Spatial distribution of the geomagnetic spectral composition for disturbed days.

Campbell, Wilbur H.

doi:10.5636/jgg.28.481

Cited by 13 publications

(5 citation statements)

References 10 publications

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“…It is now known that the radial diffusion coefficient for energetic particles in the earth's magnetosphere is not constant as a function of time, as was often assumed in the early days of radiation belt research [Lanzerotti et al, 1970[Lanzerotti et al, , 1978. Rather, third-invariant violation depends upon the level of geomagnetic activity, as would be expected from contemporary knowledge of geomagnetic 'noise' levels [e.g., Surkan and Lanzerotti, 1974;Campbell, 1976Campbell, , 1977. As such, the radial diffusion problem is more complicated than that envisioned a decade and a half ago.…”

Section: Introductionmentioning

confidence: 99%

Particle diffusion in the geomagnetosphere: Comparison of estimates from measurements of magnetic and electric field fluctuations

Lanzerotti¹,

Wolfe²

1980

J. Geophys. Res.

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We present a comparison of particle radial diffusion in the earth's magnetosphere that is determined from measurements of fluctuating magnetic and electric fields. We show, for a day when simultaneous satellite and ground-based magnetic field data and published electric field data are available, that estimates of the radial diffusion from these fluctuating fields are comparable. We also show that the fluctuating fields at high latitudes, in the auroral zone, produce radial diffusion coef•cients a factor of ten larger than would be expected by the extrapolation of subauroral latitude observations to higher latitudes.

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Section: Introductionmentioning

confidence: 99%

Particle diffusion in the geomagnetosphere: Comparison of estimates from measurements of magnetic and electric field fluctuations

Lanzerotti¹,

Wolfe²

1980

J. Geophys. Res.

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“…Differences in the temporal and spatial features of the spectra for three period samples are shown. On many days the high latitude activity was more evenly spread throughout the day than was found for the geomagnetically active days (CAMPBELL, 1976c). The two clear exceptions to this were on 10 November and 28 April.…”

Section: Spectral Amplitudesmentioning

confidence: 80%

“…Table 3 shows the linear relationship for which the data set included the 6 quiet days of Table 1 plus the 7 active day analyzed in the earlier paper (CAMPBELL, 1976c). The correlation coefficients are quite high at each period sampled.…”

Section: Spectral Amplitudesmentioning

confidence: 92%

“…A study of the shorter period spectral range was presented by WERTZ and CAMPBELL (1976). In the same period range as this paper the characteristics of the average day spectra (CAMPBELL 1976a) and the disturbance-time spectra (CAMPBELL, 1976c) have already been completed. Results from these last two studies will be mentioned again in this paper for comparison with quiet-time field characteristics.…”

Section: Introductionmentioning

confidence: 98%

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Spectral characteristics of field variations during geomagnetically quiet conditions.

Campbell

1977

J. geomagn. geoelec

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Using data from 15 observatories at a wide distribution of latitude locations in North and South America the spectra of geomagnetic field variations having periods from 5 min to 4 hr were examined for six days of 1965 when the Ap index values were 3 or less. At high latitudes, where the maximum amplitudes occurred more poleward on low Ap days than on high Ap days, the ratio of the short to long period amplitudes was higher than at other latitudes. For all spectral samples of the data, a minimum in activity was found near 30 geomagnetic latitude and a dayside enhancement was found at the equator. At all latitudes most amplitudes were larger during the local daytime hours and smallest at the predawn hours. East-west component amplitudes were about the same size as the north-south component amplitudes averaged over the day yet regular diurnal variations were found in the ratio of these two components. On the average there was a 10 to 20 percent reduction of the east-west field component in the region of the ionospheric equatorial and auroral electrojet currents. The vertical component of field was about 40 percent less than the horizontal field. This reduction seemed to be accounted for by an effective crustal conductivity of about 2X10-3mhos/ meter extending to an equivalent depth of about 300km. The general characteristics of the quiet-time spectra seemed to match the projection of the changes in active-day spectra to low Ap values. Empirical relationships between the spectral features and the Ap index are provided to allow some prediction of geomagnetic amplitude levels as a function of period, time, and location on magnetically quiet days.

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“…The nature of the spectral power of geoelectric fluctuations over large distances is of intrinsic scientific interest as well as of interest for more practical concerns related to the installation and maintenance of technological systems composed of long conductors grounded to the Earth. While power spectral studies of geomagnetic field fluctuations have been investigated on a 'global' scale, using spaced magnetometers, for more than two decades [see especially Campbell, 1976aCampbell, ,b, 1977Wertz and Campbell, 1976], geoelectric measurements have generally been confined to more local and regional studies, primarily associated with magnetotelluric studies of the Earth's conductivity structure.…”

Section: Introductionmentioning

confidence: 99%

Geoelectric power spectra over oceanic distances

Fujii

Lanzerotti

Utada

et al. 1995

Geophysical Research Letters

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We present initial results of simultaneous measurements of the geoelectric potential as measured across two long cable routes in the Pacific (Guam to Philippines and California to Hawaii) separated by ∼6h in local time and ∼30° in latitude. Over the frequency range ∼10−5 to 1.67 × 10−3Hz the power levels tend to be enhanced near local noon along the two routes, especially during geomagnetic quiet intervals. During the seven days analyzed, geoelectric power levels up to 104 (mV/km)²/km were measured on a geomagnetically disturbed day. The power levels at the longest periods, ∼17m to ∼150m, are generally found to be largest along the route at lower geomagnetic latitudes (Guam to Philippines) when comparisons are made at equivalent local times. In contrast, the power levels for periods in the hydromagnetic wave region (periods ≲5m) tend to be larger at all local times for the higher geomagnetic latitude route. The nightside geoelectric power levels along the higher latitude route tend to increase with increasing geomagnetic activity.

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Spatial distribution of the geomagnetic spectral composition for disturbed days.

Cited by 13 publications

References 10 publications

Particle diffusion in the geomagnetosphere: Comparison of estimates from measurements of magnetic and electric field fluctuations

Particle diffusion in the geomagnetosphere: Comparison of estimates from measurements of magnetic and electric field fluctuations

Spectral characteristics of field variations during geomagnetically quiet conditions.

Geoelectric power spectra over oceanic distances

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