E. G. Shelley

Macquarie University

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R. D. Sharp

Science Research Laboratory

W. K. Peterson

University of Colorado Boulder

H. Balsiger

University of Bern

R. G. Johnson

Arizona State University

H. Rosenbauer

Max Planck Institute for Solar System Research

A. G. Ghielmetti

Lockheed Martin (United States)

S. A. Fuselier

Southwest Research Institute

D. M. Klumpar

Montana State University

R. Schwenn

Max Planck Institute for Solar System Research

R. Goldstein

University of Cambridge

Cooperative Institutions

Goddard Space Flight Center

University of California, Berkeley

University of Bern

Southwest Research Institute

Centre National de la Recherche Scientifique

Max Planck Society

University of New Hampshire

University of Michigan–Ann Arbor

Planetary Science Institute

Lockheed Martin (United States)

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Auroral Ion Acceleration and Its Relationship to Ion Composition

E. G. Shelley H. L. Collin

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Citations (16)

Solar cycle variation of some mass dependent characteristics of upflowing beams of terrestrial ions

Journal of Geophysical Research Atmospheres (1987)

H. L. Collin W. K. Peterson E. G. Shelley

Examination of the S3‐3 and DE ion composition data spread over a solar cycle indicates that some characteristics of energetic upflowing terrestrial ion beams above the auroral zone show dependence on solar cycle. At solar maximum the different ion beam mass components have comparable mean energies, and O + dominates the beam composition. The ion energies are consistent with having been acquired from the potential drop below the satellite inferred from the electron loss cone distributions. At solar minimum the beam composition is dominated by H + , but the O + has a higher mean energy and is hotter than the H + component. Also, the O + has more energy than it could itself have acquired from the potential drop. These observations are qualitatively consistent with the ion beams having acquired their energies from a parallel electric field and being partially thermalized through the two‐stream instability between the two ion species, with this effect being modulated by the beam composition.

10.1029/ja092ia05p04757

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Citations (57)

The pickup of cometary protons by the solar wind

Astronomy and Astrophysics (1987)

M. Neugebauer A. J. Lazarus K. Altwegg H. Balsiger B. E. Goldstein

The HERS detector of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3-dimensional distribution of picked-up cometary protons over a distance of about 8 million km upstream of the bow shock of comet P/Hally. The protons were observed to be elastically scattered out of their original cycloidal trajectories such that they were nonuniformly distributed over a spherical shell in velocity space. The shell radius (relative to its expected radius) and thickness increased as the bow shock was approached. Down-stream of the shock, the cometary protons could not be distinguished from the heated solar wind protons.

Bow wave

Heliosphere

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Citations (43)

Counterstreaming ion events in the magnetosphere

Journal of Geophysical Research Atmospheres (1987)

R. E. Horita E. Ungstrup E. G. Shelley R. R. Anderson R. J. Fitzenreiter

Counterstreaming ions or ions traveling simultaneously both parallel and antiparallel to the magnetic field direction have been briefly noted in the literature but have not been studied previously in depth. We have studied over 60 counterstreaming ion (CSI) events observed on the ISEE 1 satellite. Often, both oxygen and hydrogen ions at a number of energy levels are Counterstreaming, but some events show only either oxygen or hydrogen ions at one or more energy levels involved. One particularly interesting event shows only counterstreaming oxygen ions with 417 eV energy; oxygen ions of lower energy (215 eV) and higher energy (630–17,000 eV) and all the hydrogen ions between 215 and 17,000 eV energy have lower fluxes and/or nearly isotropic pitch angle distributions. This event correlates well with wave activity in the 17‐ to 100‐Hz band and is also accompanied by 200‐eV downgoing and 400‐eV upgoing electrons. Details of this and some other CSI events are presented. The CSI events were found to occur at altitudes of about 2–8 R E on L shells of about 5–12 in the evening‐to‐morning sector from about 1700 to 0900 LT; the majority of the CSI events at altitudes between 2 and 5 R E and L values from 5 to 8 involve oxygen ions, while at higher altitudes from about 5 to 8 R E and higher L values from about 8 to 12 the majority involve hydrogen ions. Some features suggest wave‐particle interaction may be involved in some CSI events.

10.1029/ja092ia12p13523

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Species dependent energies in upward directed ion beams over auroral arcs as observed with FAST TEAMS

Geophysical Research Letters (1998)

E. Möbius Lijun Tang L. M. Kistler M. Popecki E. J. Lund

Upward flowing field‐aligned ion beams over auroral arcs have been observed with the 3‐dimensional ion mass spectrograph TEAMS on FAST. We have performed a statistical study on a sample of 77 ion beams from the auroral campaign in early 1997. All observed beams contain substantial amounts of H + , He + and O + . A clear ordering of the total energies according to mass is found, with H + having the lowest and O + the highest energy. The composition varies significantly from beam to beam, with O + /H + ratios ranging from ≈ 0.1 to 10. No variation of the energy ratio between species is observed as a function of relative abundance. These results are discussed in the light of earlier observations of higher energies for O + in statistical studies of beams during solar minimum and attempts to explain this behavior in terms of beam instabilities.

