ANGEO Annales Geophysicae ANGEO 1432-0576 Copernicus GmbH Göttingen, Germany 10.5194/angeo-25-99-2007 Physics of the Ion Composition Boundary: a comparative 3-D hybrid simulation study of Mars and Titan Simon S. 1 Boesswetter A. 1 Bagdonat T. 1 Motschmann U. 1 2 Institute for Theoretical Physics, TU Braunschweig, Germany Institute for Planetary Research, DLR, Berlin, Germany 01 02 2007 25 1 99 115 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.ann-geophys.net/25/99/2007/angeo-25-99-2007.html The full text article is available as a PDF file from http://www.ann-geophys.net/25/99/2007/angeo-25-99-2007.pdf

The plasma environments of Mars and Titan have been studied by means of a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. As neither Mars nor Titan possesses a significant intrinsic magnetic field, the upstream plasma flow interacts directly with the planetary ionosphere. The characteristic features of the interaction region are determined as a function of the alfvénic, sonic and magnetosonic Mach number of the impinging plasma. For the Martian interaction with the solar wind as well as for the case of Titan being located outside Saturn's magnetosphere in times of high solar wind dynamic pressure, all three Mach numbers are larger than 1. In such a scenario, the interaction gives rise to a so-called Ion Composition Boundary, separating the ionospheric plasma from the ambient flow and being highly asymmetric with respect to the direction of the convective electric field. The formation of these features is explained by analyzing the Lorentz forces acting on ionospheric and ambient plasma particles. Titan's plasma environment is highly variable and allows various different combinations of the three Mach numbers. Therefore, the Ion Composition Boundary may vanish under certain circumstances. The relevant physical mechanism is illustrated as a function of the Mach numbers in the upstream plasma flow.

 References Acu\~na, M H., Connerney, J. E P., Wasilewski, P., Lin, R P., Anderson, K A., Calson, C W., McFadden, J., Curtis, D W., Mitchell, D., Rème, H., Mazelle, C., Sauvaud, J A., d'Uston, C., Cros, A., Medale, J L., Bauer, S J., Cloutier, P., Mayhew, M., Winterhalter, D., and Ness, N F.: Magnetic field and plasma observations at Mars: Initial results of the Mars Global Surveyor Mission, Science, 279, 1676–1680, 1998. Backes, H.: Titan's Interaction with the Saturnian Magnetospheric Plasma, Ph.D. thesis, Universität Köln, 2005. Backes, H., Neubauer, F M., Dougherty, M K., Achilleos, N., André, N., Arridge, C S., Bertucci, C., Jones, G H., Khurana, K K., Russell, C T., and Wennmacher, A.: Titan's Magnetic Field Signature During the First Cassini Encounter, Science, 308, 992–995, 2005. Bagdonat, T.: Hybrid Simulation of Weak Comets, Ph.D. thesis, Technische Universität Braunschweig, 2004. Bagdonat, T. and Motschmann, U.: 3D hybrid simulation of solar wind interaction with comets, in: Space Plasma Simulation – Proceedings of the Sixth International School/ Symposium ISSS-6, edited by:~Büchner, J., ~Dum, C., and~Scholer, M., 80–83, 2001. Bagdonat, T. and Motschmann, U.: 3D Hybrid Simulation Code Using Curvilinear Coordinates, J. of Computational Physics, 183, 470–485, 2002a. Bagdonat, T. and Motschmann, U.: From a weak to a strong comet – 3D global hybrid simulation studies, Earth, Moon and Planets, 90, 305–321, 2002b. Barabash, S. and Lundin, R.: ASPERA-3 on Mars Express, Icarus, 182, 301–307, 2006. Bertucci, C., Mazelle, C., Crider, D H., Mitchell, D L., Sauer, K., Acu\~na, M H., Connerney, J E P., Lin, R P., Ness, N F., and Winterhalter, D.: MGS MAG/ER observations at the magnetic pileup boundary of Mars: draping enhancement and low frequency waves, Adv. Space Res., 33, 1938–1944, 2004. Bertucci, C., Mazelle, C., and Acu\~na, M H.: Interaction of the solar wind with Mars from Mars Global Surveyor