The auroral oval and the boundary of closed field lines of geomagnetic field

Feldstein, Y. I.; Starkov, G. V.

doi:10.1016/0032-0633(70)90127-3

Cited by 77 publications

(30 citation statements)

References 12 publications

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“…The obtained latitude around noon is consistent with earlier reports (e.g. Feldstein and Starkov, 1970). In the dawn, noon, and dusk sectors the boundary moves to lower latitudes with increasing magnetic activity, while the boundary around midnight seems to be stationary on average at a value of about 72 • Mlat, showing little dependence on magnetic activity.…”

Section: Magnetic Latitude and Mlt Distribution Of The Auroral Oval Isupporting

confidence: 92%

“…There are also some models for predicting the location of the auroral oval (e.g. Feldstein and Starkov, 1970;Holzworth and Meng, 1975) and the global distribution of the electrons and ions streaming into the ionosphere (Hardy et al, 1985). Based on the energetic spectra measured by the special sensor for precipitating particles on the Defense Meteorological Satellite Program (DMSP), the auroral boundary index (ABI) model is provided to estimate the equatorward boundary of precipitating auroral electrons (Hardy et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1

et al. 2014

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Abstract. In this paper we present the first statistical study on auroral oval boundaries derived from small-and mediumscale field-aligned currents (FACs, < 150 km). The dynamics of both the equatorward and poleward boundaries is deduced from 10 years of CHAMP (CHAllenging Minisatellite Payload) magnetic field data (August 2000-August 2010). The approach for detecting the boundaries from FACs works well under dark conditions. For a given activity level the boundaries form well-defined ellipses around the magnetic pole. The latitudes of the equatorward and poleward boundaries both depend, but in different ways, on magnetic activity. With increasing magnetic activity the equatorward boundary expands everywhere, while the poleward boundary shows on average no dependence on activity around midnight, which seems to be stationary at a value of about 72 • Mlat. Functional relations between the latitudes of the boundaries and different magnetic activity indices have been tested. Best results for a linear dependence are derived for both boundaries with the dayside merging electric field. The other indices, like the auroral electrojet (AE) and disturbance storm time (Dst) index, also provide good linear relations but with some caveats. Toward high activity a saturation of equatorwards expansion seems to set in. The locations of the auroral boundaries are practically independent of the level of the solar EUV flux and show no dependence on season.

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Section: Magnetic Latitude and Mlt Distribution Of The Auroral Oval Isupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1

et al. 2014

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show abstract

“…The resulting figure was made up from a statistical study showing the poleward and equatorward auroral boundaries of the 75% occurrence probability (Feldstein 1963(Feldstein , 1973Feldstein & Starkov 1970). The relationship between the morphology of the auroral oval and the level of geomagnetic activity allows us to develop models of the location of the aurora, independent of the vagaries of auroral observations (Holzworth & Meng 1975;Starkov 1994a).…”

Section: Introductionmentioning

confidence: 99%

Two methods to forecast auroral displays

Sigernes¹,

Dyrland²,

Brekke

et al. 2011

J. Space Weather Space Clim.

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This work compares the methods by Starkov (1994a) and Zhang & Paxton (2008), that calculate the size and location of the auroral ovals as a function of planetary Kp index. The ovals are mapped in position and time onto a solar illuminated surface model of the Earth. It displays both the night-and dayside together with the location of the twilight zone as Earth rotates under the ovals. The graphical display serves as a tool to forecast auroral activity based on the predicted value of the Kp index. The forecast is installed as a service at http://kho.unis.no/. The Zhang & Paxton (2008) ovals are wider in latitude than the Starkov (1994a) ovals. The nightside model ovals coincide fairly well in shape for low to normal auroral conditions. The equatorward border of the diffuse aurora is well defined by both methods on the nightside for Kp 7. The dayside needs further studies in order to conclude.

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“…I. FELDSTEIN Measurements of trapped particles first revealed that the outer edge of the Van Allen belt (the Stable Trapping Boundary, STB) has an asymmetric form similar to the oval, and is nearly colocated with it (O 'Brien, 1963;Frank et al, 1964, Akasofu, 1968. Feldstein and Starkov (1970) have shown that this colocation extends to all levels of geomagnetic activity and the average location of the Stable Trapping Boundary (A5) within statistical errors coincides with the equatorial boundary of the statistical auroral oval. Auroral oval location was proposed by Akasofu (1968) as a natural magnetospheric coordinate system.…”

Section: Introduction Some History and Limitationsmentioning

confidence: 99%

Mapping of the Precipitation Regions to the Plasma Sheet

Galperin

Feldstein²

1996

J. geomagn. geoelec

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The progress in the mapping of the auroral regions in the Earth's polar ionosphere to outer magnetosphere reflects our growing understanding of the gross magnetospheric structure. Several "natural tracers" were identified and used by us for the mapping scheme advocated for more than a decade. A "natural tracer" is a plasma boundary identifiable at different altitudes which, from physical reasons, is aligned along the magnetic flux tube (accounting for cross-field convection). The boundaries' locations describe the current state of the magnetosphere. The following tracers to the tail were used in our studies: the lowlatitude Soft Electron precipitation Boundary; the large-scale Convection Boundary, or an Alfven Layer; the Plasmapause; the Stable Trapping Boundary for high energy electrons; the precipitating hot ion Isotropy Boundary; the two types of Velocity-Dispersed Ion Structures: VDIS-1 (adjacent to an electron inverted-V structure within the oval), and VDIS-2 (just poleward from the oval). A new "Wall Region" concept related to non-adiabatic (non-MHD) ion dynamics allows to add its effects in the list of "natural tracers". Another newly discovered structure in the tail is the Low Energy Layer of counter-streaming low-energy (<100 eV) ions and electrons at the outer edge of the Boundary Plasma Sheet. Its physical origin in the far tail, and respective source location, are debatable. Physical limits to the MHD-mapping approach are placed by plasma and field fluctuations and turbulence, by finite Larmor radius effects including non-adiabatic particle dynamics, by finite Alfven propagation times in the magnetosphere, and by various medium-and large-scale disturbances-"auroral activation".

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The auroral oval and the boundary of closed field lines of geomagnetic field

Cited by 77 publications

References 12 publications

Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1

Determining the boundaries of the auroral oval from CHAMP field-aligned current signatures – Part 1

Two methods to forecast auroral displays

Mapping of the Precipitation Regions to the Plasma Sheet

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