Measurements of the Poynting vector of standing hydromagnetic waves at geosynchronous orbit

Cummings, W. D.; Deforest, S. E.; McPherron, R. L.

doi:10.1029/ja083ia02p00697

Cited by 60 publications

(34 citation statements)

References 29 publications

(4 reference statements)

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“…A succession of papers using data from a variety of spacecraft has examined variations in particle flux in magnetospheric pulsation events [Brown et Kokubun et al, 1977;Cummings et al, 1978]. The standing structure also means that the wave field should exhibit some symmetry about the field line equator.…”

Section: Introductionmentioning

confidence: 99%

Charged particle behavior in low‐frequency geomagnetic pulsations: 3. Spin phase dependence

Kivelson¹,

Southwood²

1983

J. Geophys. Res.

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The behavior of charged particles in low-frequency geomagnetic pulsations is examined with particular emphasis on what a spacecraft-borne detector would observe. We concentrate on the effects of purely transverse electromagnetic signals. The time scale of a particle's motion relative to the wave period is shown to determine the nature of its response. For low-energy particles, the acceleration in the last gyroperiod before detection is what matters. At higher energies, what has occurred over recent bounce and drift motions becomes increasingly important and convection of gradients by the wave E x B drift must be considered. Distinguishing features such as phase differences between signals in back-to-back detectors or between channels of different energy are catalogued. In particular, we assess the detectability of resonance effects in the light of detector characteristics and finite signal bandwidth. Recent observations are used to illustrate the ideas developed.

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Section: Introductionmentioning

confidence: 99%

Charged particle behavior in low‐frequency geomagnetic pulsations: 3. Spin phase dependence

Kivelson¹,

Southwood²

1983

J. Geophys. Res.

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“…This technique has been used for shear Alfv6n waves in the Pc3, 4, and 5 bands [Cummings et al, 1978;Singer and Kivelson, 1979;Cahill et al, 1986] and for fast mode waves in the Pc3 band [Takahashi et al, 1994]. To see how it works, consider Faraday's law…”

Section: Introductionmentioning

confidence: 99%

CRRES satellite observations associated with low‐latitude Pi2 pulsations

Takahashi¹,

Hughes²,

Anderson³

et al. 1999

J. Geophys. Res.

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Abstract. We studied the electric and magnetic field variations and their relation to the ambient plasma density observed from the Combined Release and Radiation Effects Satellite (CRRES) during two Pi2 events observed on the ground at the low-latitude (L = 1.2) station Kakioka. At the time of the Pi2s, CRRES was moving outward at L -5, magnetic local time (MLT) of-2200, and magnetic latitude of-4 ø. The satellite was in an apparently detached dense plasmaspheric plasma for the first Pi2 but in a low-density region for the second Pi2. The first Pi2 had a period of 120 s at Kakioka (MLT-2000), and the satellite observed a nearly identical oscillation in the (approximately) azimuthal component of the electric field and in the radial and compressional components of the magnetic field. At CRRES the compressional magnetic field and the azimuthal electric field oscillated nearly in quadrature in the decaying phase of the pulsation, which suggests a radially trapped fast mode wave. However, comparison of this observation with numerical models of the plasmaspheric cavity mode is difficult because the plasma density did not have a simple plasmapause structure. The second Pi2 observed at Kakioka exhibited a period of 180 s and was similar to the azimuthal electric field oscillation seen at CRRES but quite different from the compressional magnetic perturbation at the satellite. For this event it is not clear whether the electric field oscillation represents a fast mode wave that was direc0y related to the ground Pi2 or a local shear Alfv6n wave that was not directly related to the Pi2. If the first interpretation is the case, the midlatitude Pi2 is not necessarily confined within the plasmasphere by fast mode trapping or cavity resonance. These examples indicate that electric field oscillations measured by equatorial satellites are a sensitive and possibly better indicator of the onset of substorms and that if the plasma density measurements are also available, the electric field data can be useful for identifying the wave mode of Pi2 pulsations.

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“…During the body of the Pi2 event the field components in question are thus in quadrature. phase with δ(E ν , b φ )∼90 • (Cummings et al, 1978). The situation is reversed for a satellite located just below the equatorial plane.…”

Section: Discussionmentioning

confidence: 86%

Evidence of standing waves during a Pi2 pulsation event observed on Cluster

et al. 2006

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Abstract.Observations of Pi2 pulsations at middle and low latitudes have been explained in terms of cavity mode resonances, whereas transients associated with field-aligned currents appear to be responsible for the high latitude Pi2 signature.Data from Cluster are used to study a Pi2 event observed at 18:09 UTC on 21 January 2003, when three of the satellites were within the plasmasphere (L=4.7, 4.5 and 4.6) while the fourth was on the plasmapause or in the plasmatrough (L=6.6). Simultaneous pulsations at ground observatories and the injection of particles at geosynchronous orbit corroborate the occurrence of a substorm.Evidence of a cavity mode resonance is established by considering the phase relationship between the orthogonal electric and magnetic field components associated with radial and field-aligned standing waves. The relative phase between satellites located on either side of the geomagnetic equator indicates that the field-aligned oscillation is an odd harmonic. Finite azimuthal Poynting flux suggests that the cavity is effectively open ended and the azimuthal wave number is estimated as m∼13.5.

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Measurements of the Poynting vector of standing hydromagnetic waves at geosynchronous orbit

Cited by 60 publications

References 29 publications

Charged particle behavior in low‐frequency geomagnetic pulsations: 3. Spin phase dependence

Charged particle behavior in low‐frequency geomagnetic pulsations: 3. Spin phase dependence

CRRES satellite observations associated with low‐latitude Pi2 pulsations

Evidence of standing waves during a Pi2 pulsation event observed on Cluster

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