Low-Energy Ion Pitch-Angle Distributions in the Outer Magnetosphere: Ion Zipper Distributions.

Fennell, J. F.; Croley, D. R.; Jr., Kaye; M., S.

doi:10.21236/ada106153

Cited by 7 publications

(11 citation statements)

References 6 publications

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“…Ion trajectory calculations show that both the ring current and warm plasma cloak ion populations can occupy the same region of space, though at different energies, with the lower‐energy warm plasma cloak ions tending to be more field aligned and mirroring at lower altitudes and the more energetic ring current being trapped closer to the equator (compare the examples in Figures 10 and 13). This is completely consistent with earlier observations [ Fennell et al , 1981] and with the previously discussed simultaneous observations of warm bidirectional field‐aligned plasma seen by TIDE and keV trapped ring current distributions seen by TIMAS (Figures 5, 6, and 7).…”

Section: Ring Current Formationsupporting

confidence: 93%

“…The ring current particles show a fairly isotropic distribution with two loss cones of about ±20 degrees, while the bidirectional field‐aligned distributions display a more magnetic field centric distribution which would mirror at an altitude of 1–8 Earth radii. This combination of ion distributions would produce the “zipper” distributions reported by Fennell et al [1981], near geosynchronous orbit. In this particular orbit, the spacecraft moves along at a nearly constant L shell and local time for close to 4 hours, from 0500 to 0900 UT.…”

Section: Tide Occurrence Probabilities Of Bidirectional Field‐alignedmentioning

confidence: 97%

“…The SCATHA (P78‐2) satellite was launched in early 1979 and carried instruments capable of measuring the ion and electron spectrum from tens of eV to tens of keV [ Stevens and Vampola , 1978], the ion composition from 1 to 50 eV [ Reasoner et al , 1982] and the ion composition from 100 eV–32 keV [ Kaye et al , 1981]. Field‐aligned low‐energy ions in the tens to hundreds of eV were found to be ubiquitous at the SCATHA orbit in the middle magnetosphere near geosynchronous orbit [ Fennell et al , 1981]. Composition measurements showed that the low‐energy field‐aligned ions were often made up of more O+ than H + which suggested an ionospheric source [ Kaye et al , 1981].…”

Section: Observations Related To the Warm Plasma Cloakmentioning

confidence: 99%

“…Composition measurements showed that the low‐energy field‐aligned ions were often made up of more O+ than H + which suggested an ionospheric source [ Kaye et al , 1981]. The ions displayed a dramatic minimum in the energy spectrum near 2–10 keV that was interpreted by Fennell et al [1981] as being a result of the different drift paths for the low‐ and high‐energy ions with the low‐energy ions drifting from the plasma sheet around the dawnside of the Earth and the higher‐energy ions drifting around the duskside and contributing to the ring current ion population.…”

Section: Observations Related To the Warm Plasma Cloakmentioning

confidence: 99%

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Observations of the warm plasma cloak and an explanation of its formation in the magnetosphere

et al. 2008

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[1] Previous studies of the magnetospheric plasma populations have concentrated on the low-energy (1 eV) plasma of the plasmasphere, the more energetic (1-100 keV) plasma of the plasma sheet and ring current, and the high-energy (approximately MeV) plasma of the radiation belts. A compilation of satellite measurements over the past 30 years augmented by recent observations from the Polar-TIDE instrument has revealed a new perspective on a plasma population in the middle magnetosphere. This population consists of ions with energies of a few eV to greater than several hundred eV which display a characteristic bidirectional field-aligned pitch angle distribution. Measurements from the ATS, ISEE, SCATHA, DE, and POLAR satellites establish the characteristics of this ''warm plasma cloak'' of particles that is draped over the nightside region of the plasmasphere and is blown into the morning and early afternoon dayside sector by the sunward convective wind in the magnetosphere. The satellite observations combined with the predictions of an ion trajectory model are used to describe the formation and dynamics of the warm plasma cloak.

