U12A-01 INVITED

The Space Environment of Mercury: Solar Wind and IMF Modeling of Upstream Conditions

* Baker, D N daniel.baker@lasp.colorado.edu, LASP/Univ. of Colorado, 1234 Innovation Drive, Boulder, CO 80309, United States
Odstrcil, D Dusan.Odstrcil@noaa.gov, NOAA, 325 Broadway, Boulder, CO 80303, United States
Anderson, B J Brian.Anderson@jhuapl.edu, Johns Hopkins/Applied Physics Lab, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Arge, C N Nick.Arge@kirtland.af.mil, Air Force Research Laboratory, 3350 Aberdeen Ave. SE, Kirtland AFB, NM 87117, United States
Benna, M Mehdi.Benna@gsfc.nasa.gov, Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
Gloeckler, G gglo@umich.edu, Atmos., Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Raines, J M jraines@umich.edu, Atmos., Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Schriver, D dave@igpp.ucla.edu, IGPP, Univiversity of California, Los Angeles, CA 90024, United States
Slavin, J A James.A.Slavin@gsfc.nasa.gov, Heliophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, United States
Solomon, S C scs@dtm.ciw.edu, Dept. of Terres. Magnetism, Carnegie Institute of Washington, Washington, DC 20015, United States
Killen, R M rkillen@astro.umd.edu, Dept. of Astronomy, University of Maryland, College Park, MD 20742, United States
Zurbuchen, T H thomasz@umich.edu, Atmos., Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States

In order to provide a broad knowledge of the solar wind properties and also some estimate of the interplanetary magnetic field (IMF) near the planet Mercury, we have used an empirical modeling technique combined with a physics-based solar wind model. The empirical approach is the Wang-Sheeley-Arge (WSA) method that uses solar photospheric magnetic field observations (from Earth-based instruments) in order to estimate inner heliospheric boundary conditions out to about 21.5 solar radii. This information is then used as input to the global magnetohydrodynamic (MHD) model, ENLIL, which calculates solar wind velocity, density, temperature, and magnetic field strength throughout the inner heliosphere. WSA-ENLIL conditions were computed for the periods around MESSENGER's flybys of Mercury in January and October of this year. This information has been used in conjunction with MESSENGER Magnetometer measurements and available MESSENGER solar wind data to understand the context of the Mercury flyby results. The in situ spacecraft data can also be used iteratively to improve the model accuracy for inner heliospheric "space weather" purposes. More generally we show how we can estimate relatively continuously the solar wind properties near Mercury and at the cruise location of MESSENGER now, for future flybys, and toward the time of spacecraft insertion into orbit about Mercury in 2011.

U12A-02

Evidence for the Magnetic Trapping of Solar-Flare Ions from 1–8-MeV Solar Neutrons Detected with the MESSENGER Neutron Spectrometer

* Feldman, W C feldman@psi.edu, Planetary Science Institute, 1700 East Ft. Lowell, Suite 106, Tucson, AZ 85719-2395, United States
Lawrence, D J David.J.Lawrence@jhuapl.edu, Johns Hopkins University Applied Physics Laboratory, Johns Hopkins Road, Laurel, Md 20723, United States
Goldsten, J O john.goldsten@jhuapl.edu, Johns Hopkins University Applied Physics Laboratory, Johns Hopkins Road, Laurel, Md 20723, United States
Gold, R E robert.gold@jhuapl.edu, Johns Hopkins University Applied Physics Laboratory, Johns Hopkins Road, Laurel, Md 20723, United States
Baker, D N daniel.baker@lasp.colorado.edu, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, United States
Haggerty, D K dennis.haggerty@jhuapl.edu, Johns Hopkins University Applied Physics Laboratory, Johns Hopkins Road, Laurel, Md 20723, United States
Krucker, S krucker@ssl.berkeley.edu, Space Sciences Laboratory, University of California, Berkeley, CA 94720, United States
Lin, R P rplin@ssl.berkeley.edu, Space Sciences Laboratory, University of California, Berkeley, CA 94720, United States
Murphy, R J murphy@ssd5.nrl.navy.mil, E.O. Hulburt Center for Space Research, Code 7650, Naval Research Laboratory, Washington DC, 20375, United States
Nittler, L R lrn@dtm.ciw.edu, Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington DC, 20015, United States
Slavin, J A james.a.slavin@nasa.gov, NASA Goddard Space Flight Center, Code 670, Greenbelt, MD 20771,
Solomon, S C scs@dtm.ciw.edu, Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington DC, 20015, United States
Starr, R D richard.d.starr@gsfc.nasa.gov, The Catholic University of America, 620 Michigan Ave, NE, Washington DC, 20064, United States
Vilas, F fvilas@mmto.org, MMT Observatory, University of Arizona, Tucson, AZ 85721, United States
Vourlidas, A vourlidas@nrl.navy.mil, E.O. Hulburt Center for Space Research, Code 7650, Naval Research Laboratory, Washington DC, 20375, United States

