IRF logo Student project work in Space Plasma Physics
Examensarbete (20 p)
Search for comet tail encounters

Student: Sofie Spjuth
Supervisor: Anders Eriksson

Swedish Institute of Space Physics, Uppsala
Department of Astronomy and Space Physics, Uppsala University


In May 1996, the Ulysses spacecraft encountered the ion tail of comet Hyakutake at very long distance, more than 3 AU from the comet (
Jones et al., Identification of comet Hyakutake's extremely long ion tail from magnetic field signatures, Nature, 404, 574-576, 2000; Gloeckler et al., Interception of comet Hyakutake's ion tail at a distance of 500 million kilometres, Nature, 404, 576-578, 2000). Assuming that the ion particles just propagate with the solar wind speed radially away from the sun, it should be possible to predict ion tail encounters for other spacecraft as well, for example Rosetta  (on which our LAP instrument could possibly detect the ion tail), using the orbital elements of the spacecraft and known comets.


This project consisted of developing software that identified such encounters, i.e. times when the spacecraft should be close to the ion tail of a comet for some reasonable solar wind speed. The software was used to predict crossings for Rosetta, and also to look for possible earlier but yet non-identified crossings for Ulysses, Cassini and planet Earth (i.e. for any Earth-orbiting spacecraft outside the magnetosphere). Part of the project was done at the Institute of Geophysics and Extraterrestrial Physics at the Technical University of Braunschweig, Germany.


A number of possible ion tail encounters for Rosetta were identified, although none of them is as good as the Ulysses encounter with Hyakutake. The best opportunity for Rosetta is a possible encounterwith the ion tail of comet Honda-Mrkos-Pajdusakova in July 2006 (figure below). A list is given below; full details can be found in the project report.


[Honda encounter]
Rosetta possible encounter with comet Honda-Mrkos-Pajdusakova, July 2006.
Click for larger figure.
last modified onThursday, 05-Oct-2006 09:42:27 CEST