DOCSLIB.ORG

Solar Radiation and the Solar Wind • External Sources of Neutral Gas Or Plasma

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Solar Radiation and the Solar Wind • External Sources of Neutral Gas Or Plasma Exploration of the Solar System: A Long Way in a Short While: • When New Horizons reaches Pluto in 2016, we will have visited all of the objects we call ‘planets’. • The time from first to last is 55 years! Less than one human lifetime. (if we don’t count Pluto we were done in only 26 years) • Each planet has its own challenges (and targets) for study that make them unique. • We’ll explore the planets briefly during the rest of the class, including a focus on both their SPACE environments and the challenges we face in exploring them. Space Environment? • We define the space environment as that part of a planet-system that is controlled not from pure solar heating, but from energy/matter coming in from the outside. • There are 4 major factors that determine the characteristics of a space environment. • Magnetic Field (intrinsic/induced/external) • Atmosphere/Ionosphere/Exosphere • Solar Radiation and the Solar Wind • External Sources of Neutral Gas or Plasma • Every planet (and planet satellite) has its own unique combination of these factors controlling the space environment. Mercury: • Mercury is the smallest of all the ‘planets’, less sizable (but much more massive!) than two outer solar system icy moons. Mercury: • Mercury is the densest object in the solar system. • It’s core is composed of mainly Iron and is 65% of the diameter of the planet! • The surface of Mercury is most like that of the Moon. It’s very old and crater scarred. • However the Moon is rock-based object that has the least in common with Mercury’s interior. Mercury: • Mercury’s core double the relative size of the Earth’s. • What happened? • Volatile Stripping in the Protosun? • High Formation Temperatures for planetesimals and protoplanets? • A Giant Collision? Evolution: • The early history of Mercury had some spectacular impacts. • The Caloris Basin (left) • Left a visible scar on the far side of the planet! Evolution: • The early history of Mercury had some spectacular impacts. • The interior of Mercury appears to have cooled. • As with some icy bodies this cooling contracted the interior and left cracks on the surface. A Year and a Day: • Mercury is about 38% as far from the Sun as the Earth. • The Sun exerts strong tidal forces on Mercury. • The result is that Mercury has become ‘tidally locked’ to the Sun. • Each ‘year’ on Mercury (88 days) is 3 2 Exactly 1.5 ‘days’ (59 days) long! • This means that a night on Mercury 4 is very long, and, with no air to 1 circulate heat, VERY cold. 7 • Mercury has the largest day-night temperature swings in the solar 5 system – 600 K! 6 Atmosphere: • The atmosphere of Mercury is not like that of Earth or Mars. • The reason has to do with the smaller gravity of Mercury and its very high daytime temperature. • What you feel as temperature is actually T motion of gas particles. They hotter they are Vgas the faster they move and the greater their M momentum. • If a gas has an average speed close to the escape velocity, then it will leak away! • Heavier gasses are slower and more easily held (the Earth has Oxygen, but not Hydrogen…. ) • Mercury’s escape velocity is 4.25 km/sec and it is very hot (700K). It doesn’t hold any gasses! Atmosphere: • Because it can’t hold an atmosphere, the surface pressure of Mercury is very low. • However, it does posses a slowly evaporating exosphere of gasses that are slowly leaking away. • These gasses make up a corona around the planet, that contains, Hydrogen, Neon, Sodium, Oxygen, and Potassium. Magnetosphere: • One of the most startling features of the Mercury system is the presence of a magnetic field. • Unlike the Earth’s dynamo field, Mercury’s is ‘Frozen In’ like a bar magnet. • This field traps any of the ‘atmosphere’ that is ionized and also forms a shock boundary with the Solar Wind (very strong at 0.38 AU). • The Solar wind interaction stretches out Mercury’s field into a long ‘magnetotail’ in the anti-sunward direction. Some solar wind plasma is able to leak into the magnetosphere. This also happens near the poles. Ice!: • Another very bizarre aspect of Mercury is the possible presence of ice at its poles! • Radar images show regions of high reflectivity near the polar regions that are consistent with substantial icy deposits. Incoming Sunlight Ice • At the poles, deep craters are in permanent shadow. Things are never warm enough for evaporation of the ice to occur. Challenges: • We have only visited Mercury once (Mariner 10). • We still have only a partial map of its surface. • There are two big challenges to going back. • The most obvious is temperature. • The most difficult is velocity! • A spacecraft from the Earth is moving much too fast to enter orbit. • How do we slow down? • Two missions are headed there in the next decade! Messenger: • MESSENGER is a NASA mission to study the geology of Mercury and to complete our map of the surface. • Messenger has to use Earth and Venus to slow down. This will keep it from entering orbit until 2011. • To protect itself, MESSENGER hides behind a heat shield. BepiColombo: • BEPICOLOMBO is an ESA mission to Mercury that will launch in 2013 (after the completion of MESSENGER’s mission). • BEPICOLOMBO will actually consist of two spacecraft with different missions. • The Mercury Planetary Orbiter will study the atmosphere, surface and close-in magnetic field. • The Mercury Magnetospheric Orbiter will study the interaction between the solar wind, Mercury’s magnetic field and atmosphere..
