Localized aurora beyond the auroral oval

Frey, H. U.

doi:10.1029/2005rg000174

Cited by 113 publications

(133 citation statements)

References 210 publications

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“…The speed of poleward progression was ∼300 m s −1 . The equatorward "end" of the arcs was seen to be "buried' into the auroral oval luminosity band, similar to what has been reported for the theta aurora (Zhu et al, 1997;Frey, 2007;Newell et al, 2009). There were some dynamical changes in the arcs' configuration and in the plasma flows at the "juncture" of the arcs and the oval that were, however, not focused on in this study as our goal was to show signatures of the arcs in their central parts where the features are easier to identify.…”

Section: Discussionsupporting

confidence: 82%

Signatures of moving polar cap arcs in the F-region PolarDARN echoes

et al. 2012

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Abstract. Joint observations of the all-sky camera at Resolute Bay (Nunavut, Canada) and the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Rankin Inlet and Inuvik (Canada) are considered to establish radar signatures of poleward moving polar cap arcs "detaching" from the auroral oval. Common features of the events considered are enhanced power or echo occurrence in the wake of the arcs and enhanced spectral width of these echoes. When the arcs were oriented along some of the radar beams, velocity reversals at the arc location were observed with the directions of the arc-associated flows corresponding to a converging electric field. For the event of 9 December 2007, two arcs were poleward progressing almost along the central beams of the Inuvik radar at the speed close to the E × B drift of the bulk of the F-region plasma as inferred from HF Doppler velocities and from independent measurements by the Resolute Bay ionosonde. In global-scale convection maps inferred from all Super Dual Auroral Radar Network (SuperDARN) radar measurements, the polar cap arcs were often seen close to the reversal line of additional mesoscale convection cells located poleward of the normal cells related to the auroral oval.

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Section: Discussionsupporting

confidence: 82%

Signatures of moving polar cap arcs in the F-region PolarDARN echoes

et al. 2012

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“…The technique as outlined requires that each MLT sector be well modelled either as a continuous single or double auroral oval and so will not provide an accurate representation of more complex auroral configurations (see Frey, 2007, for a review of localised auroral features outside the main oval). No explicit distinction is made between a double oval and other auroral features that may appear poleward of the main oval, such as high-latitude sun-aligned arcs.…”

Section: Technique Limitationsmentioning

confidence: 99%

Estimating the location of the open-closed magnetic field line boundary from auroral images

et al. 2010

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Abstract. The open-closed magnetic field line boundary (OCB) delimits the region of open magnetic flux forming the polar cap in the Earth's ionosphere. We present a reliable, automated method for determining the location of the poleward auroral luminosity boundary (PALB) from far ultraviolet (FUV) images of the aurora, which we use as a proxy for the OCB. This technique models latitudinal profiles of auroral luminosity as both a single and double Gaussian function with a quadratic background to produce estimates of the PALB without prior knowledge of the level of auroral activity or of the presence of bifurcation in the auroral oval. We have applied this technique to FUV images recorded by the IMAGE satellite from May 2000 until August 2002 to produce a database of over a million PALB location estimates, which is freely available to download. From this database, we assess and illustrate the accuracy and reliability of this technique during varying geomagnetic conditions. We find that up to 35% of our PALB estimates are made from double Gaussian fits to latitudinal intensity profiles, in preference to single Gaussian fits, in nightside magnetic local time (MLT) sectors. The accuracy of our PALBs as a proxy for the location of the OCB is evaluated by comparison with particle precipitation boundary (PPB) proxies from the DMSP satellites. We demonstrate the value of this technique in estimating the total rate of magnetic reconnection from the time variation of the polar cap area calculated from our OCB estimates.

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“…The precipitating particles excite atmospheric atoms and molecules and thus cause luminosity both in visible and ultraviolet (UV) wavelengths. Viewed from space with a global imager, the aurora appears as diffuse, continuous, luminous bands that surround both geomagnetic poles at ionospheric altitudes (Frey, 2007). Since the concept of the auroral oval was put forward by Feldstein (1963) and Khorosheva (1967), there have been a large number of observations and models related to this phenomenon (Eather, 1973;Kauristie, 1995;Elphinstone et al, 1996;Yahnin et al, 2006).…”

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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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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Localized aurora beyond the auroral oval

Cited by 113 publications

References 210 publications

Signatures of moving polar cap arcs in the F-region PolarDARN echoes

Signatures of moving polar cap arcs in the F-region PolarDARN echoes

Estimating the location of the open-closed magnetic field line boundary from auroral images

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

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