Interactions of weakly or non-magnetized bodies with solar system plasmas [Elektronische Ressource] : Mars and the moons of Saturn / von Elias Roussos
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Interactions of weakly or non-magnetized bodies with solar system plasmas [Elektronische Ressource] : Mars and the moons of Saturn / von Elias Roussos

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189 Pages
English

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Interactionsofweaklyornon-magnetizedbodieswithsolarsystemplasmas: MarsandthemoonsofSaturnVonderFakultät fürElektrotechnik,Informationstechnik,PhysikderTechnischenUniversitätCarolo-WilhelminazuBraunschweigzurErlangungdesGradeseinesDoktorsderNaturwissenschaften(Dr.rer.nat.)genehmigteDissertationvonEliasRoussosausAthen,GriechenlandBibliografischeInformationDerDeutschenBibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in der DeutschenNationalbibliografie;detailliertebibliografischeDatensindimInternetüberhttp://dnb.ddb.deabrufbar.1. ReferentinoderReferent: Prof. Dr. Uwe Motschmann2. ReferentinoderReferent: Prof. Dr. JoachimSaureingereichtam: 28November2007mündlichePrüfung(Disputation)am: 6February2008ISBN978-3-936586-79-4CopernicusPublications2008http://publications.copernicus.orgc EliasRoussosPrintedinGermanyContentsSummary 111 Introduction 151.1 Marsinthesolarwind . . . . . . . . . . . . . . . . . . . . . . . . . . . 171.2 TheSaturnianmagnetosphere. . . . . . . . . . . . . . . . . . . . . . . . 211.3 Coldplasmaandenergeticparticles . . . . . . . . . . . . . . . . . . . . 242 Particlesandfieldsinstrumentation 272.1 ParticlesandfieldsinstrumentationonMarsExpress . . . . . . . . . . . 272.2 ParticlesandfieldsinstrumentationonCassini . . . . . . . . . . . . . . . 352.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 The interaction of Mars with the solar wind: Mars Express ASPERA-3 ob-servations 413.

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Published 01 January 2008
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Interactions of weakly or nonmagnetized bodies with solar system plasmas: Mars and the moons of Saturn
Von der Fakultät für Elektrotechnik, Informationstechnik, Physik der Technischen Universität CaroloWilhelmina zu Braunschweig zur Erlangung des Grades eines Doktors der Naturwissenschaften (Dr.rer.nat.) genehmigte Dissertation
von Elias Roussos aus Athen, Griechenland
Bibliografische Information Der Deutschen Bibliothek Die Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http://dnb.ddb.deabrufbar.
1. Referentin oder Referent: Prof. Dr. Uwe Motschmann 2. Referentin oder Referent: Prof. Dr. Joachim Saur eingereicht am: 28 November 2007 mündliche Prüfung (Disputation) am: 6 February 2008
ISBN 9783936586794
Copernicus Publications 2008 http://publications.copernicus.org Roussosc Elias
Printed in Germany
Contents
Summary
1
2
3
4
5
Introduction 1.1 Mars in the solar wind . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 The Saturnian magnetosphere . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Cold plasma and energetic particles . . . . . . . . . . . . . . . . . . . .
