Relationships of the characteristics of magnetohydrodynamic waves to plasma density gradients near L = 4

Lanzerotti, L. J.; Maclennan, C. G.; Fukunishi, H.

doi:10.1016/0021-9169(76)90039-8

Cited by 16 publications

(7 citation statements)

References 34 publications

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“…Satellite-borne probes [e.g., Tulunay and Sayers, 1971] and topside sounders [Chan and Colin, 1969;Rycroft and Thomas, 1970] have been the main data-gathering techniques for determining the trough's structure and behavior. These have been augmented at times by ground-based radio techniques [Liszka, 1965;Evans and Holt, 1973;Bates et al, 1973; G. N. Taylor, 1973;Mend#lo and Klobuchar, 1975] and magnetometer networks monitoring MHD wave polarization characteristics [Lanzerotti and Fukunishi, 1975;Lanzerotti et al, 1976]. These methods offer, in effect, different views of the F region trough with varying amounts of latitudinal resolution.…”

Section: Introductionmentioning

confidence: 99%

The baselevel ionospheric trough

Mendillo¹,

Chacko²

1977

J. Geophys. Res.

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Isis 2 electron density profiles of the topside F region obtained during December 1971 have led to a detailed examination of the ionosphere's 'main trough' region under an optimum set of geophysical conditions. A total of 30 individual satellite passes during a 21-day period were used to determine the trough's characteristic features under the conditions of midwinter in the northern hemisphere, midnight local time, and very low magnetic activity. The morphological description obtained from this rigidly consistent data base is termed the 'baselevel trough.' The latitudinal profile of the trough at hmax over the 40o-80 ø corrected geomagnetic latitude range shows that while the equatorward edge and the trough minimum are wide features (7 ø and 10 ø, respectively), the poleward wall is sharp (• 1• ø). The equatorward edge and the trough minimum tend to lose their distinct identities toward higher altitudes, while the magnitude of the poleward wall enhancement remains nearly constant at 2.15 from 450 to 950 km. The trough's poleward wall is found 1ø-2 ø lower in latitude than the statistical position of the equatorward edge of the diffuse aurora. Ratios of topside densities to the peak density reveal that the shape of the Ne(h) profiles is constant from mid-latitudes to the trough minimum. Within the minimum a relatively rapid change in topside shape occurs which marks the light ion depletion region characterized by high H+/O + transition heights. The northern terminus of the transition height enhancement agrees with the statistical position of the magnetospheric plasmapause. Estimates of plasma temperature (Te + Tt) show only modest enhancements within the trough minimum.

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Section: Introductionmentioning

confidence: 99%

The baselevel ionospheric trough

Mendillo¹,

Chacko²

1977

J. Geophys. Res.

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“…Variations in the precipitating electrons were also observed. The magnetic field data were acquired at the four Bell Laboratories stations in New Hampshire and Quebec as well as in the conjugate area at Siple Station (Sl), Antarctica [Lanzerotti et al, 1976]. The data were obtained from three-axis fluxgate magnetometers whose analog outputs were digitized at two second intervals and recorded in computer compatible format on magnetic tapes [Lanzerotti et al, 1972].…”

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confidence: 99%

On the relationship of ∼3 mHz (Pc5) electric, magnetic, and particle variations

Maclennan¹,

Lanzerotti²,

Hasegawa³

et al. 1978

Geophysical Research Letters

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The first evidence is presented of associated magnetic field, electric field, and electron precipitation fluctuations from ground‐based and balloon‐based measurements. The magnetic field fluctuations are produced by magnetohydrodynamic waves of approximately 5 min period in the earth ’s magnetosphere. The electric, magnetic, and particle variations are observed to be in close phase relationship when the measurements are made near the resonance region of the magnetospheric waves. When the resonance region is not close to the location of the electric field observations no clear wave‐associated electric field or particle variations are observed. The observed wave frequency is ∼3 times lower than the fundamental Alfvén resonance frequency. This may arise from a Doppler shift of the resonant frequency by a diamagnetic plasma drift. The height‐integrated ionospheric Pedersen conductivity deduced from the simultaneous electric and magnetic field variations corresponds to approximately 30 mho.

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“…Examinations of the magnetic field data from the four Bell Laboratories stations in the northern hemisphere area conjugate to Siple (see LANZEROTTI et al (1976) for station locations) also revealed no distinct associations. This is in contrast to the events in the previous study by LANZEROTTI et al (1978).…”

Section: Observationsmentioning

confidence: 96%

Impulsive, quasi-periodic variations in ionospheric absorption of cosmic radio noise.

Rosenberg

Lanzerotti

Maclennan

et al. 1979

J. geomagn. geoelec

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Cosmic radio noise data, acquired with a fast-response 30 MHz riometer at Siple Station, Antarctica (L4), show evidence of weak impulsive quasiperiodic variations in ionospheric absorption. Significant amplitude variations approaching 0.02 dB, approximately the statistical noise limit of the measurement, have been measured. An event typically will consist of 3 to 5 cycles of oscillation (N60 to 90sec period) and can occur during locally disturbed or quiet geomagnetic conditions. Usually the oscillations are not related closely to magnetic field fluctuations as measured on the ground at Siple or in the conjugate area. Conjugate bremsstrahlung X-ray data, available for one event, suggest that these absorption variations are caused by the impact on the ionosphere of a modulated flux of energetic electrons from the magnetosphere. Limited statistics on the location of the plasmapause suggest that these events occur close to, but on either side of, the boundary of the plasmasphere. These absorption oscillations may be another manifestation of the process that produces short-term intensity and phase variations in fixedfrequency sub-ionospheric LF and VLF wave propagation. Further studies of this unique modulated precipitation/absorption phenomenon and its relationship to hydromagnetic wave disturbances in the magnetosphere will be conducted with a set of riometer and magnetometer stations appropriately sited in a latitude array.

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Relationships of the characteristics of magnetohydrodynamic waves to plasma density gradients near L = 4

Cited by 16 publications

References 34 publications

The baselevel ionospheric trough

The baselevel ionospheric trough

On the relationship of ∼3 mHz (Pc5) electric, magnetic, and particle variations

Impulsive, quasi-periodic variations in ionospheric absorption of cosmic radio noise.

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