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Volume 20, issue 3
Ann. Geophys., 20, 365–376, 2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: INTERBALL

Ann. Geophys., 20, 365–376, 2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Mar 2002

31 Mar 2002

Electrostatic interaction between Interball-2 and the ambient plasma. 1. Determination of the spacecraft potential from current calculations

M. Bouhram1, N. Dubouloz2,1, M. Hamelin1, S. A. Grigoriev3, M. Malingre1, K. Torkar4, M. V. Veselov5, Y. Galperin5, J. Hanasz6, S. Perraut7, R. Schreiber8, and L. V. Zinin3 M. Bouhram et al.
  • 1CETP-CNRS, 4 Avenue de Neptune, 94100 Saint-Maur, France
  • 2LPCE-CNRS, 45071 Orleans Cedex, France
  • 3Mathematical Dept., Kaliningrad State University, 236041 Kaliningrad, Russia
  • 4Space Research Institute, A. A. S., Inffeldgasse 12, A-8010 Graz, Austria
  • 5Space Research Institute, R. A. S., Profsoyuznaya 84/32, 117810 Moscow, Russia
  • 6Space Research Centre, P. A. S., ul. Rabianska 8, 87-100 Torun, Poland
  • 7CETP-CNRS, 10-12 Avenue de l’Europe, 78140 Velizy, France
  • 8N. Copernicus Astronomical Centre, P. A. S., ul. Rabianska 8, 87-100 Torun, Poland
  • Correspondence to: M. Bouhram
  • (

Abstract. The Interball-2 spacecraft travels at altitudes extending up to 20 000 km, and becomes positively charged due to the low-plasma densities encountered and the photoemission on its sunlit surface. Therefore, a knowledge of the spacecraft potential Fs is required for correcting accurately thermal ion measurements on Interball-2. The determination of Fs  is based on the balance of currents between escaping photoelectrons and incoming plasma electrons. A three-dimensional model of the potential structure surrounding Interball-2, including a realistic geometry and neglecting the space-charge densities, is used to find, through particle simulations, current-voltage relations of impacting plasma electrons Ie (Fs ) and escaping photoelectrons Iph (Fs ). The inferred relations are compared to analytic relationships in order to quantify the effects of the spacecraft geometry, the ambient magnetic field B0 and the electron temperature Te . We found that the complex geometry has a weak effect on the inferred currents, while the presence of B0 tends to decrease their values. Providing that the photoemission saturation current density Jph0 is known, a relation between Fs and the plasma density Ne can be derived by using the current balance. Since Jph0 is critical to this process, simultaneous measurements of Ne from Z-mode observations in the plasmapause, and data on the potential difference Fs  - Fp  between the spacecraft and an electric probe (p) are used in order to reverse the process. A value Jph0 ~ = 32 µAm-2 is estimated, close to laboratory tests, but less than typical measurements in space. Using this value, Ne and Fs  can be derived systematically from electric field measurements without any additional calculation. These values are needed for correcting the distributions of low-energy ions measured by the Hyperboloid experiment on Interball-2. The effects of the potential structure on ion trajectories reaching Hyperboloid are discussed quantitatively in a companion paper.

Key words. Space plasma physics (charged particle motion and acceleration; numerical simulation studies; spacecraft sheaths, wakes, charging)

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