Measurements of the thicknesses of auroral structures

Maggs, J. E.; Davis, T. N.

doi:10.1016/0032-0633(68)90069-x

Cited by 169 publications

(127 citation statements)

References 6 publications

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“…The Dense Array consists of three imagers with different narrow (compared to all-sky view) field-of-view optics. The main scientific motivation arises from an earlier study by Knudsen et al (2001) who used All-Sky Imager (ASI) combined with even earlier TV camera observations (Maggs and Davis, 1968) to suggest that there is a gap in the distribution of auroral arc widths at around 1 km. With DAISY observations we are able to show that the gap is an instrument artifact and due to limited spatial resolution and coverage of commonly used instrumentation, namely ASIs and TV cameras.…”

mentioning

confidence: 99%

Observations of the auroral width spectrum at kilometre-scale size

et al. 2010

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Abstract. This study examines auroral colour camera data from the Canadian Dense Array Imaging SYstem (DAISY). The Dense Array consists of three imagers with different narrow (compared to all-sky view) field-of-view optics. The main scientific motivation arises from an earlier study by Knudsen et al. (2001) who used All-Sky Imager (ASI) combined with even earlier TV camera observations (Maggs and Davis, 1968) to suggest that there is a gap in the distribution of auroral arc widths at around 1 km. With DAISY observations we are able to show that the gap is an instrument artifact and due to limited spatial resolution and coverage of commonly used instrumentation, namely ASIs and TV cameras. If the auroral scale size spectrum is indeed continuous, the mechanisms forming these structures should be able to produce all of the different scale sizes. So far, such a single process has not been proposed in the literature and very few models are designed to interact with each other even though the range of their favourable conditions do overlap. All scale-sizes should be considered in the future studies of auroral forms and electron acceleration regions, both in observational and theoretical approaches.

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confidence: 99%

Observations of the auroral width spectrum at kilometre-scale size

et al. 2010

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“…Field-aligned beams with as many as five discrete beams have been observed, with each having a different velocity. An estimate of the distance traveled between consecutive FABs can be obtained by using information from 2-D distributions, sampled every 125 ms. Multiplying the spacecraft velocity of ∼4.7-4.9 km s −1 with the sampling time of 0.125 s shows that the spacecraft has traveled ∼ 590-610 m. This distance mapped to the ionosphere using the T96 model indicates that the footprint of Cluster has moved ∼ 295-305 m. This distance is very typical of the auroral arc dimensions measured by Maggs and Davis (1968). Thus, our suggestion is that the discrete beams measured by Cluster represent the separation distance between the equipotential contours in auroral arcs.…”

Section: E Lee Et Al: Relating Field-aligned Beams To Inverted-v Stmentioning

confidence: 67%

“…However, these dimensions are much larger than the dimensions of a typical aurora. Various forms of auroras optically determined from a ground-based orthicon television camera (Davis, 1966) showed that the auroral dimensions can be as small as ∼ 70 m, and most of the auroral structures have dimensions less than ∼ 1 km (Maggs and Davis, 1968). Observations by Maggs and Davis (1968) have also established that the dimensions of the aurora when not measured along the magnetic zenith direction are much larger than the actual dimensions.…”

Section: Introductionmentioning

confidence: 99%

Relating field-aligned beams to inverted-V structures and visible auroras

Lee

Parks

et al. 2015

Ann. Geophys.

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Abstract. The ion composition experiment on Cluster measures 3-D distributions in one spin of the spacecraft (4 s).These distributions often measure field-aligned ion beams (H + , He + and O + ) accelerated out of the ionosphere. The standard model of these beams relies on a quasi-static Ushaped potential model. The beams contain important information about the structure and distribution of the U-shaped potential structures. For example, a simple beam with a narrow velocity range tells us that the particles are accelerated going through a quasi-static U-shaped potential structure localized in space. A more complex beam with a large range of velocities varying smoothly (a few tens of kilometers per second to > 100 km s −1 ) tells us that the potential structure is extended and distributed along the magnetic field. The Cluster experiment has now revealed new features about the beams. Some beams are broken into many individual structures each with their own velocity. The U-shaped potential model would interpret the new features in terms of particles accelerated by narrow isolated potential structures maintained over an extended region of the magnetic field. Another interpretation is that these features arise as Cluster traverses toward the center of a small-scale U-shaped potential region detecting particles accelerated on different equipotential contours. The estimate of the distance of the adjacent contours is ∼ 590-610 m at a Cluster height of ∼ 3.5 R E . The observed dimensions map to ∼ 295-305 m in the ionosphere, suggesting Cluster has measured the potential structure of an auroral arc.

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“…The current density is then 2.9 x 10 -4 amps/m 2 . This thickness is a normal one for auroral structures; for example Maggs and Davis (1968) found a median thickness of 230 meters for a set of 581 auroral structures. On the other hand, the calculated current intensity of 2.9 x 10 -4 amp/m 2 is higher than any previously reported.…”

Section: Introductionmentioning

confidence: 97%

Field-aligned current observations in the polar cusp ionosphere

Ledley¹,

Farthing²

1974

J. Geophys. Res.

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Vector magnetic field measurements made during a sounding rocket flight in the polar cusp ionosphere show field fluctuations in the lower F region that are interpreted as being caused by the passage of the pay load through a structured field‐aligned current system. The field‐aligned currents have a characteristic horizontal scale size of about 1 km. Analysis of one large field fluctuation gives a current density of 10−4 A/m²

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Measurements of the thicknesses of auroral structures

Cited by 169 publications

References 6 publications

Observations of the auroral width spectrum at kilometre-scale size

Observations of the auroral width spectrum at kilometre-scale size

Relating field-aligned beams to inverted-V structures and visible auroras

Field-aligned current observations in the polar cusp ionosphere

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