Hybrid code simulations of the solar wind interaction with Pluto

[1] Pluto's low gravity implies that the atmosphere is only weakly bound and that significant hydrodynamic outflow can exist. Though surface spectroscopy of Pluto has revealed methane frost, the dominant escaping neutral gas is thought to be N2. These escaping neutrals are photoionized, and the heavy ions (N2+) move away from Pluto in the direction perpendicular to the solar wind flow (i.e., nearly unmagnetized relative to the length scales of the plasma interaction region). The turning distance of the solar wind protons at the magnetic pileup boundary is large compared to the interaction region. As a result, large ion gyroradius effects determine Pluto's highly asymmetric interaction with the solar wind. We use a three-dimensional hybrid code (fluid electrons, kinetic ions) to investigate the geometry of the interaction region for a variety of possible atmospheric escape rates in anticipation of the New Horizons encounter with Pluto. We find considerable structuring in the wake region due to bi-ion waves and Kelvin-Helmholtz waves. The shock structures vary from a simple Mach cone for low escape rates (∼2 × 1026 s−1) to a full detached bow shock for large escape rates (∼2 × 1028 s−1).

[1]  Robert D. Zucker,et al.  Fundamentals of Gas Dynamics , 1985 .

[2]  T. Cravens.  Plasma processes in the inner coma , 1991 .

[3]  R. L. McNutt,et al.  Models of Pluto‧s upper atmosphere , 1989 .

[4]  T. Gombosi,et al.  Solar wind stagnation near comets , 1985 .

[5]  K. Sauer,et al.  Low-frequency electromagnetic waves and instabilities within the Martian bi-ion plasma , 1998 .

[6]  H. Rosenbauer,et al.  Giotto ion mass spectrometer measurements at comet P/Grigg-Skjellerup , 1994 .

[7]  D. Morrison,et al.  Pluto: Evidence for Methane Frost , 1976 .

[8]  Mario H. Acuna,et al.  Hybrid simulations of solar wind interaction with magnetized asteroids: General characteristics of the interaction region , 2001 .

[9]  V. Krasnopolsky,et al.  Hydrodynamic flow of N2 from Pluto , 1999 .

[10]  K. Sauer,et al.  Bow shock ‘splitting’ in bi-ion flows , 1996 .

[11]  M. Dunlop,et al.  Low‐frequency electromagnetic waves near and below the proton cyclotron frequency at the AMPTE Ba release: Relevance to comets and Mars , 1999 .

[12]  K. Sauer,et al.  Nonlinear MHD waves and discontinuities in the Martian magnetosheath. Observations and 2D bi-ion MHD simulations , 1998 .

[13]  D. Winske,et al.  Kinetic simulation of the Kelvin‐Helmholtz instability at the Venus ionopause , 1991 .

[14]  James L. Elliot,et al.  Atmospheric Structure and Composition: Pluto and Charon , 1997 .

[15]  J. Sauvaud,et al.  Electron plasma environment at comet Grigg‐Skjellerup: General observations and comparison with the environment at comet Halley , 1993 .

[16]  A. Galeev.  Plasma Processes in the Outer Coma , 1991 .

[17]  Daniel W. Swift,et al.  Use of a hybrid code to model the Earth's magnetosphere , 1995 .

[18]  R. Wiens,et al.  Solar wind interactions with Comet 19P/Borrelly , 2004 .

[19]  M. Dunlop,et al.  Proton cyclotron emission at the AMPTE Ba release , 1999 .

[20]  Douglas S. Harned,et al.  Quasineutral hybrid simulation of macroscopic plasma phenomena , 1982 .

[21]  Thomas E. Cravens,et al.  Pick‐up ions at Pluto , 1993 .

[22]  F. Neubauer,et al.  MHD modeling applied to Giotto encounter with comet P/Grigg‐Skjellerup , 1993 .

[23]  M. Dunlop,et al.  In situ magnetic field observations of the AMPTE artificial comet , 1986, Nature.

[24]  M. Kivelson,et al.  Asteroid interaction with solar wind , 1996 .

[25]  Alan T. Tokunaga,et al.  Detection of Gaseous Methane on Pluto , 1997 .

[26]  S. Brecht.  Hybrid simulations of the magnetic topology of Mars , 1997 .

[27]  A. Johnstone.  Cometary plasma processes , 1991 .