Neutrons produced on the Sun during the M2 flare on 31 December 2007 were observed throughout an approximately 10-hour period at 0.48 AU by the MESSENGER Neutron Spectrometer. This flare contained multiple acceleration episodes as seen in Type III radio bursts and fine structure in the energetic-particle environment at MESSENGER. After these bursts ended, both the energetic-particle and neutron fluxes decayed smoothly to background with an e-folding decay time of 2.84 hours. The fact that this time is considerably longer than the mean life of a neutron (886 s) indicates that neutrons at the Sun must have been continuously produced. A likely explanation is that a considerable fraction of the energetic ions accelerated during the flare remained trapped on closed magnetic arcades high in the corona and were slowly pitch-angle scattered by coronal turbulence into their chromospheric loss cones. Subsequent interactions with chromospheric ions generated neutrons that scatter to form a population of upward-going albedo neutrons.

U12A-03

Extended Inner Heliospheric Source of Pickup Ions

* Gloeckler, G gglo@umich.edu, Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Zurbuchen, T H thomasz@umich.edu, Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Raines, J M jraines@umich.edu, Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Krimigis, S M Tom.Krimigis@jhuapl.edu, Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, United States
McNutt, R L ralph.mcnutt@jhuapl.edu, Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, United States
Solomon, S C scs@dtm.ciw.edu, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, United States

The Fast Imaging Plasma Spectrometer (FIPS), the plasma sensor of MESSENGER's Energetic Particle and Plasma Spectrometer, has provided unprecedented insights into the interactions of the solar wind and its inner heliospheric dust component. These novel measurements were taken on the way to and following MESSENGER's first flyby of Mercury in January 2008 and will be repeated during the second flyby in October. In addition to the previously anticipated solar wind components, we find an extended source of singly charged ions, which includes Na, Mg, Si, and Fe. The solar corona can be excluded as a source for these ion components because of the single charge of these ions. Rather, these ions are likely born near the Sun and within the inner heliosphere. We also report on the discovery of an extended source of water-group ions. Our presentation will focus on these new results and their interpretation related to inner heliospheric dust. We will also relate these measurements to pickup ion observations in the extended three-dimensional heliosphere, as measured by the Ulysses Solar Wind Ion Composition Spectrometer.

U12A-04 INVITED

Overview of magnetosphere and magnetic field observations from MESSENGER's second flyby of Mercury

* Anderson, B J brian.anderson@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Korth, H haje.korth@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Acuna, M H mario.acuna@gsfc.nasa.gov, Solar System Exploration Division, NASA GSFC, Greenbelt, MD 20771, United States
Slavin, J A james.slavin@gsfc.nasa.gov, Heliophysics Science Division, NASA GSFC, Greenbelt, MD 20771, United States
Boardsen, S A Scott.A.Boardsen@gsfc.nasa.gov, Heliophysics Science Division, NASA GSFC, Greenbelt, MD 20771, United States
Raines, J M jraines@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Zurbuchen, T H thomasz@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Gloeckler, G gglo@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Krimigis, S M Tom.Krimigis@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Ho, G C george.ho@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Gold, R E robert.gold@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
McNutt, R L ralph.mcnutt@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Solomon, S C ssc@dtm.ciw.edu, Department of Terrestrial Magnetism, Carnegie Institution of Washington, District of Columbia, DC 20015, United States
Johnson, C L cljohnson@ucsd.edu, Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4, Canada
Uno, H huno@eos.ubc.ca, Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4, Canada
Purucker, M E michael.purucker@gsfc.nasa.gov, Solar System Exploration Division, NASA GSFC, Greenbelt, MD 20771, United States