Load more

Recommended publications
  • Shallow Crustal Composition of Mercury As Revealed by Spectral Properties and Geological Units of Two Impact Craters
    Planetary and Space Science 119 (2015) 250–263 Contents lists available at ScienceDirect Planetary and Space Science journal homepage: www.elsevier.com/locate/pss Shallow crustal composition of Mercury as revealed by spectral properties and geological units of two impact craters Piero D’Incecco a,n, Jörn Helbert a, Mario D’Amore a, Alessandro Maturilli a, James W. Head b, Rachel L. Klima c, Noam R. Izenberg c, William E. McClintock d, Harald Hiesinger e, Sabrina Ferrari a a Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, D-12489 Berlin, Germany b Department of Geological Sciences, Brown University, Providence, RI 02912, USA c The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA d Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA e Westfälische Wilhelms-Universität Münster, Institut für Planetologie, Wilhelm-Klemm Str. 10, D-48149 Münster, Germany article info abstract Article history: We have performed a combined geological and spectral analysis of two impact craters on Mercury: the Received 5 March 2015 15 km diameter Waters crater (106°W; 9°S) and the 62.3 km diameter Kuiper crater (30°W; 11°S). Using Received in revised form the Mercury Dual Imaging System (MDIS) Narrow Angle Camera (NAC) dataset we defined and mapped 9 October 2015 several units for each crater and for an external reference area far from any impact related deposits. For Accepted 12 October 2015 each of these units we extracted all spectra from the MESSENGER Atmosphere and Surface Composition Available online 24 October 2015 Spectrometer (MASCS) Visible-InfraRed Spectrograph (VIRS) applying a first order photometric correc- Keywords: tion.
    [Show full text]
  • Arxiv:2012.11628V3 [Astro-Ph.EP] 26 Jan 2021
    manuscript submitted to JGR: Planets The Fundamental Connections Between the Solar System and Exoplanetary Science Stephen R. Kane1, Giada N. Arney2, Paul K. Byrne3, Paul A. Dalba1∗, Steven J. Desch4, Jonti Horner5, Noam R. Izenberg6, Kathleen E. Mandt6, Victoria S. Meadows7, Lynnae C. Quick8 1Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA 2Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 3Planetary Research Group, Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA 4School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA 5Centre for Astrophysics, University of Southern Queensland, Toowoomba, QLD 4350, Australia 6Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA 7Department of Astronomy, University of Washington, Seattle, WA 98195, USA 8Planetary Geology, Geophysics and Geochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA Key Points: • Exoplanetary science is rapidly expanding towards characterization of atmospheres and interiors. • Planetary science has similarly undergone rapid expansion of understanding plan- etary processes and evolution. • Effective studies of exoplanets require models and in-situ data derived from plan- etary science observations and exploration. arXiv:2012.11628v4 [astro-ph.EP] 8 Aug 2021 ∗NSF Astronomy and Astrophysics Postdoctoral Fellow Corresponding author: Stephen R. Kane, [email protected] {1{ manuscript submitted to JGR: Planets Abstract Over the past several decades, thousands of planets have been discovered outside of our Solar System. These planets exhibit enormous diversity, and their large numbers provide a statistical opportunity to place our Solar System within the broader context of planetary structure, atmospheres, architectures, formation, and evolution.
