IRF logo Student internship project in Space Plasma Physics (2006)
Simulating the Cluster satellites in a cold plasma flow

Student: Ram Prakash, Technical University of Delft
Supervisor: Anders Eriksson
Swedish Institute of Space Physics, Uppsala


Abstract. A good understanding of the spacecraft-plasma interaction is particularly important in the case of satellites intended for measuring the electromagnetic characteristics of the space environment. This would facilitate a prior estimate of the induced errors in onboard measurements so that the undisturbed true values can be deduced from that. Spacecraft, when in the regions of Earth's magnetospheric tail lobes and in the polar cap, encounter very tenuous plasma and become positively charged due to the photoelectron emission. In such an environment, the kinetic energy of ions wouldn't be sufficient to reach the spacecraft and instead the ion would flow around an equipotential surface from the spacecraft. This would result in an enhanced wake behind the potential obstacle, with dimensions far exceeding that of the spacecraft. The wake potentials would be much lower than the free stream potential, resulting in an erroneous measurement, if any of the instruments onboard happened to be inside the wake. A good proof for this is evident in the measurements made by Cluster satellites, where the EFW instrument has detected an apparent electric field. In this project, we have used the new open source simulation code SPIS (Spacecraft Plasma Interaction Software), to numerically simulate the spacecraft-plasma interaction. The results verified the existence of such an enhanced wake behind the satellite, while operating in the mentioned regions, and also show good agreement with the observational data from Cluster satellites.

 Ion density from SPIS simulation
Example plot from a simulation, showing the formation of an ion wake behind the booms of a Cluster satellite.

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last modified onWednesday, 11-Jul-2007 11:50:01 CEST