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Sökning: WFRF:(Fahleson Ulf)

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  • Fahleson, Ulf, et al. (författare)
  • Ionospheric temperature and density measurements by means of spherical double probes
  • 1974
  • Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633. ; 22, s. 41-66
  • Tidskriftsartikel (refereegranskat)abstract
    • Rocket-borne double probes for electric field measurements can be intermittently operated in special, diagnostic modes involving current bias and low-impedance shunts to obtain information on the properties of the ambient ionospheric plasma along the flight path. Several such modes, and the information that they can provide, are analyzed. For example, in a low-impedance mode with asymmetric bias, the attenuation ratio (i.e. signal amplitude in this mode over the signal amplitude in the electric-field measuring mode) is in a simple way related to the electron temperature of the ambient plasma. The special surface coatings (Aquadag or vitreous carbon) normally used for electric field probes provide very homogeneous surface properties, a feature which also contributes to the reliability of the electron temperature measurements. In addition to electron temperature, the modes analyzed can be used to measure electron density and to give some information on ion temperature. The data from four rocket flights from ESRANGE are discussed in the light of these results. Electron temperature was measured in three of these flights. In all cases the temperature profile is in good agreement with theoretically predicted profiles based on the CIRA 1965 reference atmosphere and the solar illumination prevailing during the respective flights (twilight). Electron density profiles obtained by means of the double probe are in good agreement with the density measured by the Langmuir probe in the two flights for which both kinds of data are available. They are also in agreement with the electron density data available from ionosondes. Finally, pulses occurring when one of the probes passed through the rocket’s shadow, are used to determine the photoelectron yield of the probe coatings (Aquadag or vitreous carbon). The values obtained, (7 ± 3) × 10-6 A/m2 for Aquadag and (4 ± 2) × 10-6 A/m2 for vitreous carbon are in good agreement with expectations based on laboratory data and solar Lyman α radiation. © 1974.
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  • Mozer, F.S., et al. (författare)
  • Measurements of quasi-static and low-freqency electric fields with spherical double probes on the IESS-1 spacecraft
  • 1978
  • Ingår i: IEEE Trans Geosci Electron. - 0018-9413. ; GE-16, s. 258-261
  • Tidskriftsartikel (refereegranskat)abstract
    • The spherical double-probe electric-field experiment on the ISEE - 1 spacecraft is described. It is shown that the isntrument measures magnetospheric, magnetosheath, and solar wind electric fields with a sensitivity well below one mv/m. Design features and diagnostic experiments performed in orbit to understand the instrument operation are discussed.
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  • Ungstrup, E., et al. (författare)
  • Rocket-borne particle, field, and plasma observations in the cleft region
  • 1975
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 2:7, s. 345-348
  • Tidskriftsartikel (refereegranskat)abstract
    • First results of comprehensive observations of magnetic and electric fields, and ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region are reported. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Our observations of electron temperatures, electric fields and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer, which is associated with the appearance of the ‘slant E condition’ identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.
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  • Resultat 1-14 av 14

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