    [Show full text]
  • Revisions to the Online Textbook Exploring the Planets (Explanet.Info): Mercury and Pluto
    49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083) 2724.pdf REVISIONS TO THE ONLINE TEXTBOOK EXPLORING THE PLANETS (EXPLANET.INFO): MERCURY AND PLUTO. B.C. Spilker1, E.H. Christiansen1, and J. Radebaugh1, 1Brigham Young University, De- partment of Geological Sciences, Provo, UT 84602. [email protected] Introduction: Exploring the Planets (http://ex- planet.info) [1] is a free online college textbook cover- ing the basic concepts of planetary science, and the character and evolution of the planetary bodies in the Solar System (including the planets, important moons, asteroids, and Kuiper Belt Objects). The latest edition (3rd edition) was published online in 2007 by Eric H Christiansen. Earlier paper editions were published by Prentice Hall in 1990 and 1995. Exploring the Planets approaches an introductory study of the solar system mainly through basic geolog- ical principles. Compared with other introductory plan- etary geology texts, such as Planetary Sciences by de Pater and Lissauer [2], Introduction to Planetary Sci- ence by Faure and Mensing [3], The New Solar System by Beatty, Petersen, and Chaikin [4] or Earth, Evolu- tion of a Habitable World by Lunine [5], this is the only book with a basic geology approach. It is intended to be used as a primary or supplementary source in in- troductory science courses (geology or astronomy ). Book Structure: Exploring the Planets is divided into three sections. The first section gives a broad over- view of the Solar System and an introduction to plane- tary science. This section helps the reader develop the geological background required to understand the pro- cesses that have shaped the planets, and to begin think- ing like a planetary scientist.
    [Show full text]
  • Thomas Robert Watters
    THOMAS ROBERT WATTERS Address: Center for Earth and Planetary Studies National Air and Space Museum Smithsonian Institution P. O. Box 37012, Washington, DC 20013-7012 Education: George Washington University, Ph.D., Geology (1981-1985). Bryn Mawr College, M.A., Geology (1977-1979). West Chester University, B.S. (magna cum laude), Earth Sciences (1973-1977). Experience: Senior Scientist, Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution (1998-present). Chairman, Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution (1989-1998). Research Geologist, Center for Earth and Planetary Studies, Smithsonian Institution, Planetary Geology and Tectonics, Structural Geology, Tectonophysics (1981-1989). Research Assistant, Department of Terrestrial Magnetism, Carnegie Institution of Washington, Chemical Analysis and Fission Track Studies of Meteorites (1980-1981). Research Fellowship, American Museum of Natural History, Electron Microprobe and Petrographic Study of Aubrites and Related Meteorites (1978-1980). Teaching Assistant, Bryn Mawr College (1977-1979), Physical and Historical Geology, Crystallography and Optical Crystallography. Undergraduate Assistant, West Chester University (1973-1977), Teaching Assistant in General and Advanced Astronomy, Physical and Historical Geology. Honors: William P. Phillips Memorial Scholarship (West Chester University); National Air and Space Museum Certificate of Award 1983, 1986, 1989, 1991, 1992, 2002, 2004; American Geophysical Union Editor's Citation for Excellence in Refereeing - Journal Geophysical Research-Planets, 1992; Smithsonian Exhibition Award - Earth Today: A Digital View of Our Dynamic Planet, 1999; Certificate of Appreciation, Geological Society of America, 2005, 2006; Elected to Fellowship in the Geological Society of America, 2007. The Johns Hopkins University Applied Physics Laboratory 2009 Publication Award - Outstanding Research Paper, “Return to Mercury: A Global Perspective on MESSENGER’s First Mercury Flyby (S.C.
