Global Auroral Morphology: Quadrennial Report to the I.U.G.G. on U.S. Contributions

Meng, C.‐I.; Mauk, B. H.

doi:10.1002/rog.1991.29.s2.1028

Cited by 5 publications

(2 citation statements)

References 208 publications

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“…At Earth, planetward streaming observed during relatively quiet geomagnetic conditions is attributed to a distant magnetotail source (-100 R E [e.g., Williams, 1981]). Tailward streaming in the near-planet regions is thought to be a consequence of (1) the near-Earth magnetic reflection of the planetward streams (e.g., see Kane et al [1991] for some Uranian cases showing the anticipated energy dispersion for very near planet observations) and (2) the initiation of magnetic substorm activity in the near-planet magnetotail regions associated with intense auroral activity (8-25 R E at Earth; the positioning is highly controversial [Meng and Mauk, 1991]). Within the Uranian magnetotail, tailward streaming was as common as planetward streaming, and it completely predominated at distances >55 Ry.…”

Section: The Magnetotail and The Issue Of Substormsmentioning

confidence: 99%

The magnetosphere of Neptune: Hot plasmas and energetic particles

Mauk

Keath²,

Kane³

et al. 1991

J. Geophys. Res.

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A comprehensive overview is provided of the hot plasmas and energetic particles (≳keV) observed in the vicinity of Neptune by the low energy charged particle (LECP) experiment on the Voyager 2 spacecraft. The LECP data are ordered with respect to magnetic field data and models derived from the Voyager magnetometer experiment. The findings include the following: (1) Weakly enhanced ion and electron fluxes were observed at the position of the subsolar bow shock. (2) Magnetic‐field‐aligned, antiplanetward streaming ions and electrons were sporadically observed within the inbound (subsolar) and outbound (tail flank) magnetosheaths, and within the unique “pole‐on” cusp region encountered during the inbound trajectory. (3) Tangential ion streaming was observed at the positions of both the inbound (dawnward streaming) and outbound (tailward streaming) magnctopauscs. (4) A distinct “trans‐Triton” ion population outside the minimumL shell of Triton is characterized by large angular anisotropics that show that heavy ions (presumably N+) are a likely constituent This population is at least partially corotating with Neptune out to at least L = 27 RNand is also characterized at times by cigar‐shaped (field‐aligned) pitch angle distributions, possibly indicative of an interaction with a neutral torus. (5) Within the middle magnetospheric regions (inside Triton), pitch angle distributions have well‐developed trapped or “pancake” shapes. Also, in contrast to Uranus, flux profiles show no evidence of substorm‐generated azimuthal asymmetries. (6) Triton (and/or Triton‐generated neutral gas) controls the outer bounds of the hot plasmas and energetic particles, although the mechanism of that control is unclear. Also, there are clear charged particle signatures of satellite 1989NI and of ring 1989N3R. However, the large number of calculated criticalLshell positions associated with all of the rings and satellites renders impractical at this time the unique determination of causal relationships between the many observed particle signatures and known material bodies. (7) Concerning the bulk (integral) and spectral parameters of the not plasmas, if it is assumed that the trans‐Triton population is dominated by N+, the plasma β parameter reaches ∼1 within the near‐planet magnetotail (L ∼28 RN; in conjunction with a magnetic field depression “tail event”), having only reached ∼0.2 in the more planetward regions. Integral electron energy intensities are such that the more localized Neptune UV aurora can be explained if loss cone intensities are ≲1% of trapped intensities. In contrast to the Uranian magnetosphere, the lower‐energy electron distributions appear generally to be at least as well characterized by hot Maxwellian distributions (kT = 10 to 30 keV) as by power law distributions inside L ∼20 RN, a characteristic generally exhibited at the other planets by the ions. At Neptune the ions have kT = 12 to 100 keV, and kTis strongly correlated with position relative to Triton's L shell. (8) Within the Neptunian magnetotail, planetward, mag...

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Section: The Magnetotail and The Issue Of Substormsmentioning

confidence: 99%

The magnetosphere of Neptune: Hot plasmas and energetic particles

Mauk

Keath²,

Kane³

et al. 1991

J. Geophys. Res.

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“…The importance of auroral X ray arcs is that they map along magnetic field lines to distant structures in the magnetosphere, providing insight into the geometry of regions in the geomagnetic tail where energy is released. The reader is referred to the review of Meng and Mauk [ 1991] for a review of the issues surrounding these mappings.…”

Section: Precipitation Of Energetic Electrons Into the Auroral Zone Pmentioning

confidence: 99%

Kilometer scale structures in auroral X ray arcs detected by combining satellite X ray images with in situ energetic electron flux profiles

Datlowe¹,

Imhof²,

Voss³

1993

J. Geophys. Res.

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X ray images of the Earth's auroral zone give a large-scale view of the precipitation patterns of energetic electrons through the bremsstrahlung produced by the electrons stopping in the atmosphere. Here we present X ray maps based on observations by the XRIS imager on the S81-1 polar orbiting satellite; discrete X ray arcs are the most prominent features in these data. The full width half maximum spatial resolution of XRIS was 40 km, but high time resolution measurements of electrons above 16 keV could detect 2 km spatial variations in one dimension along the track of the satellite. The technique was used to study 26 auroral arcs observed in 4-40 keV X rays by the XRIS and showed that in 2/3 of the cases the full width of the precipitation region was smaller than 40 km. Furthermore, comparisons with electron data lead to the conclusion that significant spectral variations occur on kilometer size scales.

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Magnetospheres of the Earth and Planets

Axford

2003

Digital Encyclopedia of Applied Physics

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Global Auroral Morphology: Quadrennial Report to the I.U.G.G. on U.S. Contributions

Cited by 5 publications

References 208 publications

The magnetosphere of Neptune: Hot plasmas and energetic particles

The magnetosphere of Neptune: Hot plasmas and energetic particles

Kilometer scale structures in auroral X ray arcs detected by combining satellite X ray images with in situ energetic electron flux profiles

Magnetospheres of the Earth and Planets

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