Fine-scale structures in auroral arcs: An unexplained phenomenon

Borovsky, Joseph E.

doi:10.1029/gm086p0255

Cited by 6 publications

(4 citation statements)

References 108 publications

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“…The goal of understanding "filamentary structure" in the aurora has arisen as a distinct quest in auroral physics, based partly on this technological progression. The lower minimum spatial scale perpendicular to the ambient magnetic field appears to be 70∼90 m (Maggs and Davis 1968;Borovsky 1995;. This limit corresponds to the electron inertial length near the density minimum in the near-Earth magnetosphere, suggesting that inertial Alfvén wave dispersion plays an important role in producing these structures (e.g., Stasiewicz et al 2000aStasiewicz et al , 2000b.…”

Section: Filamentsmentioning

confidence: 99%

“…The appearance of these Alfvénic relationships between these features and the particle source populations remains poorly understood. Borovsky (1995) once concluded that "Existing auroral-arc theories do not explain the finescale structures because none of these theories will allow a structure as narrow as the observed finescale structures". Indeed, the thesis put forth by Borovsky (1995) appears to still hold.…”

Section: Packetsmentioning

confidence: 99%

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Small-Scale Dynamic Aurora

et al. 2021

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Small-scale dynamic auroras have spatial scales of a few km or less, and temporal scales of a few seconds or less, which visualize the complex interplay among charged particles, Alfvén waves, and plasma instabilities working in the magnetosphere-ionosphere coupled regions. We summarize the observed properties of flickering auroras, vortex motions, and filamentary structures. We also summarize the development of fundamental theories, such as dispersive Alfvén waves (DAWs), plasma instabilities in the auroral acceleration region, ionospheric feedback instabilities (IFI), and the ionospheric Alfvén resonator (IAR).

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Section: Filamentsmentioning

confidence: 99%

Section: Packetsmentioning

confidence: 99%

Small-Scale Dynamic Aurora

et al. 2021

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“…The presence of auroral rays scale structures of the order of 100 m are, even in the case ß diverging away from the vortices may be an indication that of ordinary auroral forms, a still unexplained phenomenon the vortex street array was located at a very high altitude. [Borovsky, 1995].…”

Section: Black Arcsmentioning

confidence: 99%

High‐resolution television observations of black aurora

Trondsen¹,

Cogger²

1997

J. Geophys. Res.

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Abstract. In view of a recent revival of interest in the black aurora and related phenomena, and a striking lack of information on the phenomenon in the literature, we present high spatial and temporal resolution optical observations of the black aurora made by the University of Calgary portable auroral imager. A variety of black auroral phenomena, such as black vortices, arcs, and eastward drifting black auroral patches and arc segments, were observed in the evening and midnight sector diffuse auroral oval during a field trip to Rabbit Lake, Saskatchewan, from February 25 to March 7, 1995. Observed spatial and temporal characteristics are reviewed, with statistical data presented in the form of histograms.

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“…This is the smallest-known spatial scale in the visible aurora, on the order of 100 m--resolved only by a high-resolution imager carefully aligned to the direction of the local magnetic field. Remarkably, auroral fine-scale structures are still largely unexplained [Borovsky, 1995].…”

Section: Introductionmentioning

confidence: 99%

Asymmetric multiple auroral arcs and inertial Alfvén waves

Trondsen

Cogger

Samson

1997

Geophysical Research Letters

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Abstract. High-resolution optical observations by the University of Calgary Portable Auroral Imager show a frequent occurrence of asymmetric multiple small-scale auroral arc structures during auroral substorms. Whereas the classical multiple arc array tends to exhibit a fairly symmetrical configuration, with parallel motions within individual discrete arcs being opposite in direction across the center of the arc array, the multiple arcs to be discussed herein are distinguished by the presence of discrete arcs strictly equatorward of the two bright counter-streaming arcs that would ordinarily define the center of the arc array. The intensity of these parallel equatorward-lying arcs were in most cases found to decrease rapidly in the equatorward direction. By considering the topology of the structures and the spacing between arcs, observations are found to be consistent with recent theories suggesting inertial Alfv6n waves as a possible cause of fine-scale auroral arcs.

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Fine-scale structures in auroral arcs: An unexplained phenomenon

Cited by 6 publications

References 108 publications

Small-Scale Dynamic Aurora

Small-Scale Dynamic Aurora

High‐resolution television observations of black aurora

Asymmetric multiple auroral arcs and inertial Alfvén waves

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