    [Show full text]
  • Mercury Friday, February 23
    ASTRONOMY 161 Introduction to Solar System Astronomy Class 18 Mercury Friday, February 23 Mercury: Basic characteristics Mass = 3.302×1023 kg (0.055 Earth) Radius = 2,440 km (0.383 Earth) Density = 5,427 kg/m³ Sidereal rotation period = 58.6462 d Albedo = 0.11 (Earth = 0.39) Average distance from Sun = 0.387 A.U. Mercury: Key Concepts (1) Mercury has a 3-to-2 spin-orbit coupling (not synchronous rotation). (2) Mercury has no permanent atmosphere because it is too hot. (3) Like the Moon, Mercury has cratered highlands and smooth plains. (4) Mercury has an extremely large iron-rich core. (1) Mercury has a 3-to-2 spin-orbit coupling (not synchronous rotation). Mercury is hard to observe from the Earth (because it is so close to the Sun). Its rotation speed can be found from Doppler shift of radar signals. Mercury’s unusual orbit Orbital period = 87.969 days Rotation period = 58.646 days = (2/3) x 87.969 days Mercury is NOT in synchronous rotation (1 rotation per orbit). Instead, it has 3-to-2 spin-orbit coupling (3 rotations for 2 orbits). Synchronous rotation (WRONG!) 3-to-2 spin-orbit coupling (RIGHT!) Time between one noon and the next is 176 days. Sun is above the horizon for 88 days at the time. Daytime temperatures reach as high as: 700 Kelvin (800 degrees F). Nighttime temperatures drops as low as: 100 Kelvin (-270 degrees F). (2) Mercury has no permanent atmosphere because it is too hot (and has low escape speed). Temperature is a measure of the 3kT v = random speed of m atoms (or v typical speed of atom molecules).
    [Show full text]
  • True Polar Wander of Mercury
    Mercury: Current and Future Science 2018 (LPI Contrib. No. 2047) 6098.pdf TRUE POLAR WANDER OF MERCURY. J. T. Keane1 and I. Matsuyama2; 1California Institute of Technology, Pasadena, CA 91125, USA ([email protected]); 2Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. Introduction: The spin of a planet is not constant to the Sun and subject to stronger tidal and rotational with time. Planetary spins evolve on a variety of time- forces. However, even with this corrected dynamical scales due to a variety of internal and external forces. oblateness, the required orbital configuration appears One process for changing the spin of a planet is true po- unreasonable−requiring semimajor axes <0.1 AU [5]. lar wander (TPW). TPW is the reorientation of the bulk An alternative explanation may be that a large fraction planet with respect to inertial space due to the redistri- of Mercury’s figure is a “thermal” figure, set Mercury’s bution of mass on or within the planet. The redistribu- close proximity to the Sun and its unique spin-orbit res- tion of mass alters the planet’s moments of inertia onance [7-8] (which are related to the planet’s spherical harmonic de- True Polar Wander of Mercury: While Mercury’s gree/order-2 gravity field). This process has been meas- impact basins and volcanic provinces cannot explain ured on the Earth, and inferred for a variety of solar sys- Mercury’s anomalous figure, they still have an im- tem bodies [1]. TPW can have significant consequences portant effect on planet’s moments of inertia and orien- for the climate, tectonics, and geophysics of a planet.
    [Show full text]
  • Mariner 10 Observations of Field-Aligned Currents at Mercury
    Planet. Space Sci., Vol. 45, No. 1, pp. 133-141, 1997 Pergamon #I? 1997 Published bv Elsevier Science Ltd P&ted in Great Brit& All rights reserved 0032-0633/97 $17.00+0.00 PII: S0032-0633(96)00104-3 Mariner 10 observations of field-aligned currents at Mercury J. A. Slavin,’ J. C. J. Owen,’ J. E. P. Connerney’ and S. P. Christon ‘Laboratory for Extraterrestrial Physics, NASA/GSFC, Greenbelt, MD 20771, U.S.A. ‘Astronomy Unit, Queen Mary and Westfield College, London, U.K. 3Department of Physics, University of Maryland, College Park, MD 20742, U.S.A. Received 5 October 1995; revised 11 April 1996; accepted 13 April 1996 magnetic field at Mercury with a dipole moment of about 300nT R& (see review by Connerney and Ness (1988)). This magnetic field is sufficient to stand-off the average solar wind at an altitude of about 1 RM as depicted in Fig. 1 (see review by Russell et al. (1988)). For the purposes of comparison the diameter of the Earth is indicated at the bottom of the figure (i.e. 1 RE = 6380 km ; 1 RM = 2439 km). Whether or not the solar wind is ever able to compress and/or erode the dayside magnetosphere to the point where solar wind ions could directly impact the surface remains a topic of considerable controversy (Siscoe and Christopher, 1975 ; Slavin and Holzer, 1979 ; Hood and Schubert, 1979; Suess and Goldstein, 1979; Goldstein et al., 1981). Overall, the basic morphology of this small mag- netosphere appears quite similar to that of the Earth.
