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INSTITUTET FÖR RYMDFYSIK UPPSALA
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Swedish Institute of Space Physics (59o50.272'N, 17o38.786'E)
Student project at IRF Uppsala

Project work / Examensarbete (30 hp)

Numerical modelling of Langmuir probe measurements in space

Student: Marco Chiaretta, Uppsala University
Supervisor: Anders Eriksson
Period: 2010

Abstract

This work studies the current collected by the spherical Langmuir probes to be mounted on the ESA Swarm satellites in order to quantify deviations from ideal- ized cases caused by non-ideal probe geometry. The finite-element particle-in-cell code SPIS is used to model the current collection of a realistic probe, including the support structures, for two ionospheric plasma conditions with and without drift velocity. SPIS simulations are verified by comparing simulations of an ideal sphere at rest to previous numerical results by Laframboise parametrized to suf- ficient accuracy. It is found that for probe potentials much above the equivalent electron temperature, the deviations from ideal geometry decrease the current by up to 25 % compared to the ideal sphere case and thus must be corrected if data from this part of the probe curve has to be used for plasma density derivations. In comparison to the non-drifting case, including a plasma ram flow increases the current for probe potentials around and below the equivalent ion energy, as the contribution of the ions to the shielding is reduced by their high flow energy.

Project

In the project, the measurements by the Swarm Langmuir probes, provided by our group, were simulated for typical and extreme ionospheric plasma conditions by use of the SPIS code package for s/c-plasma interaction studies. The project included:
  • Gathering background information on Swarm, LP and the SPIS code
  • Setting up and running SPIS
  • Creating a model of the Swarm LP in SPIS
  • Running simulations and anlyzing the results
  • Project extensions to Swarm, Cassini and/or Rosetta
  • Report writing
  • Presentation of the results at the SPINE meeting at ESA Headquarters in Paris, 23 March 2010
  • Presentation at an institute seminar

Report

PDF (final version, March 18, 2011; 25.1 MB)


[SPIS plot]
Charge density around a Langmuir probe in a flowing plasma as simulated in SPIS.

https://www.space.irfu.se/exjobb/2009_marco_chiaretta/index.html
last modified on Friday, 18-Mar-2011 17:48:13 CET