MESSENGER's second flyby of Mercury on 6 October 2008 provides the first observations of the magnetic field in the planet's western hemisphere. The second flyby is planned to achieve closest approach near 200 km altitude and 130 degrees west longitude. This encounter will provide a trajectory through the magnetosphere similar to the first flyby but in the opposite body-fixed hemisphere, allowing assessment of the axisymmetry of the planetary magnetic field. The first flyby revealed plasmas with pressures comparable to the magnetic field energy density throughout the magnetosphere for quiescent magnetospheric conditions, in particular exhibiting plasma inclusions close to the planet and a layer of plasma inside the magnetopause rotational discontinuity. In addition, ultra-low-frequency (ULF) waves were observed throughout much of MESSENGER's first Mercury encounter. The second MESSENGER encounter with Mercury offers an opportunity to assess the persistence of the magnetopause structure, the prevalence of plasma inclusions close to the planet, ULF waves, and the presence of energetic electrons as reported by Mariner 10 but absent during MESSENGER's first flyby. Observations from the Magnetometer, Fast Imaging Plasma Spectrometer, and Energetic Particle Spectrometer from the second flyby should provide new information on the dynamics and structure of Mercury's magnetosphere and additional implications for the planetary magnetic field.

U12A-05

MESSENGER Observations of Magnetic Reconnection and its Effects on Mercury's Magnetosphere

* Slavin, J A james.a.slavin@nasa.gov, Heliophysics Science Division, NASA GSFC, Code 670, Greenbelt, MD 20771, United States
Acuña, M H mario.acuna@nasa.gov, Solar System Exploration Division, NASA GSFC, Code 690, Greenbelt, MD 20771, United States
Anderson, B J Brian.Anderson@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Schriver, D dave@igpp.ucla.edu, Institute for Geophysics and Planetary Physics, University of California, Los Angeles, CA 90024, United States
Solomon, S C scs@dtm.ciw.edu, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, United States
Baker, D N Daniel.Baker@lasp.colorado.edu, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, United States
Benna, M mehdi.benna@gsfc.nasa.gov, Solar System Exploration Division, NASA GSFC, Code 690, Greenbelt, MD 20771, United States
Boardsen, S A Scott.A.Boardsen@nasa.gov, Heliophysics Science Division, NASA GSFC, Code 670, Greenbelt, MD 20771, United States
Gloeckler, G gglo@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Gold, R E robert.gold@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Ho, G C George.Ho@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Korth, H Haje.Korth@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Krimigis, S M tom.Krimigis@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
McNutt, R L Ralph.McNutt@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
Raines, J M jraines@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Sarantos, M sarantos@astro.umd.edu, Heliophysics Science Division, NASA GSFC, Code 670, Greenbelt, MD 20771, United States
Travnicek, P pavel@igpp.ucla.edu, Astronomical Institute, ASCR, Prague, 1114, Czech Republic
Zurbuchen, T H thomasz@umich.edu, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States

MESSENGER's 14 January and 6 October 2008 encounters with Mercury have provided new observations of this small magnetosphere. An area where these MESSENGER measurements may have especially great impact is magnetic reconnection and its effects on magnetospheric structure and dynamics. Reconnection between the interplanetary and planetary magnetic fields is known to control the rate of energy transfer from the solar wind and to drive magnetospheric convection. Similarly, reconnection internal to the magnetospheres is a key process in determining the manner and rate of dissipation of energy derived from the solar wind in driving electric currents, the jetting and heating of plasmas, and the acceleration of energetic particles. Particles and fields measurements from MESSENGER's first two flybys of Mercury are examined for evidence of reconnection at the day-side magnetopause and in the night-side magnetosphere and to infer the intensity of the corresponding convection. Phenomena to be investigated include flux transfer events, magnetopause structure, tail current sheet structure, and charged particle acceleration and heating. The results will be used to assess the role of reconnection in Mercury's magnetosphere and contrast its overall importance for this very small magnetosphere with what has been observed at the other planets with internal magnetic fields.

