Space Science Reviews

, Volume 126, Issue 1, pp 239–266

IMF Direction Derived from Cycloid-Like Ion Distributions Observed by Mars Express

  • M. Yamauchi
  • Y. Futaana
  • A. Fedorov
  • E. Dubinin
  • R. Lundin
  • J.-A. Sauvaud
  • D. Winningham
  • R. Frahm
  • S. Barabash
  • M. Holmstrom
  • J. Woch
  • M. Fraenz
  • E. Budnik
  • H. Borg
  • J. R. Sharber
  • A. J. Coates
  • Y. Soobiah
  • H. Koskinen
  • E. Kallio
  • K. Asamura
  • H. Hayakawa
  • C. Curtis
  • K. C. Hsieh
  • B. R. Sandel
  • M. Grande
  • A. Grigoriev
  • P. Wurz
  • S. Orsini
  • P. Brandt
  • S. Mckenna-Lawler
  • J. Kozyra
  • J. Luhmann
Article

DOI: 10.1007/s11214-006-9090-1

Cite this article as:
Yamauchi, M., Futaana, Y., Fedorov, A. et al. Space Sci Rev (2006) 126: 239. doi:10.1007/s11214-006-9090-1

Abstract

Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser (IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF is relatively uniform on a scale larger than the proton gyroradius. During bow shock outbound crossings, MEX often observed cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most likely newly ionized hydrogen atoms, which are picked up by the solar wind.

Keywords

IMFMarsion gyrationpick-up process

Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • M. Yamauchi
    • 1
  • Y. Futaana
    • 1
    • 7
  • A. Fedorov
    • 2
  • E. Dubinin
    • 3
  • R. Lundin
    • 1
  • J.-A. Sauvaud
    • 2
  • D. Winningham
    • 4
  • R. Frahm
    • 4
  • S. Barabash
    • 1
  • M. Holmstrom
    • 1
  • J. Woch
    • 3
  • M. Fraenz
    • 3
  • E. Budnik
    • 2
  • H. Borg
    • 1
  • J. R. Sharber
    • 4
  • A. J. Coates
    • 5
  • Y. Soobiah
    • 5
  • H. Koskinen
    • 6
    • 17
  • E. Kallio
    • 6
  • K. Asamura
    • 7
  • H. Hayakawa
    • 7
  • C. Curtis
    • 8
  • K. C. Hsieh
    • 8
  • B. R. Sandel
    • 9
  • M. Grande
    • 10
  • A. Grigoriev
    • 1
  • P. Wurz
    • 11
  • S. Orsini
    • 12
  • P. Brandt
    • 13
  • S. Mckenna-Lawler
    • 14
  • J. Kozyra
    • 15
  • J. Luhmann
    • 16
  1. 1.Swedish Institute of Space PhysicsKirunaSweden
  2. 2.Centre d’Etude Spatiale des RayonnementsToulouseFrance
  3. 3.Max-Planck-Institut für SonnensystemforschungKatlenburg-LindauGermany
  4. 4.Southwest Research InstituteSan AntonioUSA
  5. 5.Mullard Space Science LaboratoryUniversity College LondonSurreyUK
  6. 6.Finnish Meteorological InstituteHelsinkiFinland
  7. 7.Institute of Space and Astronautical ScienceSagamicharaJapan
  8. 8.Department of PhysicsUniversity of ArizonaTucsonUSA
  9. 9.Lunar and Planetary LabUniversity of ArizonaTucsonUSA
  10. 10.Rutherford Appleton LaboratoryOxfordshireUK
  11. 11.University of Bern, Physikalisches InstitutBernSwitzerland
  12. 12.Instituto di Fisica dello Spazio InterplanetariRomeItaly
  13. 13.Applied Physics LaboratoryJohns Hopkins UniversityLaurelUSA
  14. 14.Space Technology Ltd.National University of IrelandMaynoothIreland
  15. 15.Space Physics Research Lab.University of MichiganAnn ArborUSA
  16. 16.Space Science Lab.University of California in BerkeleyBerkeleyUSA
  17. 17.Department of Physical SciencesUniversity of HelsinkiHelsinkiFinland