 waves. Previous theories of the storm time Pc 5 waves have been presented in terms of drift mirror instabilities [Hasegawa, 1969;Walker et al, 1982;Lin and Cheng, 1984], drift compressional instabilities [Hasegawa, 1971;Kg et al f 1984], bounce magnetic drift resonance excitation of ULF waves [Southwood, 1976], and boxmodel of externally driven Alfven waves [Southwood and Kivelson, 1986]; however, the field-aligned mode structures have not been studied. In this paper, we will present an eigenmode analysis of long wavelength (kp < 1), low frequency (w < aiu) compressional waves in a dipole magnetic field, where p is the hot particle gyroradius and w b is the hot particle bounce frequency.…”

Section: Introductionmentioning

confidence: 99%

Eigenmode analysis of compressional waves in the magnetosphere

Cheng¹,

Lin²

1987

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A field-aligned eigenmode analysis of compressional AlfvSn instabilities has been performed for a two component anisotropic plasma in a dipole magnetic field. The eigenmode equations are derived from the gyrokinetic equations in the long wavelength (kp < 1) and low frequency (u < n» h) limits, where p is the hot particle gyroradius and u b is the hot particle bounce frequency. Two types of compressional instabilities are identified. One is the drift mirror mode which has an odd parity compressional magnetic component with respect to the magnetic equator. The other is the drift compressional mode with an even parity compressional magnetic component. For typical storm time plasma parameters near geosynchronous orbit, the drift mirror mode is most unstable and the drift compressional mode is stable. The storm time compressional Pc 5 waves, observed by multiple satellites during November 14-15, 1979 [Takahashi et al., 1987], can be explained by the drift mirror instability.

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“…Hasegawa's drift mirror instability, as well as its modified versions [Lin and Parks, 1978;Walker et al, 1982], used a plane magnetic field geometry; therefore it was not possible for the theory to discuss the effect of particle bounce and the amplitude structure along the dipole field. Only recently has a realistic field geometry been taken into account in the calculation of the growth rate and the field-aligned structure of unstable ULF waves [Lin and Cheng, 1984;Cheng and Lin, 1987;Cheng and Hasegawa, 1987].…”

mentioning

confidence: 99%

An eastward propagating compressional Pc 5 wave observed by AMPTE/CCE in the postmidnight sector

Takahashi¹,

López²,

McEntire³

et al. 1987

J. Geophys. Res.

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Data from three instruments, the magnetometer, the charge‐energy‐mass spectrometer, and the medium‐energy particle, analyzer onboard the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (CCE) spacecraft have been used to study a compressional Pc 5 wave observed at 1925–2200 UT on day 202 (July 21) of 1986 at a radial distance of ≃8 RE in the postmidnight sector near the beginning of minor geomagnetic activity. The wave exhibited harmonically related transverse and compressional magnetic oscillations, modulation of the flux of medium energy protons (E ≳ 10 keV), and a large azimuthal wave number (m ∼ 65). These properties are similar to those of compressional Pc5 waves observed previously at geostationary orbit. The unique observations associated with the CCE event are the occurrence in the postmidnight sector, the eastward (or sunward) propagation with respect to the spacecraft, and the left‐handed polarization of the perturbed magnetic field. These are opposite to previous geostationary observations. We propose that the unique propagation and polarization are caused by a dawn‐to‐dusk dc electric field which convects the plasma sunward. The wave, probably propagating westward in the plasma rest frame, appears to propagate eastward to the observer because the electric field drift velocity is larger than the wave phase velocity.

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Tail field effects on drift mirror instability

Cited by 8 publications

References 26 publications

Antisymmetric standing wave structure associated with the compressional Pc 5 pulsation of November 14, 1979

Antisymmetric standing wave structure associated with the compressional Pc 5 pulsation of November 14, 1979

Eigenmode analysis of compressional waves in the magnetosphere

An eastward propagating compressional Pc 5 wave observed by AMPTE/CCE in the postmidnight sector

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