MAG/ER observations, J. Atmos. T. Phys., 67, 1797–1808, 2005a. Bertucci, C., Mazelle, C., Acu\~na, M H., Russell, C T., and Slavin, J A.: Structure of the magnetic pileup boundary at Mars and Venus, J. Geophys. Res., 110, 1209–1217, 2005b. Bößwetter, A., Bagdonat, T., Motschmann, U., and Sauer, K.: Plasma boundaries at Mars: A 3D simulation study, Ann. Geophys., 22, 4363–4379, 2004. Brain, D A., Halekas, J S., Lillis, R., Mitchell, D L., Lin, R P., and Crider, D H.: Variability of the altitude of the Martian sheath, Geophys. Res. Lett., 32, L18203, doi:10.1029/2005GL023126, 2005. Brain, D A., Mitchell, D L., and Halekas, J S.: The magnetic field draping direction at Mars from April 1999 through August 2004, Icarus, 182, 464–473, 2006. Brecht, S., Luhmann, J G., and Larson, D J.: Simulation of the Saturnian magnetospheric interaction with Titan, J.Geophys. Res., 105, 13 119–13 130, 2000. Breus, T K., Krymskii, A M., Lundin, R., Dubinin, E M., Luhmann, J G., Yeroshenko, Y G., Barabash, S V., Mitnitskii, V Y., Pissarenko, N F., and Styashkin, V A.: The solar wind interaction with Mars: consideration of Phobos-2 mission observations of an ion composition boundary on the dayside, J.Geophys. Res., 96, 11 165–11 174, 1991. Harnett, E M. and Winglee, R M.: The influence of a mini-magnetopause on the magnetic pileup boundary at Mars, Geophys. Res. Lett., 30, 10–1, 2003. Harnett, E M. and Winglee, R M.: Three-dimensional fluid simulations of plasma asymmetries in the Martian magnetotail caused by the magnetic anomalies, J. Geophys. Res., 110, 7226–7238, 2005. Kabin, K., Gombosi, T I., DeZeeuw, D L., Powell, K G., and Israelevich, P L.: Interaction of the Saturnian magnetosphere with Titan: Results of a three-dimensional MHD simulation, J.Geophys. Res., 104, 2451–2458, 1999. Kabin, K., Israelevich, P L., Ershkovich, A I., Neubauer, F M., Gombosi, T I., DeZeeuw, D L., and Powell, K G.: Titan's magnetic wake: Atmospheric or magnetospheric interaction, J.Geophys. Res., 105, 10 761–10 770, 2000. Kallio, E. and Janhunen, P.: Ion escape from Mars in a quasi-neutral hybrid model, J. Geophys. Res., 107, 1–1, 2002. Kallio, E., Sillanpää, I., and Janhunen, P.: Titan in subsonic and supersonic flow, Geophys. Res. Lett., 31, L15 703/1–L15 703/4, 2004. Ledvina, S A. and Cravens, T E.: A three-dimensional MHD model of plasma flow around Titan, Planet. Space Sci., 46, 1175–1191, 1998. Ledvina, S A., Luhmann, J G., Brecht, S H., and Cravens, T E.: Titan's induced magnetosphere, Advances in Space Research, 33, 2092–2102, 2004. Luhmann, J G., Russell, C T., Schwingenschuh, K., and Yeroshenko, Y.: A comparison of induced magnetotails of planetary bodies: Venus, Mars and Titan, J.Geophys. Res., 96, 11 199–11 208, 1991. Lundin, R., Barabash, S., Andersson, H., Holmström, M., Grigoriev, A., Yamauchi, M., Sauvaud, J.-A., Fedorov, A., Budnik, E., Thocaven, J.-J., Winningham, D., Frahm, R., Scherrer, J., Sharber, J., Asamura, K., Hayakawa, H., Coates, A., Linder, D R., Curtis, C., Hsieh, K C., Sandel, B R., Grande, M., Carter, M., Reading, D H., Koskinen, H., Kallio, E., Riihela, P., Schmidt, W., Säles, T., Kozyra, J., Krupp, N., Woch, J., Luhmann, J., McKenna-Lawler, S., Cerulli-Irelli, R., Orsini, S., Maggi, M., Mura, A., Milillo, A., Roelof, E., Williams, D., Livi, S., Brandt, P., Wurz, P., and Bochsler, P.: Solar Wind-Induced Atmospheric Erosion at Mars: First Results from ASPERA-3 on Mars Express, Science, 305, 1933–1936, 2004. Mazelle, C., Rème, H., Sauvaud, J A., d'Uston, C., Carlson, C W., Anderson, K A., Curtis, D W., Lin, R P., Korth, A., Mendis, D A., Neubauer, F M., Glassmeier, K H., and Raeder, J.: Analysis of suprathermal electron properties at the magnetic pile-up boundary of comet P/Halley, 16, 1035–1038, 1989. Modolo, R., Chanteur, G M., Dubinin, E., and Matthews, A P.: Influence of the solar EUV flux on the Martian