Particles and fields instrumentation 2.1 Particles and fields instrumentation on Mars Express . . . . . . . . . . . 2.2 Particles and fields instrumentation on Cassini . . . . . . . . . . . . . . . 2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
15 17 21 24
27 27 35 39
The interaction of Mars with the solar wind: Mars Express ASPERA3 ob servations 41 3.1 Coordinate systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.2 ASPERA3 data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3.3 Moment maps and heavy ion escape . . . . . . . . . . . . . . . . . . . . 47 3.4 Martian crustal magnetic field e55ects . . . . . . . . . . . . . . . . . . . . 3.5 Energetic electron asymmetries behind the terminator plane . . . . . . . . 61 3.6 Summary and outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Energetic particle absorption by Saturn’s icy moons: probes of magneto spheric dynamics and moon activity 67 4.1 The icy moons in Saturn’s inner magnetosphere . . . . . . . . . . . . . . 68 4.2 Energetic particle motion in Saturn’s radiation belts . . . . . . . . . . . . 69 4.3 Additional examples of electron microsignatures . . . . . . . . . . . . . 82 4.4 Statistical analysis of icy moon absorption signatures . . . . . . . . . . . 91 4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 4.6 Open questions and outlook . . . . . . . . . . . . . . . . . . . . . . . . . 109
Detection and physical characterization of rings and dust structures of the Saturnian system 111 5.1 Energetic electron absorption by asteroidsized moons . . . . . . . . . . 112 5.2 Electron absorption by Telesto and Helene . . . . . . . . . . . . . . . . . 113 5.3 Electron depletions at Methone’s distance . . . . . . . . . . . . . . . . . 118 5.4 The discovery of an arc in Saturn’s Gring . . . . . . . . . . . . . . . . . 127 5.5 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
3
Contents
6
7
A
Hybrid simulations of Saturn’s moon Rhea interaction with the magneto spheric plasma 133 6.1 Lunar type interactions at Saturn . . . . . . . . . . . . . . . . . . . . . . 133 6.2 Saturn’s moon Rhea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 6.3 The simulation code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 6.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 6.5 Summary and outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Concluding remarks
Motion of trapped particles in Saturn’s magnetosphere A.1 Symbols and constants . . . . . . . . . . . . . . . . . . . . . . . . . . . A.2 Useful expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A.3 Longitudinal drifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A.4 Keplerian motion and relative motion to charged particles . . . . . . . . . A.5 Bounce motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A.6 Gyration motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A.7 Applicability of formulas . . . . . . . . . . . . . . . . . . . . . . . . . .
Bibliography
Publications
Acknowledgements
Curriculum Vitae
4
161
163 163 164 165 165 166 167 167
169
181
187
189
List of Figures
1.1 1.2 1.3 1.4 1.5 1.6 1.7
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17
4.1 4.2
The main interaction regions of Martian induced magnetospheric cavity . The magnetic anomalies of Mars . . . . . . . . . . . . . . . . . . . . . . The Saturnian magnetosphere . . . . . . . . . . . . . . . . . . . . . . . . Energetic ions and electrons at Saturn’s inner magnetosphere . . . . . . . Kappa distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gradient drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gradient drift at Saturn . . . . . . . . . . . . . . . . . . . . . . . . . . .
The orbit of Mars Express . . . . . . . . . . . The IMA and ELS sensors . . . . . . . . . . . ELS cutsectional view . . . . . . . . . . . . . IMA cutsectional view . . . . . . . . . . . . . Maxwellian distributions and plasma moments The orbital tour for Cassini’s primary mission . The LEMMS sensor . . . . . . . . . . . . . . . LEMMS cutsectional view . . . . . . . . . . .
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MEX orbit in dierent coordinate systems . . . . . . . . . . . . . . . . . Typical ASPERA3 recordings . . . . . . . . . . . . . . . . . . . . . . . M/q vs E/q matrices for a typical MEX orbit . . . . . . . . . . . . . . . . Electron number density estimations . . . . . . . . . . . . . . . . . . . . Maximum electron number density map . . . . . . . . . . . . . . . . . . Electron temperature map . . . . . . . . . . . . . . . . . . . . . . . . . . Solar wind ion density map . . . . . . . . . . . . . . . . . . . . . . . . . ++ Vector velocity map of He ions . . . . . . . . . . . . . . . . . . . . . . Heavy ion flux in the MSE coordinate system . . . . . . . . . . . . . . . Total escape rate as a function of Xdistance . . . . . . . . . . . . . . . . ASPERA3 recordings after May 2007 . . . . . . . . . . . . . . . . . . . Magnetosheath fluxes overplayed on the map of Mars . . . . . . . . . . . Statistics on ELS data samples . . . . . . . . . . . . . . . . . . . . . . . Magnetosheath electron intrusion percentage, as a function of altitude . . Statistics of observations above regions of dierent crustal field strength . High flux event percentages in the MSE system . . . . . . . . . . . . . . High flux event percentages as a function of crustal field strength . . . . .
Moons and rings of Saturn . . . . . . . . . . . . . . . . . . . . . . . . . Sketch of charged particle motion in the Saturnian magnetosphere . . . .
