Effect of satellite potential on direct ion density measurements through the plasmapause

Whipple, E. C.; Warnock, J. M.; Winkler, R.

doi:10.1029/ja079i001p00179

Cited by 47 publications

(17 citation statements)

References 25 publications

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“…In order to obtain a tractable problem we assume spherical symmetry. It has been shown that a spherically symmetric sheath can at times be a good approximation in the magnetosphere (see the discussion of the use of a Debye potential in the paper by Whipple et al [1974]). For the ATS 6 spacecraft, most of the secondary electrons probably come from the large 10-m-diameter parabolic reflector, which should provide a reasonably homogeneous source.…”

Section: Formulation Of the Problemmentioning

confidence: 99%

Theory of the spherically symmetric photoelectron sheath: A thick sheath approximation and comparison with the ATS 6 observation of a potential barrier

Whipple¹

1976

J. Geophys. Res.

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Photoelectrons and secondary electrons have recently been observed to have been reflected back to the ATS 6 spacecraft from a potential barrier in the spacecraft vicinity. Guernsey and Fu (1970) and others have predicted the presence of a potential barrier in a photoelectron sheath. In order to determine whether or not the observed barrier is due to the emitted electrons, a theory for a spherically symmetric sheath has been developed which includes the effects of both the emitted electrons and the ambient plasma electrons and ions. A thick sheath approximation based on an analysis of particle trajectories in phase space is obtained which is valid for large particle Debye lengths. A comparison with the ATS 6 data shows that the observed barrier potentials are too large to be explained in this way.

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Section: Formulation Of the Problemmentioning

confidence: 99%

Theory of the spherically symmetric photoelectron sheath: A thick sheath approximation and comparison with the ATS 6 observation of a potential barrier

Whipple¹

1976

J. Geophys. Res.

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“…In highly structured regions these two may not always track. In addition, the calibration coefficients (sensitivity factors), which are determined by this comparison process, are thought to be somewhat dependent on total ion density and composition, ion temperature, and spacecraft potential [Parker and Whipple, 1970;Whipple et al, 1974]. Nevertheless, these effects seem to be sufficiently small to enable the mass spectrometer to produce ion concentration measurements to better than 20% accuracy as compared with simultaneous electron concentration data, such as those obtained from the top side sounder.…”

Section: Instrument Calibrationmentioning

confidence: 99%

Initial ion composition results from the Isis 2 satellite

Hoffman¹,

Dodson²,

Lippincott³

et al. 1974

J. Geophys. Res

170

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Isis 2 satellite carried, among other ionospheric instruments, an ion mass spectrometer designed to measure the composition of the ionosphere in the mass range 1–64 amu. The satellite, in a nearly constant 1400‐km orbit, was launched on April 1, 1971. Examples of data show a wide variation in ion composition from 99% H+ at night near the equator to greater than 95% O+ (and N+) in the daytime poleward of the plasmapause. Both H+ and He+ are observed to be streaming outward from the high‐latitude regions with velocities of several kilometers per second (the polar wind), determined from phase shifts in roll modulation maximums between light and heavy ion species. During the August 1972 magnetic storm a unique ionosphere developed consisting of N+ as the dominant species between 55° and 80° invariant latitude (above the plasmapause) and N2+, NO+, and O2+ at the 10³‐cm−3 concentration level, whereas these molecular species are usually below the detection limit of 1 ion cm−3 in quiet times at this altitude.

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“…Note that wake formation as such is not exclusive to the polar cap or lobe regions [e.g., Whipple et al , , and references therein], but the combination of the two electric field measurements on board Cluster has made determination of the bulk velocity possible for the first time.…”

Section: The Cold Ion Detection Challengementioning

confidence: 99%

Estimation of cold plasma outflow during geomagnetic storms

et al. 2015

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Low‐energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space where spacecraft attain a positive charge due to solar illumination. Cold ions are therefore shielded from the satellite particle detectors. Furthermore, spacecraft can only cover key regions of ion outflow during segments of their orbit, so additional complications arise if continuous longtime observations, such as during a geomagnetic storm, are needed. In this paper we suggest a new approach, based on a combination of synoptic observations and a novel technique to estimate the flux and total outflow during the various phases of geomagnetic storms. Our results indicate large variations in both outflow rates and transport throughout the storm. Prior to the storm main phase, outflow rates are moderate, and the cold ions are mainly emanating from moderately sized polar cap regions. Throughout the main phase of the storm, outflow rates increase and the polar cap source regions expand. Furthermore, faster transport, resulting from enhanced convection, leads to a much larger supply of cold ions to the near‐Earth region during geomagnetic storms.

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Effect of satellite potential on direct ion density measurements through the plasmapause

Cited by 47 publications

References 25 publications

Theory of the spherically symmetric photoelectron sheath: A thick sheath approximation and comparison with the ATS 6 observation of a potential barrier

Theory of the spherically symmetric photoelectron sheath: A thick sheath approximation and comparison with the ATS 6 observation of a potential barrier

Initial ion composition results from the Isis 2 satellite

Estimation of cold plasma outflow during geomagnetic storms

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