Beam energy

10.1029/98gl00381

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Citations (48)

A relationship between synchronous altitude electron fluxes and the auroral electrojet

Journal of Geophysical Research Atmospheres (1975)

R. D. Sharp E. G. Shelley G. Rostoker

Simultaneous observations during four substorms are reported from the Lockheed auroral particle spectrometer on ATS 5 and the University of Alberta meridian magnetometer chain. During the four events studied there was a good correlation between the magnitude of the trapped electron fluxes in the energy range from 1.8 to 53 keV and the magnitude of the electrojet current as measured by a station in the magnetometer chain at a latitude close to that expected for the ATS conjugate point. A model electrojet is constructed based on the work of Coroniti and Kennel (1972) which gives a good absolute agreement between the two measured quantities. The results are consistent with the convection electric field's remaining approximately constant during a substantial portion of each of the substorms studied. The temporal variations of the electrojet were apparently controlled by conductivity changes in the ionosphere as determined by the precipitating auroral electrons.

Electrojet

Equatorial electrojet

10.1029/ja080i016p02319

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Citations (9)

Single Electron Recording by Self-scanned Diode Arrays

Advances in electronics and electron physics (1976)

S. B. Mende E. G. Shelley

10.1016/s0065-2539(08)61569-3

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Citations (2)

Excitation Functions ofK41+pReactions

Physical Review (1961)

R. D. Sharp L. F. Chase R. M. Friedman E. K. Warburton E. G. Shelley

The energy of some of the gamma radiation following the proton bombardment of ${\mathrm{K}}^{41}$ has been measured, and the origins of some of these gamma rays have been determined. The excitation functions of the 1.00-Mev gamma from inelastic scattering in ${\mathrm{K}}^{41}$ and the 2.16-Mev gamma from the ${\mathrm{K}}^{41}(p, \ensuremath{\alpha}\ensuremath{\gamma})$ reaction have been measured in a region between 2.3 and 3.5 Mev and approximately 50 resonances observed. The energies and absolute cross sections, and the anisotropy of the gamma radiation proceeding from some of these resonances have been measured, leading to information on the excited states in ${\mathrm{Ca}}^{42}$ at about 13-Mev excitation, including an upper limit on the average level spacing. Evidence is given to show the 100-Mev level in ${\mathrm{K}}^{41}$ is most likely a \textonehalf{}+ state in agreement with theoretical predictions.

10.1103/physrev.124.1557

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Citations (14)

<title>Imaging ion outflow in the high-latitude magnetosphere using low-energy neutral atoms</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1993)

M. Hesse Mark F. Smith F. A. Herrero A. G. Ghielmetti E. G. Shelley

The measurement of neutral atom fluxes generated by charge exchange with the Earth's geocorona has recently been shown to provide the capability to image the magnetosphere. Here we investigate neutral oxygen fluxes, produced by charge exchange from the cusp/cleft ion fountain population. Using an empirical cusp/cleft ion fountain model, an empirical variation of the geocoronal neutral hydrogen density with distance, and typical values for charge exchange cross-sections, line-of-sight integrations are performed to calculate the neutral oxygen flux at arbitrary locations in space. The resulting images are evaluated for a set of orbital positions of the proposed HI-LITE small explorer spacecraft. It is shown that the resulting neutral oxygen fluxes are high enough for imaging with a low energy neutral atom imaging instrument (ILENA) on board the spacecraft.

Energetic neutral atom

Fountain

10.1117/12.147646

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Citations (6)

Angular distributions of auroral electrons in the energy range 0.8 to 16 kev

Journal of Geophysical Research Atmospheres (1972)

G. Paschmann R. G. Johnson R. D. Sharp E. G. Shelley

Auroral particle fluxes have been measured by detectors aboard the low-altitude, polar-orbiting satellite OVI 18. Electron pitch-angle distributions in the energy range 0.8 to 16 kev are presented for a 3-month period in 1969. The distributions at all energies were found to be predominantly isotropic for intensities above a few times 106 (cm² sec ster kev)−1, independent of latitude and geomagnetic conditions. This result suggests that strong pitch-angle diffusion is almost always operating on auroral field lines at higher electron intensities. At lower intensities and energies above a few kev, fluxes in the loss cone on the average were found to decrease with decreasing pitch angles, indicating an intensity dependence of the diffusion strength. Occasionally field-aligned angular distributions were observed at electron energies below a few kev. These anisotropies are discussed on the basis of parallel electric fields in conjunction with pitch-angle scattering.

Pitch angle

Geomagnetic latitude

10.1029/ja077i031p06111

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Citations (36)