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Section: Ring Current Formationsupporting

confidence: 93%

Section: Tide Occurrence Probabilities Of Bidirectional Field‐alignedmentioning

confidence: 97%

Section: Observations Related To the Warm Plasma Cloakmentioning

confidence: 99%

Section: Observations Related To the Warm Plasma Cloakmentioning

confidence: 99%

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Observations of the warm plasma cloak and an explanation of its formation in the magnetosphere

et al. 2008

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“…The fluxes of such ions are much lower than those mirroring close to the geomagnetic equatorial plane. The simple anisotropy index q (or N) is nevertheless very useful to organize the anisotropy information, particularly in the geomagnetic equatorial region on L shells below those on which L shell splitting effects are significant [Roedeter, 1979;Fennell et al, 1981], since it contains in a single parameter a measure of an entire angular distribution. In this study we have taken care to exclude locations where the sinusoidal fit is particularly poor.…”

Section: Jñ = Joñ Sinn So (2)mentioning

confidence: 99%

Anisotropy characteristics of geomagnetically trapped ions

Garcia¹,

Spjeldvik²

1985

J. Geophys. Res.

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Radiation belt ions (protons plus heavier ions) are found to exhibit quiet time pitch angle anisotropies that vary significantly and nonmonotonically with L shell and energy in the range 20 keV to several MeV. Data from two spacecraft are reported' Explorer 45 measurements obtained in June 1972 and ISEE 1 measurements obtained from November 1977 through December 1978. Both data sets show that the radial distribution of pitch angle anisotropy contains one major minimum for most energies at some midrange L shell. The 1972 data collected over a 15-day period in a localized region of the magnetosphere (between L = 2 and L = 5 in the afternoon local time sector) revealed an anisotropy profile for most energies that increased with lower L shells below L ~ 2.5, minimized near L = 3, then attained a local maximum around L ~ 4, and evolved to more isotropic distributions near the Explorer 45 orbit apogee at L = 5.2. The 1977-1978 pitch angle anisotropies observed by ISEE 1 were obtained over all local times from approximately L = 2.5 to the outer limit of trapping. These data in general tended to confirm the 1972 finding of nonmonotonic anisotropy distributions, but with some important modifications. The later quiet time distributions showed a broader region of low anisotropy and less regular L shell dependence than the 1972 data, and showed systematic trends in the anisotropy that were clearly dependent not only on L shell but also on energy. A single, major anisotropy minimum was observed at virtually every local time, the location of this minimum occurred at lower L shells with progressively increasing energy. Comparison of the two quiet time data sets separated by about 6 years suggests that there may also be an anisotropy dependence on the phase of the solar cycle, possible resulting from ion composition differences or from different wave-particle interactions.

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The inner magnetosphere ion composition and local time distribution over a solar cycle

Kistler

Mouikis

2016

JGR Space Physics

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Using the Cluster/Composition and Distribution Function (CODIF) analyzer data set from 2001 to 2013, a full solar cycle, we determine the ion distributions for H+, He+, and O+ in the inner magnetosphere (L < 12) over the energy range 40 eV to 40 keV as a function magnetic local time, solar EUV (F10.7), and geomagnetic activity (Kp). Concentrating on L = 6–7 for comparison with previous studies at geosynchronous orbit, we determine both the average flux at 90° pitch angle and the pitch angle anisotropy as a function of energy and magnetic local time. We clearly see the minimum in the H+ spectrum that results from the competition between eastward and westward drifts. The feature is weaker in O+ and He+, leading to higher O+/H+ and He+/H+ ratios in the affected region, and also to a higher pitch angle anisotropy, both features expected from the long‐term effects of charge exchange. We also determine how the nightside L = 6–7 densities and temperatures vary with geomagnetic activity (Kp) and solar EUV (F10.7). Consistent with other studies, we find that the O+ density and relative abundance increase significantly with both Kp and F10.7. He+ density increases with F10.7, but not significantly with Kp. The temperatures of all species decrease with increasing F10.7. The O+ and He+ densities increase from L = 12 to L ~ 3–4, both absolutely and relative to H+, and then drop off sharply. The results give a comprehensive view of the inner magnetosphere using a contiguous long‐term data set that supports much of the earlier work from GEOS, ISEE, Active Magnetospheric Particle Tracer Explorers, and Polar from previous solar cycles.

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Low-Energy Ion Pitch-Angle Distributions in the Outer Magnetosphere: Ion Zipper Distributions.

Cited by 7 publications

References 6 publications

Observations of the warm plasma cloak and an explanation of its formation in the magnetosphere

Observations of the warm plasma cloak and an explanation of its formation in the magnetosphere

Anisotropy characteristics of geomagnetically trapped ions

The inner magnetosphere ion composition and local time distribution over a solar cycle

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