18 20 22 23 25 26 26
28 29 29 30 34 35 36 37
42 43 46 48 49 50 51 52 53 54 56 58 59 60 61 62 64
69 70
5
List of Figures
6
4.3 4.4 4.5 4.6
4.7 4.8 4.9
4.10 4.11 4.12
4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27 4.28 4.29
5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14 5.15
Equatorial pitch angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Electron resonant energies as a function ofLandaeq. . . . . . . . . . . 73 LEMMS PHA channel electron data from a close Enceladus flyby . . . . 74 Relative contribution of penetrating radiation to the count rates of the C channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 MeV ion macrosignatures . . . . . . . . . . . . . . . . . . . . . . . . . . 77 Störmer orbits at the Earth . . . . . . . . . . . . . . . . . . . . . . . . . 79 Absolute value of half bounce azimuthal distance as a function of energy andL. . 80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energetic electron and ion moon encounter geometry . . . . . . . . . . . 81 Image of Tethys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Multiple microsignatures in the Cchannels during the Tethys Lshell cross ing on day 89 of 2005 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Double Tethys signature in the 2849 keV electrons on day 47 (2005) . . 86 Microsignature erosion by particle di89. . . . . . . . . . . . usion . . . . Enceladus microsignatures . . . . . . . . . . . . . . . . . . . . . . . . . 90 Lshell crossings statistics . . . . . . . . . . . . . . . . . . . . . . . . . 92 Mimas microsignatures on day 104 of 2005 . . . . . . . . . . . . . . . . 93 Fit to a Tethys microsignature profile . . . . . . . . . . . . . . . . . . . . 96 Variation ofDLLat Tethys, as a function ofaeq. . . . . . . . . . . . . . . 96 Ldependence of theDLLfor 2849 keV electrons 97. . . . . . . . . . . . . SOI count rate profiles for keV and MeV electrons . . . . . . . . . . . . 98 Simulated microsignature . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Simulated microsignature . . . . . . . . . . . . . . . . . . . . . . . . . . 100 A fit to a Mimas microsignature . . . . . . . . . . . . . . . . . . . . . . 101 Ldependence ofDLL. . . . . . . . . . . . . . 102for high energy electrons Displacement of Tethys’s Cchannel microsignatures vs local time . . . . 105 Displacement of Dione’s Cchannel microsignatures vs local time . . . . 105 The geometry of microsignature detection for nonaxisymmetric drift shells107 A Tethys microsignature . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Absorption escape possibilities from small moons . . . . . . . . . . . . Erkas a function ofaeqand the eective absorption regions for electrons Telesto flyby geometry . . . . . . . . . . . . . . . . . . . . . . . . . . The Telesto microsignature . . . . . . . . . . . . . . . . . . . . . . . . The Helene flyby geometry . . . . . . . . . . . . . . . . . . . . . . . . The Helene microsignature . . . . . . . . . . . . . . . . . . . . . . . . The Methone flyby geometry . . . . . . . . . . . . . . . . . . . . . . . Electron depletions around Methone’s orbit . . . . . . . . . . . . . . . The optical depth of Methone’s arc . . . . . . . . . . . . . . . . . . . . Prometheus disturbing the Fring . . . . . . . . . . . . . . . . . . . . . The 60th moon of Saturn . . . . . . . . . . . . . . . . . . . . . . . . . The Gring ion macrosignature in LEMMS data . . . . . . . . . . . . . Saturn’s F and E rings . . . . . . . . . . . . . . . . . . . . . . . . . . Gring arc images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gring arc optical depth profile . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . .
