Transpolar aurora: time evolution, associated convection patterns, and a possible cause

Blomberg, Lars G.; Cumnock, J. A.; Alexeev, I. I.; Bobrovnikov, Sergey; Калегаев, В. В.

doi:10.5194/angeo-23-1917-2005

Cited by 12 publications

(7 citation statements)

References 59 publications

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“…It is very likely that processes of merging between the IMF and Earth's magnetic field were involved in their formation (e.g. Blomberg et al, 2005). Sojka et al (1994) proposed the coupled magnetosphereionosphere model that considers a shear Alfvén wave interacting with the ionosphere.…”

Section: Discussionmentioning

confidence: 99%

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: Discussionmentioning

confidence: 99%

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

et al. 2012

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“…The emissions are thus likely associated with the currents set up by "lobe reconnection" between interplanetary and open tail lobe field lines, equivalent to the "NBZ currents" that occur at Earth (see Fig. 6 of Blomberg et al, 2005 and Fig. 8 of Belenkaya et al, 2006b), as also suggested by Meredith et al (2014).…”

Section: Auroral Source Locationsmentioning

confidence: 99%

Magnetospheric magnetic field modelling for the 2011 and 2012 HST Saturn aurora campaigns – implications for auroral source regions

et al. 2014

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Abstract.A unique set of images of Saturn's northern polar UV aurora was obtained by the Hubble Space Telescope in 2011 and 2012 at times when the Cassini spacecraft was located in the solar wind just upstream of Saturn's bow shock. This rare situation provides an opportunity to use the Kronian paraboloid magnetic field model to examine source locations of the bright auroral features by mapping them along field lines into the magnetosphere, taking account of the interplanetary magnetic field (IMF) measured near simultaneously by Cassini. It is found that the persistent dawn arc maps to closed field lines in the dawn to noon sector, with an equatorward edge generally located in the inner part of the ring current, typically at ∼ 7 Saturn radii (R S ) near dawn, and a poleward edge that maps variously between the centre of the ring current and beyond its outer edge at ∼ 15 R S , depending on the latitudinal width of the arc. This location, together with a lack of response in properties to the concurrent IMF, suggests a principal connection with ring-current and nightside processes. The higher-latitude patchy auroras observed intermittently near to noon and at later local times extending towards dusk are instead found to straddle the model open-closed field boundary, thus mapping along field lines to the dayside outer magnetosphere and magnetopause. These emissions, which occur preferentially for northward IMF directions, are thus likely associated with reconnection and open-flux production at the magnetopause. One image for southward IMF also exhibits a prominent patch of very high latitude emissions extending poleward of patchy dawn arc emissions in the pre-noon sector. This is found to lie centrally within the region of open model field lines, suggesting an origin in the current system associated with lobe reconnection, similar to that observed in the terrestrial magnetosphere for northward IMF.

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“…The closed field region is contained between the red and green lines, the former being projected from the southern ionosphere and the latter from the northern, which now extends to much greater distances down the tail than for case C. These lines are connected to each other at intersections of the magnetic separator line with the equatorial plane. (For a discussion of the "open" field geometries occurring for northward-and southwarddirected IMF in these cases, corresponding to southward-and northward-directed IMF at Earth due to the differing planetary dipole directions, the reader is referred to the works of Alexeev and Belenkaya (1983) and Blomberg et al (2005), and references therein.) The blue squares again show the equatorial intersections of the equatorward boundary of the dayside oval, which as for case C is somewhat variably located between the outer edge and centre of the ring current region, ∼8.5-12.5 R S .…”

Section: Image a During Southward Imf Conditionsmentioning

confidence: 99%

Magnetospheric mapping of the dayside UV auroral oval at Saturn using simultaneous HST images, Cassini IMF data, and a global magnetic field model

et al. 2011

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Abstract.We determine the field-aligned mapping of Saturn's auroras into the magnetosphere by combining UV images of the southern dayside oval obtained by the Hubble Space Telescope (HST) with a global model of the magnetospheric magnetic field. The model is tailored to simulate prevailing conditions in the interplanetary medium, corresponding to high solar wind dynamic pressure and variable interplanetary magnetic field (IMF) strength and direction determined from suitably lagged field data observed just upstream of Saturn's dayside bow shock by the Cassini spacecraft. Two out of four images obtained in February 2008 when such simultaneous data are available are examined in detail, exemplifying conditions for northward and southward IMF. The model field structure in the outer magnetosphere and tail is found to be very different in these cases. Nevertheless, the dayside UV oval is found to have a consistent location relative to the field structure in each case. The poleward boundary of the oval is located close to the open-closed field boundary and thus maps to the vicinity of the magnetopause, consistent with previous results. The equatorward boundary of the oval then maps typically near the outer boundary of the equatorial ring current appropriate to the compressed conditions prevailing. Similar results are also found for related images from the January 2004 HST data set. These new results thus show that the mapped dayside UV oval typically spans the outer magnetosphere between the outer part of the ring current and the magnetopause. It does not encompass the region of primary corotation flow breakdown within the inner Enceladus torus.

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Transpolar aurora: time evolution, associated convection patterns, and a possible cause

Cited by 12 publications

References 59 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

Magnetospheric magnetic field modelling for the 2011 and 2012 HST Saturn aurora campaigns – implications for auroral source regions

Magnetospheric mapping of the dayside UV auroral oval at Saturn using simultaneous HST images, Cassini IMF data, and a global magnetic field model

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