1. Comet 1P/Halley Multifluid MHD model for the Giotto Fly-By M. Rubin, M. R. Combi, L. K. S. Daldorff, T. I. Gombosi, K. C. Hansen, Y. Shou, V. M. Tenishev, G. Tóth, B. van der Holst, and K. Altwegg Rubin et al. 2014, ApJ, 781, 86

2. Model description Individual ion fluids with their own continuity (m i ), momentum (m i u xi, m i u yi, m i u zi ), and pressure equations (p i ) -SWp + (Origin: SW, only sinks inside the model) -H 2 O + (Origin: Photoionization of cometary neutrals) -H + (Origin: Photoionization of cometary neutrals) -separate electron pressure equation (p e →T e ) Neutral gas (analytic description) H 2 O is described by a Haser model H, H 2 is fitted to Combi (1996) Included physics : -Photoionization & dissociation, electron-impact ionization -Ion-electron recombination -Ion-neutral charge exchange (through friction term) -Lorentz-force interaction between the fluids -Elastic collision (ion-ion, ion-electron, ion-neutral, electron-neutral) -Electron heating by photoelectrons -H 2 O cooling of electrons (inelastic electron-H 2 O collisions) -UV absorption by photoionization

3. Modeled species

4. Model input

5. Results Comparison with Giotto observations Overview of the different plasma species

6. Density

7. Electron temperature

8. Magnetic field

9. Plasma velocities

10. Plasma temperatures

11. Density

12. Lorentz-force

13. Magnetic field

14. Temperatures

15. Conclusions Multifluid MHD seems to be doing a reasonable job in fitting Giotto plasma observations Co-located inner shock for cometary species Ion pile-up does not necessarily peak at the same location for the different species Solar wind absent from the innermost region Lorentz-force interaction between the fluids can be observed (non-vanishing B x component)