113 114 115 116 117 118 120 121 123 125 127 128 129 129 130
6.1 6.2 6.3 6.4 6.5
6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15
A.1
List of Figures
Images of Rhea from Cassini . . . . . . . . . . . . . . . . . . . . . . . . Overview of the simulation results for the “ideal case” run . . . . . . . . Illustration of Equations 6.7 . . . . . . . . . . . . . . . . . . . . . . . . Comparison of Equation 6.7 solutions with the simulated data . . . . . . The asymmetric shape of Rhea’s density wake parallel and perpendicular to the magnetic field lines . . . . . . . . . . . . . . . . . . . . . . . . . . Magnetic field perturbations in a the yzplane, just behind Rhea . . . . . . Magnetic field perturbations in a the xzplane downstream of Rhea . . . . Perturbations ofvyandvzin an yzcut just behind Rhea . . . . . . . . . . Perturbations ofvxandvzin an yzcut just behind Rhea . . . . . . . . . . Comparison of Equation 6.10 solution with the simulated data . . . . . . Velocity and electric field in the plasma rest frame in the wake of Rhea . . Comparison of simulation results with Cassini magnetometer data . . . . Density and velocity of escaping heavy ions from Rhea . . . . . . . . . . Synthetic spectrogram for the Rhea flyby trajectory . . . . . . . . . . . . Phasespace plot ofVzalong a trajectory parallel to the xaxis . . . . . . .
135 141 143 144
146 148 149 150 151 151 153 154 156 157 158
Reference values for charged particle motion scales at Saturn . . . . . . . 168
7
List of Tables
2.1
4.1 4.2 4.3
5.1
5.2
6.1
6.2
List of LEMMS electron channels and their energy ranges . . . . . . . . 38
List of Saturn’s large icy moons . . . . . . . . . . . . . . . . . . . . . . Tethys microsignatures in the first seven orbits of Cassini . . . . . . . . . Analysis of Mimas microsignatures . . . . . . . . . . . . . . . . . . . .
70 85 94
List of several physical and orbital parameters for Telesto, Helene and Methone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Summary of the observed microsignatures from small moons . . . . . . . 119
Values and ranges of the various parameters describing Rhea’s space en vironment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 List of parameters used for the two simulation runs. . . . . . . . . . . . . 139
9
Summary
The interaction of weakly or nonmagnetized planets and moons with the solar wind as well as with a magnetospheric plasma have been studied at Mars and the moons of Saturn using plasma data from the ASPERA3 instrument onboard Mars Express and energetic charged particle measurements at the moons of Saturn from the MIMI/LEMMS instru ment aboard Cassini, respectively. The analysis of data recorded for Saturn’s moons was complemented by hybrid plasma simulations. A series of results have been obtained from the study of each individual system: (a) Using plasma data from the ASPERA3 instrument onboard Mars Express, plasma fluid parameters (moments) have been extracted using two standard methods: by inte gration of the particle flux over the instruments energy range and by fitting the phase space density profiles to maxwellian distributions. The estimated moment values from two ASPERA3 sensors were evaluated by comparing them with the expected values for the solar wind and the various interaction regions within the martian magnetospheric cav ity. This comparison helped to identify the best calculation method and the limitations of each sensor. Following these steps, plasma moment maps that describe the interaction of Mars with the solar wind have been constructed for the first time and an estimation of the planet’s atmospheric erosion rates has been performed. (b) Using data on nonionospheric electrons from the ELS sensor of ASPERA3 on board Mars Express, the influence of two dierent factors that can control the global configuration of the Martian magnetosphere has been investigated. These two factors are the direction that the solar wind convective electric field,ES W, is pointing and the loca tion and intensity of the crustal magnetic field sources of the planet. Information on the pointing of the solar wind convective electric field was extracted by the magnetometer observations of Mars Global Surveyor (MGS), which was operating in parallel with Mars Express in orbit around Mars. Crustal magnetic field data were retrieved from standard ized maps that were originally constructed from MGS observations. The nonionospheric electron data were organized in dierent coordinate systems based on theES Wpointing and on the crustal field intensity. Interesting asymmetries were found for magnetosheath electrons, during extreme cases (high flux events). More specifically, it was found that high fluxes of magnetosheath electrons, measured at the terminator of the planet can in trude towards the wake under certain, combined geometries involving the planet’s crustal field locations and the pointing of theES Winfluence of the crustal fields on the in. The trusion of magnetosheath electrons at low altitudes on the planet’s dayside, has also been evaluated. (c) Within 9Rsfrom the center of Saturn (1Rs=60268 km) seven moons with a diam eter greater than 100 km are orbiting the planet in almost circular and equatorial orbits. These moons interact continuously with the trapped plasma of radiation belts. Many of
11