Modulation of auroral electrons at large distances from the Earth

Bryant, D. A.; Courtier, G. M.; Johnstone, A. D.

doi:10.1016/0021-9169(69)90010-5

Cited by 28 publications

(11 citation statements)

References 10 publications

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“…Even when the patch does not move, the rotation of magnetic vectors could occur due to the temporal and spatial change in the Hall/Pedersen ratio throughout a pulsation. The relaxation time of ionization depends on altitude and, in addition, there is a velocity dispersion of precipitation electrons [Bryant et al, 1969[Bryant et al, , 1971] at rocket altitudes. These would cause different growth and decay of the two currents, the field-aligned pair current and the twin vortex current, and accordingly could cause a temporal rotation of the magnetic deflection pattern in Figure I This study can be summarized as follows.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Multiple correlation between auroral and magnetic pulsations: 2. Determination of electric currents and electric fields around a pulsating auroral patch

Oguti¹,

Hayashi²

1984

J. Geophys. Res.

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The multiple correlation method has been applied to the study of concurrent auroral and magnetic pulsations on the basis of videotapes of all‐sky television camera auroral records and induction magnetometer records. The results are (1) the ground magnetic pulsations below pulsating auroras are well represented by a regression model where the magnetic change is expressed as a linear combination of auroral luminosity fluctuations at various parts of the sky, (2) the magnetic variation observed at a single station can be broken down into the magnetic contributions from various auroral patches, and subsequently, (3) the magnetic deflections at various ground points below a pulsating auroral form can be estimated even when many pulsating patches appear at the same time. It is also shown that (4) the horizontal magnetic deflections deduced from observations by use of this technique are fully explained by the combination of ionospheric and field‐aligned electric currents which are theoretically expected to be induced in and near a local enhancement of conductivity under the existence of a uniform, ambient electric field. This study thus gives a definite proof that the ground magnetic pulsation which occurs concurrently with auroral pulsations in the auroral oval is the result of successive growth and decay processes of the localized electric currents in and in the vicinity of pulsating auroral forms, which are caused by a conductivity pulsation due to the pulsating precipitation of auroral electrons in conjunction with the convection electric field. The model calculation also predicts the distribution pattern and intensity of the fluctuating electric fields below pulsating auroral patches.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Multiple correlation between auroral and magnetic pulsations: 2. Determination of electric currents and electric fields around a pulsating auroral patch

Oguti¹,

Hayashi²

1984

J. Geophys. Res.

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“…(There are other types of events that may occasionally be termed 'pulsating aurorae,' especially on the nightside during active periods; it should be kept in mind that there may be several distinct phenomena, some of them associated with electric fields, etc.) The evidence from time dispersion measurements points to high altitudes--perhaps near the equatorial plane--as the location of the wave-particle interaction that precipitates the electrons [Bryant et al, 1969[Bryant et al, , 1971 weak diffusion or selective loss by narrowband interactions rather than strong diffusion. This conclusion should, however, be accepted with caution because the high-altitude observations have not been correlated with pulsating aurorae.…”

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confidence: 99%

Self‐modulated VLF wave‐electron interactions in the magnetosphere: A cause of auroral pulsations

Davidson¹

1979

J. Geophys. Res.

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A model is developed for self‐modulated pulsations in the outer trapped electron belts. The pulsations are a consequence of growth of VLF waves and removal of trapped electrons following an electron injection event. If too many electrons are removed by wave interactions, the system restores itself by building up the flux again to values exceeding the equilibrium flux, repeated through many cycles. Pulsations are shown to be possible for both broadband VLF wave generation and narrowband wave generation. The resulting electron precipitation pulses are consistent with observations of pulsating aurorae on the morningside following a substorm injection event. The conditions for pulsations are quite stringent and favor trapped particle fluxes near the stable trapping limit. Individual pulses may be in or near strong diffusion.

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“…This has been accomplished by a two-step process. The first step is based on rocket observations that higher energy pulsations arrive before lower energy pulsations (Bryant et al, 1967(Bryant et al, , 1969(Bryant et al, , 1971(Bryant et al, , 1975Lepine et al, 1980;Smith et al, 1980). The second step is to assume that the electrons which cause the pulsations are simultaneously produced in the same region and extrapolating backward along the magnetic field line, the location of the modulation region is generally found to be in the equatorial region (Bryant et al, 1975;Smith et al, 1980).…”

Section: Introductionmentioning

confidence: 99%

Parallel electric fields inferred during a pulsating aurora

et al. 2006

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Abstract.A sounding rocket, equipped to study pulsating aurora launched from Poker Flat, Alaska on 13 March 1997 at 10:20:31 UT, measured electron precipitation over the range ∼10 eV to 500 keV covering pitch-angles from 0 to 180 • . Data show electrons with energies <1 keV are mostly secondaries produced below the rocket altitude by the higher energy precipitated electrons. We observed nearly equal fluxes of up and down going electrons for energies <1 keV at altitudes from 265 to 380 km. Electron transport simulation results indicate the secondaries produced by the more energetic electrons will have two times higher flux in the upward direction as compared to the downward direction. Our observations of nearly equal fluxes of up and downgoing electrons over a large range of altitudes is consistent with the presence of an electric potential above the rocket that reflects the upgoing electrons back toward the rocket where they are detected as downward going electrons. The strength of the potential is estimated to be 1.5±0.5 kV and its location is no greater than 5000 km above the rocket. Finally, the inferred potential drop exists independently of the presence of pulsations.

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Modulation of auroral electrons at large distances from the Earth

Cited by 28 publications

References 10 publications

Multiple correlation between auroral and magnetic pulsations: 2. Determination of electric currents and electric fields around a pulsating auroral patch

Multiple correlation between auroral and magnetic pulsations: 2. Determination of electric currents and electric fields around a pulsating auroral patch

Self‐modulated VLF wave‐electron interactions in the magnetosphere: A cause of auroral pulsations

Parallel electric fields inferred during a pulsating aurora

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