Motion of polar cap arcs

Hosokawa, K.; Moen, J.; Shiokawa, K.; Otsuka, Yuichi

doi:10.1029/2010ja015906

Cited by 35 publications

(77 citation statements)

References 31 publications

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“…The start of motion was sometimes consistent with the direction of IMF B y (Kullen et al, 2002;Valladares et al, 1994) and was inconsistent with it in other events. This is similar to the report by Hosokawa et al (2011) for the entire RSB data base.…”

Section: Discussionsupporting

confidence: 76%

“…An event similar to those reported in this study was recently discussed by Kozlovsky et al (2009) with incoherent scatter radar data. Overall, considering other events, our data support the notion that PC arcs are predominantly a B z positive phenomenon (Rodriguez et al, 1997;Newell et al, 2009;Hosokawa et al, 2011).…”

Section: Discussionsupporting

confidence: 73%

“…In terms of general morphology, the 9 December 2007 arcs were of typical duskside features reported for the RSB measurements in the past (Shiokawa et al, 1995;Hosokawa et al, 2011). The arcs were fairly bright and the motion was relatively steady.…”

Section: Discussionmentioning

confidence: 81%

“…Hosokawa et al, 2011). We were unable to find an obvious trigger of the arcs in variations of the IMF B y and B z as well as in the solar wind dynamic pressure.…”

Section: Discussionmentioning

confidence: 84%

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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: 76%

Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 81%

“…Hosokawa et al, 2011). We were unable to find an obvious trigger of the arcs in variations of the IMF B y and B z as well as in the solar wind dynamic pressure.…”

Section: Discussionmentioning

confidence: 84%

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

et al. 2012

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“…Several observations showed that polar cap arcs can drift at relatively low velocity in the dawn-dusk direction (e.g. Ismail et al, 1977;Hosokawa et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

et al. 2012

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Abstract. On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasistationary electric field. The field-aligned potential drop is estimated to about 700 V and the upflowing ions are accompanied by a tenuous population of isotropic protons with a temperature of about 500 eV.The magnetic footpoints of the ion outflows observed by Cluster are situated in the prolongation of the polar cap arc observed by TIMED GUVI. The upflowing ion beam and the polar cap arc may be different signatures of the same phenomenon, as suggested by a recent statistical study of polar cap ion beams using Cluster data.We use Cluster observations at high altitude as input to a quasi-stationary magnetosphere-ionosphere (MI) coupling model. Using a Knight-type current-voltage relationship and the current continuity at the topside ionosphere, the model computes the energy spectrum of precipitating electrons at the top of the ionosphere corresponding to the generator electric field observed by Cluster. The MI coupling model provides a field-aligned potential drop in agreement with Cluster observations of upflowing ions and a spatial scale of the polar cap arc consistent with the optical observations by TIMED. The computed energy spectrum of the precipitating electrons is used as input to the Trans4 ionospheric transport code. This 1-D model, based on Boltzmann's kinetic formalism, takes into account ionospheric processes such as photoionization and electron/proton precipitation, and computes the optical and UV emissions due to precipitating electrons. The emission rates provided by the Trans4 code are compared to the optical observations by TIMED. They are similar in size and intensity. Data and modelling results are consistent with the scenario of quasi-static acceleration of electrons that generate a polar cap arc as they precipitate in the ionosphere. The detailed observations of the acceleration region by Cluster and the large scale image of the polar cap arc provided by TIMED are two different features of the same phenomenon. Combined together, they bring new light on the configuration of the high-latitude magnetosphere during prolonged periods of Northward IMF. Possible implications of the modelling results for optical observations of polar cap arcs are also discussed.

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Global imaging of polar cap patches with dual airglow imagers

Hosokawa

Taguchi

Shiokawa

et al. 2014

Geophysical Research Letters

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During a 2 h interval from 2240 to 2440 UT on 12 November 2012, regions of increased 630.0 nm airglow emissions were simultaneously detected by dual all‐sky imagers in the polar cap, one at Longyearbyen, Norway (78.1°N, 15.5°E) and the other at Resolute Bay, Canada (74.7°N, 265.1°E). The Resolute Bay incoherent scatter radar observed clear enhancements of the F region electron density up to 1012 m−3 within these airglow structures which indicates that these are optical manifestations of polar cap patches propagating across the polar cap. During this interval of simultaneous airglow imaging, the nightside/dawnside (dayside/duskside) half of the patches was captured by the imager at Longyearbyen (Resolute Bay). This unique situation enabled us to estimate the dawn‐dusk extent of the patches to be around 1500 km, which was at least 60–70% of the width of the antisunward plasma stream seen in the Super Dual Auroral Radar Network convection maps. In contrast to the large extent in the dawn‐dusk direction, the noon‐midnight thickness of each patch was less than 500 km. These observations demonstrate that there exists a class of patches showing cigar‐shaped structures. Such patches could be produced in a wide range of local time on the dayside nearly simultaneously and spread across many hours of local time soon after their generation.

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Motion of polar cap arcs

Cited by 35 publications

References 31 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

Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

Global imaging of polar cap patches with dual airglow imagers

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