plasma environment, Ann. Geophys., 23, 433–444, 2005. Nagy, A F., Winterhalter, D., Sauer, K., Cravens, T E., Brecht, S., Mazelle, C., Crider, D., Kallio, E., Zakharov, A., Dubinin, E., Verigin, M., Kotova, G., Axford, W I., Bertucci, C., and Trotignon, J G.: The plasma Environment of Mars, Space Science Reviews, 111, 33–114, 2004. Ness, N., Acuna, M., Behannon, K., and Neubauer, F.: The induced magnetosphere of Titan, J. Geophys. Res., 87, 1369–1381, 1982. Neubauer, F M., Gurnett, D A., Scudder, J D., and Hartle, R E.: Titan's magnetospheric interaction, in: Saturn, edited by:~Gehrels, T. and Matthews, M S., Univ. Arizona Press, Tucson, 760–787, 1984. Rème, H., Mazelle, C., Sauvaud, J A., d'Uston, C., Froment, F., Lin, R P., Anderson, K A., Carlson, C W., Larson, D E., Korth, A., Chaizy, P., and Mendis, D A.: Electron Plasma Environment at Comet Grigg-Skjellerup: General Observations and Comparison With the Environment at Comet Halley, J. Geophys. Res., 98, 20 965–20 976, 1993. Riedler, W., Schwingenschuh, K., Lichtenegger, H., Möhlmann, D., Rustenbach, J., Weroshenko, Y., Achache, J., Slavin, J., Luhmann, J G., and Russell, C T.: Interaction of the solar wind with the planet Mars: Phobos-2 magnetic field observations, Planet. Space Sci., 39, 75–81, 1991. Sauer, K., Roatsch, T., Motschmann, U., Moehlmann, D., and Schwingenschuh, K.: Plasma boundaries at Mars discovered by the PHOBOS~2 magnetometers, Ann. Geophys., 8, 661–670, 1990. Sauer, K., Bogdanov, A., and Baumgärtel, K.: Evidence of an ion composition boundary (protonopause) in bi-ion fluid simulations of solar wind mass loading, Geophys. Res. Lett., 21, 2255–2258, 1994. Schardt, A W., Behannon, K W., Lepping, R P., Carbary, J F., Eviatar, A., and Siscoe, G L.: The outer magnetosphere, in: Saturn, edited by:~Gehrels, T. and Matthews, M S., University of Arizona Press, Tucson, 416–459, 1984. Shimazu, H.: Three-dimensional hybrid simulation of solar wind interaction with unmagnetized planets, J. Geophys. Res., 106, 8333–8342, 2001. Simon, S., Bagdonat, T., Motschmann, U., and Glassmeier, K.-H.: Plasma environment of magnetized asteroids: A 3-D hybrid simulation study, Ann. Geophys., 24, 407–414, 2006a. Simon, S., Boesswetter, A., Bagdonat, T., Motschmann, U., and Glassmeier, K.-H.: Plasma environment of Titan: A 3-D hybrid simulation study, Ann. Geophys., 24, 1113–1135, 2006b. Terada, N., Machida, S., and Shinagawa, H.: Global hybrid simulation of the Kelvin-Helmholtz instability at the Venus ionopause, J. Geophys. Res., 107, 30–1, 2002. Vennerstrom, S., Olsen, N., Purucker, M., Acu\~na, M H., and Cain, J C.: The magnetic field in the pile-up region at Mars, and its variation with the solar wind, Geophys. Res. Lett., 30, 22–1, 2003. Verigin, M I., Gringauz, K I., and Ness, N F.: Comparison of induced magnetospheres at Venus and Titan, J. Geophys. Res., 89, 5461–5470, 1984. Vignes, D., Mazelle, C., Reme, H., Acu\~na, M H., Connerney, J. E P., Lin, R P., Mitchell, D L., Cloutier, P., Crider, D H., and Ness, N F.: The Solar Wind interction with Mars: locations and shapes of the Bow Shock and the observations of the MAG/ER experiment onboard Mars Global Surveyor, Geophys. Res. Lett., 27, 49–52, 2000. Wahlund, J.-E., Boström, R., Gustafsson, G., Gurnett, D. A., Kurth, W. S., Pedersen, A., Averkamp, T. F., Hospodarsky, G. B., Persoon, A. M., Canu, P., Neubauer, F. M., Dougherty, M. K., Eriksson, A. I., Morooka, M. W., Gill, R., André, M., Eliasson, L., and Mueller-Wodarg, I.: Cassini Measurements of Cold Plasma in the Ionosphere of Titan, Science, 308, 986–989, 2005. Wolf, D A. and Neubauer, F M.: Titan's Highly Variable Plasma Environment, J. Geophys. Res., 87, 881–885, 1982. Yeroshenko, Y., Riedler, W., Schwingenschuh, K., Luhmann, J G., Ong, M., and Russell, C T.: The Magnetotail of Mars: Phobos Observations, Geophys. Res. Lett., 17, 885–888, 1990.