The Interaction of the Solar Wind with Mars D.A. Brain Fall AGU December 8, 2005 UC Berkeley Space Sciences Lab

Mars in Context Comets SW EarthMoon SW SW / Earth plasma Saturn plasma / SW MarsTitan Venus

40 Years of Investigation Mariner 4,6,7, Mars 2,3, Viking 1, Phobos MGS 1997-? MEX 2003-? 1st non-terrestrial bow-shock crossing bow shocks galore! sheath sampled ionosphere profiles wake/tail studied escape products measured crustal fields discovered no significant dynamo aurora discovered low-altitude heavy ions Models Gasdynamic, MHD, hybrid, empirical, multi-fluid, … Spacecraft Milestones

The Interaction Region shock foreshock Ionopause / PEB sheath MPR / mantle / … tail wake MPB / IMB / ICB / PDB / planetopause / protonopause / magnetopause / mantle boundary / “the boundary” / … Plasma sheet Compare: fields particles waves

Upstream / Shock  || Mazelle et al., 2005 Trotignon et al., 1993 Solar Wind at 1.5 AU |B| ~ 3 nT  ~ 1 cm -3 T ~ 4 eV M A ~ 10 M MS ~ 6   Small, active shock R Mars < R Venus

Sheath MPB Pile-up region Dayside Interaction PEB exobase B - turbulent Plasma - hot SW Waves - Mirror mode B - drapes, increases Plasma - heavies effect flow B - calm Plasma - cooler, w/ heavies Waves - fast magnetosonic SW e - not allowed! Same as ionopause? Collisional atmosphere Øieroset et al., 2004 Iono- sphere Usually magnetized 10 eV100 eV Mitchell et al., 2001

Nightside Interaction protons Hot oxygen Cold oxygen Little/no ionosphere Plasma sheet Kallio, 2001 Brain et al., 2005

Crustal Fields Perturb Boundaries Change Topology Crider et al., 2004 MPB AltitudeClosed Flux Tubes Brain et al., 2005

Variability Crider et al., 2003 MPB Altitude Brain et al., 2005 MPB Altitude Brain et al., 2005 Open Flux Tubes Lat Lon Westward IMF Eastward IMF Mitchell, 2003 PEB Altitude Pressure IMF Direction EUV Season

Simulations Approaches Gasdynamic, MHD, Non-ideal MHD, Hybrid, … Goals Escape, Boundaries, Topology, Ionosphere, Detailed physics, Prediction, … Brecht et al., 2004 Harnett and Winglee, 2003; 2005 Ma et al., 2004 Terada et al., 2005 Modolo et al., 2005

Escape to Space Want to Know: — Processes — Variability — Products — Quantity Measurements — Phobos — MEX Simulations neutral ion ≈ 1 ton/hr Kallio et al., 1995

Upper Atmosphere Effects Energy deposition Structure Dynamics Chemistry Aurora Leblanc et al., 2002 Brain et al., 2005 Law and Cloutier, 1997 Withers et al., 2005 Krymskii et al., 2002 ENAs SEPs EUV Vertical Field Horizontal field

Fundamental Plasma Processes reconnection potential current acceleration instabilities Espley et al., 2005

Frontiers Escape MPB Physics Auroral Physics Space Weather Asymmetries Fluid vs. Kinetic Crustal Influence ER background SW Pressure MEX Event Brain et al., 2005 Ferguson et al., 2005 Bertucci et al., 2005

Summary 1.The Martian interaction is unique and highly variable. Key factors: Planetary size, SW at 1.5 AU, crustal fields 2.Understanding the interaction helps with many “Big Picture” questions. Climate evolution; Upper atmospheric structure and dynamics; Plasma physics in the solar system and universe 3.Many outstanding questions remain. Need further analyses, measurements, and models Here’s to 40 more years!