[28]  M. Dougherty,et al.  “Phobos events”—Signatures of solar wind interaction with a gas torus? , 1998 .

[29]  K. Sauer,et al.  Plasma structures at weakly outgassing comets—results from bi-ion fluid analysis , 1996 .

[30]  R. Lundin,et al.  Structuring of the transition region (plasma mantle) of the Martian magnetosphere , 1996 .

[31]  A. Coates,et al.  UKS plasma measurements near the AMPTE artificial comet , 1986, Nature.

[32]  Owen B. Toon,et al.  Hydrodynamic escape of nitrogen from Pluto , 2005 .

[33]  Eliot F. Young,et al.  Upper Limits on Gaseous CO at Pluto and Triton from High-Resolution Near-IR Spectroscopy , 2001 .

[34]  K. Sauer,et al.  The Martian Magnetosphere - A Laboratory for Bi-Ion Plasma Investigations , 1998 .

[35]  K. Glassmeier,et al.  VELOCITY SPACE DIFFUSION OF PICKUP IONS FROM THE WATER GROUP AT COMET HALLEY , 1989 .

[36]  K. Glassmeier,et al.  First results from the Giotto magnetometer experiment during the P/Grigg-Skjellerup encounter , 1993 .

[37]  P. Delamere,et al.  Momentum transfer in the combined release and radiation effects satellite plasma injection experiments: The role of parallel electric fields , 2000 .

[38]  M. Mendillo,et al.  Optical observations of the AMPTE artificial comet from the Northern Hemisphere , 1986, Nature.

[39]  H. Rosenbauer,et al.  The velocity distributions of cometary protons picked up by the solar wind , 1989 .

[40]  U. Motschmann,et al.  The Plasma Environment of Comet 67P/Churyumov-Gerasimenko Throughout the Rosetta Main Mission , 2004 .

[41]  G. Haerendel,et al.  The AMPTE artificial comet experiments , 1986, Nature.

[42]  L A Young,et al.  Surface Ices and the Atmospheric Composition of Pluto , 1993, Science.

[43]  B. Brosowski,et al.  The interaction of the solar wind with a comet , 1967 .

[44]  E. Kührt,et al.  Interaction of the Solar Wind with Weak Obstacles: Hybrid Simulations for Weakly Active Comets and for Mars , 2006 .

[45]  K. Flammer.  The Global Interaction of Comets with the Solar Wind , 1991 .

[46]  Ralph L. McNutt,et al.  Pluto's interaction with the solar wind , 1989 .

[47]  F. Neubauer.  The Magnetic Field Structure of the Cometary Plasma Environment , 1991 .

[48]  P. Delamere.  Hybrid code simulations of the solar wind interaction with Comet 19P/Borrelly , 2006 .

[49]  M. Neugebauer.  The interaction of active comets with the solar wind , 1990 .

[50]  D. Huddleston,et al.  Modeling of pickup ion distributions in the Halley cometosheath: Empirical limits on rates of ionization, diffusion, loss and creation of fast neutral atoms , 1994 .

[51]  A. Darbyshire,et al.  Plasma waves and wave—particle interactions seen at the UKS spacecraft during the AMPTE artificial comet experiment , 1986, Nature.

[52]  A. Hassam,et al.  A simulation of the December 1984 solar wind AMPTE release , 1991 .

[53]  Peter A. Delamere,et al.  Pluto's kinetic interaction with the solar wind , 2004 .

[54]  Andrew J. Watson,et al.  Stability of Pluto's atmosphere , 1982 .

[55]  V. Formisano,et al.  Pickup water group ions at Comet Grigg-Skjellerup , 1993 .

[56]  G. Haerendel.  Active plasma experiments , 1986 .

[57]  D. Koopman.  Light-ion charge exchange in atmospheric gases. , 1968 .

[58]  D. Winske,et al.  Kinetic simulations of the Kelvin-Helmholtz instability at the magnetopause , 1993 .

[59]  Daniel W. Swift,et al.  Use of a Hybrid Code for Global-Scale Plasma Simulation , 1996 .

[60]  Peter A. Delamere,et al.  Pluto's interaction with the solar wind , 1989 .

[61]  P. Delamere,et al.  A three‐dimensional hybrid code simulation of the December 1984 solar wind AMPTE release , 1999 .

[62]  Kenneth G. Powell,et al.  Three‐dimensional multiscale MHD model of cometary plasma environments , 1996 .