    [Show full text]
  • The Geology of Mercury: Results from the First Two MESSENGER Flybys of the Innermost Planet
    The geology of Mercury: Results from the first two MESSENGER flybys of the innermost planet LOUISE M. PROCKTER1, SEAN C. SOLOMON2, JAMES W. HEAD3, THOMAS R. WATTERS4, SCOTT L. MURCHIE1, MARK S. ROBINSON5, CLARK R. CHAPMAN6, and RALPH McNUTT, JR1 1Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, U.S.A. 2Carnegie Institution of Washington, Washington, DC 20015, U.S.A. 3Brown University, Providence, RI 02912, U.S.A. 4National Air and Space Museum, Smithsonian Institution, Washington, DC 20560, U.S.A. 5Arizona State University, Tempe, AZ 85287, U.S.A. 6Southwest Research Institute, Boulder, CO 80302, U.S.A. In 2008 the MESSENGER spacecraft made two flybys of the planet Mercury, collecting a wealth of new near-global science data. These data included observations of approximately 50% of the planet that had not been viewed by the Mariner 10 spacecraft during its flybys in 1974-1975. Many of the new observations were focused on Mercury’s geology, including monochrome imaging at resolutions as high as 100 m/pixel, multispectral imaging in 11 filters at resolutions as high as 500 m/pixel, laser altimetry tracks extending over several thousands of kilometers, and high-resolution spectral measurements of several types of terrain. We present an overview of the first inferences on Mercury’s global geology from the MESSENGER observations. The new MESSENGER images and altimetry provide compelling evidence that volcanism was a widespread and protracted process on Mercury. MESSENGER observations show distinct spectral units as well as morphological evidence suggesting embayment and possibly pyroclastic eruptions. Preliminary measurements of impact crater size-frequency distributions suggest that plains material on Mercury’s surface ranges in age from a time shortly after the end of heavy impact bombardment to as young as perhaps 1 billion years ago.
    [Show full text]
  • 1 the Lifecycle of Hollows on Mercury
    The Lifecycle of Hollows on Mercury: An Evaluation of Candidate Volatile Phases and a Novel Model of Formation. 1 1 2 3 M. S. Phillips , J. E. Moersch , C. E. Viviano , J. P. Emery 1Department of Earth and Planetary Sciences, University of Tennessee, Knoxville 2Planetary Exploration Group, Johns Hopkins University Applied Physics Laboratory 3Department of Astronomy and Planetary Sciences, Northern Arizona University Corresponding author: Michael Phillips ([email protected]) Keywords: Mercury, hollows, thermal model, fumarole. Abstract On Mercury, high-reflectance, flat-floored depressions called hollows are observed nearly globally within low-reflectance material, one of Mercury’s major color units. Hollows are thought to be young, or even currently active, features that form via sublimation, or a “sublimation-like” process. The apparent abundance of sulfides within LRM combined with spectral detections of sulfides associated with hollows suggests that sulfides may be the phase responsible for hollow formation. Despite the association of sulfides with hollows, it is still not clear whether sulfides are the hollow-forming phase. To better understand which phase(s) might be responsible for hollow formation, we calculated sublimation rates for 57 candidate hollow-forming volatile phases from the surface of Mercury and as a function of depth beneath regolith lag deposits of various thicknesses. We found that stearic acid (C18H36O2), fullerenes (C60, C70), and elemental sulfur (S) have the appropriate thermophysical properties to explain hollow formation. Stearic acid and fullerenes are implausible hollow-forming phases because they are unlikely to have been delivered to or generated on Mercury in high enough volume to account for hollows.