U12A-06

Observations of Mercury's Exosphere With the Mercury Atmospheric and Surface Composition Spectrometer During the Second MESSENGER Flyby

* McClintock, W E william.mcclintock@colorado.edu, University of Colorado, Laboratory for Atmospheric and Space Physics, 1234 Innovation Dr., Boulder, CO 80303, United States
Bradley, E T tbradley@physics.ucf.edu, University of Central Florida, Department of Physics, 4000 Central Florida Blvd., Orlando, FL 32816, United States
Izenberg, N R noam.izenberg@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laural, MD 20723, United States
Killen, R M rkillen@astro.umd.edu, University of Maryland, Department of Astronomy, College Park, MD 2074, United States
Kochte, M C Mark.Kochte@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laural, MD 20723, United States
Lankton, M R mark.lankton@colorado.edu, University of Colorado, Laboratory for Atmospheric and Space Physics, 1234 Innovation Dr., Boulder, CO 80303, United States
Mouawad, N mouawad@astro.umd.edu, University of Maryland, Department of Astronomy, College Park, MD 2074, United States
Sprague, A L sprague@lpl.arizona.edu, Lunar and Planetary Laboratory, The University of Arizona, 1629 University Blvd., Tucson, AZ 85721, United States
Vervack, R J Ron.Vervack@jhuapl.edu, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laural, MD 20723, United States

Mercury's surface-bounded exosphere is the interface between the planet's surface and the external stimuli that interact with it. The exosphere's composition and structure are controlled by surface, magnetosphere, solar wind, and solar irradiance processes. Prior to the MESSENGER mission the exosphere was known to contain H, He, and O from Mariner 10 observations, as well as Na, K, and Ca that were discovered during ground-based observations. Na in particular has been extensively studied since its discovery in 1985. When species are liberated from the surface with sufficient energy they can be accelerated by solar radiation pressure to form a tail that extends in the direction opposite to that of the Sun. Observations of Mercury's neutral Na tail were first reported in 2002. During MESSENGER's initial flyby of Mercury, which occurred on January 14, 2008, the Ultraviolet and Visible Spectrometer (UVVS) channel of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) made the first observations of the Na tail from space beginning at an altitude of 24,500 km behind Mercury's nightside surface and covering a region of space approximately three planet diameters tall and centered on the Sun-Mercury line. The spatial distribution of Na was seen to be asymmetric, with enhanced density occurring in the northern hemisphere. UVVS observations of Ca, which were made as the spacecraft traversed the nightside exosphere, exhibited enhanced emission toward the dawn terminator. These results suggest that the relatively high-energy source processes that give rise to species observed in the tail were localized near the northern and morning hemispheres during the flyby. On the dayside of the planet, UVVS observations of neutral H revealed an altitude distribution consistent with the "warm" (T ~ 420 K) exospheric component seen by Mariner 10. During the second flyby of Mercury, which will occur on October 6, 2008, the UVVS will be configured to measure Na, Ca, and Mg in the tail and near-planet nightside regions. On the dayside, high time-cadence measurements will be used to study the detailed altitude distribution of H at low altitudes and both H and Na at altitudes above 800 km. Because Mercury's true anomaly during the second flyby (294°) will be close to that of the first flyby (285°), differences in the composition of the tail are more likely to be the result of changes in solar wind and magnetosphere conditions than of seasonal effects.

