Distributions and characteristics of high-latitude field-aligned electron precipitation

Berko, F. W.

doi:10.1029/ja078i010p01615

Cited by 36 publications

(34 citation statements)

References 29 publications

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“…The amplitude of the peaks has a minimum at 02-04 MLT which might indicate that the midnight peaks have a different source than the day peaks. It may also be pointed out that anisotropies at 2.3 keV electrons reported by Berko (1972) have a maximum occurrence at midnight and at 70-72° in invariant latitude and decrease towards dawn with very few cases found on the dayside, while anisotropies at 1.3 keV reported by Holmgren and Aparicio (1972) show a second maximum in the day. This indicates also that there are two different kinds of particle populations at these low energies in the latitude range where the 0.7 keV peaks are observed.…”

Section: Discussionmentioning

confidence: 85%

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Gustafsson¹

1973

J. Geophys. Res.

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Data from particle detectors on board the satellite Ogo 4 were used to study the precipitation of electrons in the energy range 0.7–24 kev. The latitude dependence of these particles in the local time region from midnight to dawn has been investigated in detail. The analysis shows that the precipitation of particles of energies 2.3–24 kev is centered at an invariant latitude of about 68° at midnight with a clear shift in latitude with increasing local time, and that this shift is more pronounced for lower energies. The highest fluxes of particles in this energy interval are measured at midnight, and they decrease rapidly with local time. In the dawn region, the location of the maximum precipitation for different energies varies about 1 ° of latitude for each unit of Kp, but the relative distribution remains almost unchanged. The fact that different energies have their maximums at different latitudes implies that the flux spectrum of precipitated particles, when measured at a certain latitude, has a peak at an energy corresponding to the energy of maximum precipitation at the latitude. The data in the energy range 2.3–24 kev support a theory in which particles are injected in the midnight region from the tail, gain energy owing to a betatron process, and then drift eastward in a combined electric and magnetic field. The main part of the electrons at 0.7 kev show a different behavior than do those at higher energies. They seem to undergo an acceleration process that is rather local, sometimes giving field‐aligned fluxes that may be superimposed on the background precipitation. The structural precipitation of 0.7‐kev electrons has been found to coincide on a statistical basis with the region of structural aurora indicating a relationship between the two phenomena.

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Section: Discussionmentioning

confidence: 85%

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Gustafsson¹

1973

J. Geophys. Res.

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“…According to the statistics of the S3-3 data in the auroral oval, the field-aligned electrons were considered to be stable in a circumpolar zone (Collin et al, 1982). Berko (1973) studied the field-aligned electron precipitation that was most likely to occur when particle fluxes were high. He also noticed that the field-aligned precipitation generally was a short-time duration phenomenon, rarely appearing continuously for more than 5 to 10 s according to the data from the OGO 4 satellite at an altitude of 412-908 km.…”

Section: Introductionmentioning

confidence: 99%

“…By analyzing the OGO 4 satellite data at altitudes of 412-908 km, Berko (1973) pointed out that the FAEs were distributed over the entire auroral oval with a maximum occurrence at about ILAT (invariant latitude) 70°-72.5°in the range of magnetic local time (MLT) 2200-0100(+1). Using S3-3 data obtained at low altitude (3,000-8,000 km) in the northern polar region, Collin et al (1982) have shown that the FAEs were limited to an ILAT range within 63-81°, and the MLT distribution was double peaked in the morning and evening at MLT 0700 and 2200, respectively, and only in the northern polar region.…”

Section: Introductionmentioning

confidence: 99%

Distribution of Field‐Aligned Electron Events in the High‐Altitude Polar Region: Cluster Observations

et al. 2017

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Field‐aligned electrons (FAEs) are important for the energy transport in the solar wind‐magnetosphere‐ionosphere coupling. However, the distribution of FAEs and the concerning physical mechanism in different altitudes of the polar region are still unclear. In this paper, data from the Cluster spacecraft were used to study the characteristics of FAEs in high‐altitude polar region. We selected FAE events with a flux higher than 3 × 108(cm2 s)−1 for our analysis. Their distribution was double peaked around the auroral oval. The main peak occurred around the cusp region (magnetic local time (MLT) 0700–1500) which leaned to the dawnside. The other peak appeared in the evening sector with MLT 2100–2300 just before midnight. The durations of the FAE events covered a wide range from 4 to 475 s, with most of the FAE events lasting less than 40 s. The possible physical mechanisms are discussed, namely, that the downward FAEs may consist of decelerated solar wind and reflected up flowing ionospheric electrons in the potential drops, whereas the upward ones may be mirrored solar wind electrons and accelerated ionospheric up flowing electrons.

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“…The spatial distribution and spectral characteristics of 2.3 keV field-aligned electrons have been presented in a statistical study by Berko (1973).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous particle and field observations of field-aligned currents

Berko¹,

Hoffman²,

Burton³

et al. 1975

J. Geophys. Res.

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Simultaneous measurements of low‐energy precipitating electrons and magnetic fluctuations from the low‐altitude polar‐orbiting satellite Ogo 4 have been compared. Analysis of the two sets of experimental data for isolated events led to the classification of high‐latitude field‐aligned currents as purely temporal or purely spatial variations. Magnetic field disturbances calculated by using these simple current models and the measured particle fluxes were in good agreement with measured field values. Although fluxes of electrons of greater than 1 keV were detected primarily on the night side, magnetometer disturbances indicative of field‐aligned currents were seen at all local times, in both the visual auroral regions and the day side polar cusp. Thus electrons with energies of less than ∼1 keV are the prime charge carriers in high‐latitude day side field‐aligned currents. The satellite measurements are in good agreement with previously measured field‐aligned current values and with values predicted from several models involving magnetospheric field‐aligned currents.

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Distributions and characteristics of high-latitude field-aligned electron precipitation

Cited by 36 publications

References 29 publications

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Distribution of Field‐Aligned Electron Events in the High‐Altitude Polar Region: Cluster Observations

Simultaneous particle and field observations of field-aligned currents

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