    [Show full text]
  • The Planetary Geology Division of the Geological Society of America
    The Planetary Geology Division of the Geological Society of America Volume 27, Number 1 March 2009 Message from the Chair on the latest MESSENGER mission results from Mercury and an impact cratering session to honor this year’s Gilbert award winner, the Louise M. Prockter indefatigable Bob Strom. The abstract deadline Applied Physics Laboratory, for the annual meeting will be August 11, and Johns Hopkins University we encourage you to consider submitting a paper. Abstract submittals will begin in April, but you can view the topical sessions now at As this year’s Chair it is my turn to thank you http://www.geosociety.org/meetings/2009/sessi all for your continued support of our Division, ons/topical.asp. whether through your membership dues, service as a judge for the Dwornik student Student papers are especially welcome, and award, or supporting us at our booth during last their authors can apply for one of our new year’s GSA Annual Meeting in Houston. The student awards to help offset travel costs (after Houston meeting was well attended, and we the meeting registration opens, look for capitalized on the location and the ties to information on the PGD website at human exploration that abound there. The http://www.geosociety.org/meetings/2009/sessi Planetary Geology Division historically has a ons/topical.asp.) significant number of topical sessions at the annual meeting, and it is a great opportunity to Despite the current economic uncertainties, I mix with terrestrial geologists, many of whom am happy to be writing this at a time when we are fascinated by what we do.
    [Show full text]
  • Meet the Planets Table of Contents
    Teaching Activity Guide Meet the Planets Table of Contents 3 How to Use This Activity Guide 4 What Do Children Already Know? 4 Pre-Reading Questions 5 Thinking It Through & Writing Prompts 5 Comprehension Questions 6 Find in the Art 8 People of History in the Art 11 Vocabulary Game 11 Using the Words 12 Silly Sentence Structure Activity 13 Sequence Sentence Strips 15 Word Search 16 Solar System Cards 21 Rotation or Revolution? 22 Science Journal 24 True or False? 25 Which Planet? 26 Temperatures 27 Scale and Distance 30 Coloring Pages 33 Glossary 39 Answers 51 Appendix A—“What Children Know” Cards 52 Appendix B—Venn Diagram 53 Appendix C—Vocabulary Cards Copyright 2011 © Arbordale Publishing These activities may be copied for personal and non-commercial use in educational settings. www.ArbordalePublishing.com Arbordale Publishing formerly Sylvan Dell Publishing by John McGranaghan Mt. Pleasant, SC 29464 illustrated by Laurie Allen Klein How to Use This Activity Guide There are a wide variety of activities that teach or supplement all curricular areas. The activities are easily adapted up or down depending on the age and abilities of the children involved. And, it is easy to pick and choose what is appropriate for your setting and the time involved. Most activities can be done with an individual child or a group of children. Glossary/Vocabulary words: Words may be written on index cards, a poster board, or on a chalkboard for a “word wall.” If writing on poster board or chalkboard, you might want to sort words into nouns, verbs, etc.
    [Show full text]
  • Space Environment of Mercury at the Time of the First MESSENGER Flyby: Solar Wind and Interplanetary Magnetic Field Modeling of Upstream Conditions Daniel N
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, A10101, doi:10.1029/2009JA014287, 2009 Space environment of Mercury at the time of the first MESSENGER flyby: Solar wind and interplanetary magnetic field modeling of upstream conditions Daniel N. Baker,1 Dusan Odstrcil,2,3 Brian J. Anderson,4 C. Nick Arge,5 Mehdi Benna,6 George Gloeckler,7 Jim M. Raines,7 David Schriver,8 James A. Slavin,9 Sean C. Solomon,10 Rosemary M. Killen,11 and Thomas H. Zurbuchen7 Received 23 March 2009; revised 7 July 2009; accepted 20 July 2009; published 2 October 2009. [1] The first flyby of Mercury by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft occurred on 14 January 2008. In order to provide contextual information about the solar wind (SW) properties and the interplanetary magnetic field near the planet, we have used an empirical modeling technique combined with a numerical physics-based SW model. The Wang-Sheeley-Arge (WSA) method uses solar photospheric magnetic field observations (from Earth-based instruments) in order to estimate inner heliospheric conditions out to 21.5 solar radii from the Sun. This information is then used as input to the global numerical magnetohydrodynamic model, ENLIL, which calculates SW velocity, density, temperature, and magnetic field strength and polarity throughout the inner heliosphere. The present paper shows WSA-ENLIL conditions computed for the several week period encompassing the first flyby. This information is used in conjunction with MESSENGER magnetometer data (and the only limited available MESSENGER SW plasma data) to help understand the Mercury flyby results. The in situ spacecraft data, in turn, can also be used iteratively to improve the model accuracy for inner heliospheric ‘‘space weather’’ purposes.
    [Show full text]