U12A-07 INVITED

Comparison of Exospheric Observations by the Mercury Atmospheric and Surface Composition Spectrometer during the First and Second MESSENGER Flybys with Concurrent Ground-based Observations

* Killen, R M rkillen@astro.umd.edu, The University of Maryland, Dept. of Astronomy, College Park, MD 20742, United States
Mouawad, N mouawad@astro.umd.edu, The University of Maryland, Dept. of Astronomy, College Park, MD 20742, United States
McClintock, W E bill.mcclintock@lasp.colorado.edu, The University of Colorado, LASP, Boulder, CO 80303, United States
Potter, A E apotter@noao.edu, National Solar Observatory, 950 N. Cherry, Tucson, AZ 85719, United States
Bida, T A tbida@lowell.edu, Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ 86001, United States
Vervack, R J ron.vervack@jhuapl.edu, The Johns Hopkins University Applied Physics Lab., 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
Bradley, E T tbradley@physics.ucf.edu, University of Central Florida, Physics Dept., Orlando, FL 32816, United States
Sprague, A L sprague@lpl.arizona.edu, Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, United States
Izenberg, N R noam.izenberg@jhuapl.edu, The Johns Hopkins University Applied Physics Lab., 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
Kochte, M C Mark.Kochte@jhuapl.edu, The Johns Hopkins University Applied Physics Lab., 11100 Johns Hopkins Rd., Laurel, MD 20723, United States
Lankton, M R Mark.Lankton@lasp.colorado.edu, The University of Colorado, LASP, Boulder, CO 80303, United States

Ground-based observations of Mercury's sodium exospheric emission were obtained at the McMath-Pierce Solar Telescope at Kitt Peak, Arizona, concurrently with the observations from the Ultraviolet and Visible Spectrometer (UVVS) on the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument onboard the MESSENGER spacecraft during the first flyby of the planet, January 14, 2008, and three weeks after the second flyby on October 6, 2008. During the first flyby the UVVS observed Na in the tail and nightside exosphere, and Ca in the dawn and nightside exosphere. Similar observations are planned for the second flyby. These will be compared with ground-based observations of calcium obtained at the Keck telescope with the HIRES spectrometer. Of particular interest is the morphology of the exosphere, which has been observed to be highly asymmetric and variable, at times to be peaked near the subsolar point and at other times peaked at one or both poles. The UVVS observations of the sodium tail revealed a N/S asymmetry near the planet during the first flyby. The cause of the high-latitude enhancements in the sodium exosphere has been variously ascribed to solar wind ion impacts, to radiation pressure, to inherent surface compositional and physical differences, and to cold trapping. The first and second flybys of MESSENGER are both near conditions of maximum radiation pressure for the inbound (towards the Sun) part of the orbit, while observations on October 27 - 30 span the maximum radiation pressure conditions for the outbound leg of the orbit. The effective radiation pressure is greatest on the outbound leg. Observations of the sodium tail will help determine the source of the energetic sodium. In-situ observations of the surface and magnetospheric environment will constrain the variations due to compositional differences and sputtering yield, respectively. Over the course of the mission, a goal is to determine the partitioning of Na and other species between the thermal and non-thermal components to determine or constrain the desorption processes from surface materials.

U12A-08

Insights into the Ion Composition and Plasma Environment of Planet Mercury from MESSENGER

* Zurbuchen, T H thomasz@umich.edu, Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Raines, J M jraines@umich.edu, Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Gloeckler, G gglo@umich.edu, Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, United States
Krimigis, S M tom.krimigis@jhuapl.edu, Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, United States
McNutt, R L Ralph.McNutt@jhuapl.edu, Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, United States
Solomon, S C scs@dtm.ciw.edu, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, United States

MESSENGER has provided the first measurements of the composition and dynamic properties of ions near Mercury. Here, we focus on observations made with the Fast Imaging Plasma Spectrometer (FIPS), the plasma sensor of the Energetic Particle and Plasma Spectrometer (EPPS) instrument, during MESSENGER's first two flybys of Mercury. This instrument has a near-hemispheric instantaneous field of view and provided plasma and compositional parameters for particles from 50 eV to 20 keV per charge throughout the first MESSENGER flyby on January 14, 2008, as it is expected to do as well during the second flyby on October 6, 2008. We first discuss the global distribution of plasma in Mercury's environment. We then report compositional measurements and spatial distributions of heavy ions, with mass up to Fe, originating from Mercury. We particularly focus on the distribution of Na and water-group ions. Finally, we discuss doubly charged ions and the implications of these results for our understanding of the intensive solar wind interaction with Mercury's surface.

Authors (2008), Title, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract xxxxx-xx