Willi Exner

Research Fellow


Main Research Fields

  • Magnetospheres of small bodies, e.g., Mercury and Ganymede
  • Analyzing magnetic field data of BepiColombo and MESSENGER
  • Computational modeling of the magnetospheric environment
  • Exosphere interaction with surface and magnetosphere
  • Extreme solar wind condition effects on magnetospheres


  • Mercury
  • BepiColombo
  • Magnetosphere
  • Exosphere
  • Computational modeling

Ongoing collaborations

  • BepiColombo MPOMAG team: Daniel Heyner, Karl-Heinz Glassmeier, Uwe Motschmann (TU Braunschweig, Germany)
  • SHOTS modeling initiative: Sae Aizawa, Lea Griton, Shahab Fatemi, Hideyuki Usui, Federico Lavorenti
  • Solar wind modeling, ICME propagation from Sun to Spacecraft: Kazumasa Iwai, Daikou Shiota, Go Murakami, Kanya Kusano, Miyoshi Yoshizumi
  • MESSENGER MAG and FIPS teams: Jim Slavin, Gankai Poh, Ryan Dewey, Jim Raines, Austin Glass, Norberto Romanelli, Gina DiBraccio
  • Exosphere of Mercury: Liam Morrisay, Rosemary Killen


First Author:

  • Influence of Mercury’s exosphere on the structure of the magnetosphere, Journal of Geophysical Research: Space Physics, 2020, doi.org/10.1029/

  • Coronal Mass Ejection at Planet Mercury: A.I.K.E.F. Hybrid-Simulations compared to MESSENGER Data, Planetary and Space Science, 2018, doi.org/10.



  • Ion density and phase space density distribution of planetary ions Na+, O+ and He+ in Mercury’s magnetosphere, Icarus. 2022, doi.org/10.1016/j.icarus.2021.114734
    • I conducted and provided numerical hybrid model results of Mercury’s magnetosphere under average solar wind conditions to facilitate statistical comparisons with an MHD model and test-particle modeling.
  • The Mie representation for Mercury’s magnetospheric currents, Earth, Planets and Space, 2021, doi.org/10.1186/s40623-021-01536-8.
    • I conducted and provided numerical model results of Mercury’s magnetosphere under southward IMF direction to disentangle the magnetospheric current system into poloidal and toroidal components.
  • The BepiColombo Planetary Magnetometer MPOMAG: What can we Learn From the Hermean Magnetic Field?, Space Science Reviews, 2021, doi.org/10.1007/s11214-021-00822-x.
    • I conducted and provided numerical model results of Mercury’s magnetosphere with a significant sodium exosphere and showed how BepiColombo orbits will see magnetic field signatures of the sodium ions.
  • Cross-comparison of global simulation models applied to Mercury’s dayside magnetosphere, Planetary and Space Science, 2020, doi.org/10.1016/j.pss.2021.105176.
    • I took part in the managing of the SHOTS-initiative and organized the different hybrid model workgroups. I conducted and provided numerical hybrid model results of Mercury’s magnetosphere under southward IMF direction to compare it against other modeling efforts within the BepiColombo community.
  • Magnetic fields in comet 67P/Churyumov-Gerasimenko, Bulletin of the Astronomical Society of Brazil, vol.32, no.1, p. 180-181, 2020, ISSN 0101-3440.
    • I analyzed magnetic field data obtained by the ROSETTA mission and helped identify possible cometary outburst signatures.
  • The Induced Global Looping Magnetic Field on Mars, The Astrophysical Journal Letters, 2019, doi:10.3847/2041-8213/aaff6e.
    • I provided Mars related hybrid modeling and helped visualizing the complex looping magnetic field pattern.

Project/mission at ESA


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