A mechanism for the multiple brightenings of dayside poleward‐moving auroral forms

Fasel, G. J.; Lee, L. C.; Smith, Roger W.

doi:10.1029/93gl02487

Cited by 31 publications

(25 citation statements)

References 23 publications

(19 reference statements)

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“…[7] Several studies have associated transient dayside aurora, which is caused by enhanced electron precipitation in the low-altitude cusp, with ionospheric signatures of FTEs [e.g., Sandholt et al, 1986;Lockwood et al, 1989;Fasel et al, 1993;Fasel, 1995;Sandholt and Farrugia, 2007]. The transient aurora has been referred to as a poleward moving auroral form (PMAF) [Fasel et al, 1993].…”

Section: Introductionmentioning

confidence: 99%

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Plasma flow during the brightening of proton aurora in the cusp

et al. 2010

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[1] On the basis of simultaneous observations from the Super Dual Auroral Radar Network (SuperDARN), the far ultraviolet instrument on the IMAGE spacecraft, and a magnetometer installed on the east coast of Greenland, we present the characteristics of plasma flow during a westward moving proton aurora in the cusp, observed on 28 July 2000. Data with a time resolution of 12 and 25 s from SuperDARN at Þykkvibaer, Iceland, show that the flow having a poleward component, which was accompanied by a quick equatorward expansion of the flow region, occurred in the early stages (approximately 1.5 min) of the brightening. Data from the magnetometer from a ground station on the Greenland east coast, which is located a few hundred kilometers west of the radar's field of view, show perturbations that are consistent with equatorward flow overhead, coincident with the expansion. The presence of flow vectors in opposite directions suggests that vortical flow was present during the proton aurora. Evidence supporting the suggested flow pattern has been found in an event recorded by the Greenland west coast magnetometer chain and in a cusp pass of the DE 2 spacecraft in the literature. We attribute the moving proton aurora to the traveling bulge at the polar cap boundary, which is the footprint of a flux transfer event, and imply that the preexisting vortical flow may be intensified when it becomes inflow to the bulge.

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Section: Introductionmentioning

confidence: 99%

“…The transient aurora has been referred to as a poleward moving auroral form (PMAF) [Fasel et al, 1993].…”

Section: Introductionmentioning

confidence: 99%

Plasma flow during the brightening of proton aurora in the cusp

et al. 2010

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“…According to their study, the delay between successive brightenings is typically 1.5±4 min, which agrees well with the data presented here. Fasel et al (1993) propose that the rebrightening is due to patchy multiple X-line reconnection . Lysak et al (1995) note that the delay is similar to the AlfveÂ n wave transit time between the magnetopause and the ionosphere, and suggest that the successive brightenings might be due to an AlfveÂ n bounce e ect.…”

Section: Solar Wind Conditionsmentioning

confidence: 99%

Simultaneous optical and radar signatures of poleward-moving auroral forms

Thorolfsson¹,

Cerisier

Lockwood

et al. 2000

Ann. Geophys.

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Abstract. Dayside poleward moving auroral forms (PMAFs) were detected between 06:30 and 07:00 UT on December 16, 1998, by the meridian scanning photometer and the all-sky camera at Ny A Ê lesund, Svalbard. Simultaneous SuperDARN HF radar measurements permitted the study of the associated ionospheric velocity pattern. A good general agreement is observed between the location and movement of velocity enhancements (¯ow channels) and the PMAFs. Clear signatures of equatorward¯ow were detected in the vicinity of PMAFs. This¯ow is believed to be the signature of a return¯ow outside the reconnected¯ux tube, as predicted by the Southwood model. The simulated signatures of this model reproduce globally the measured signatures, and di erences with the experimental data can be explained by the simpli®ca-tions of the model. Proposed schemes of the¯ow modi®cation due to the presence of several¯ow channels and the modi®cation of cusp and region 1 ®eld-aligned currents at the time of sporadic reconnection events are shown to ®t well with the observations.

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“…High-latitude optical emissions accompanying particle precipitation have been studied extensively (Feldstein and Galperin, 1985 and references within). Fasel et al (1993) interpreted multiple brightenings of dayside poleward-moving auroral forms in terms of¯ux transfer events (FTEs) with multiple X-line reconnection, while classi®cation of dierent categories of dayside aurora according to IMF orientation was reported by Sandholt et al (1998). An example of the spatial distribution of the ionospheric plasma consistent with low-latitude reconnection was presented by Walker et al (1998) that was interpreted in terms of ion dispersion and the open/closed boundary of magnetic ®eld lines.…”

Section: Introductionmentioning

confidence: 99%

Multi-instrument probing of the polar ionosphere under steady northward IMF

et al. 2000

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Abstract. Observations are presented of the polar ionosphere under steady, northward IMF. The measurements, made by six complementary experimental techniques, including radio tomography, all-sky and meridian scanning photometer optical imaging, incoherent and coherent scatter radars and satellite particle detection, reveal plasma parameters consistent with ionospheric signatures of lobe reconnection. The optical green-line footprint of the reconnection site is seen to lie in the sunward plasma convection of the lobe cells. Downstream in the region of softer precipitation the reverse energy dispersion of the incoming ions can be identi®ed. A steep latitudinal density gradient at the equatorward edge of the precipitation identi®es the general location of an adiaroic boundary, separating the open ®eld lines of polar lobe cells from the closed ®eld of viscous-driven cells. Enhancements in plasma density to the south of the gradient are interpreted as ionisation being recon®gured as it is thrust against the boundary by the antisunward¯ow of the viscous cells near noon. Each of the instruments individually provides valuable information on certain aspects of the ionosphere, but the paper demonstrates that taken together the dierent experiments complement each other to give a consistent and comprehensive picture of the dayside polar ionosphere.

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A mechanism for the multiple brightenings of dayside poleward‐moving auroral forms

Cited by 31 publications

References 23 publications

Plasma flow during the brightening of proton aurora in the cusp

Plasma flow during the brightening of proton aurora in the cusp

Simultaneous optical and radar signatures of poleward-moving auroral forms

Multi-instrument probing of the polar ionosphere under steady northward IMF

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