Table Of ContentThe Plasma Environment of Venus, Mars, and Titan
Space Sciences Series of ISSI
Volume 37
Forfurthervolumes:
www.springer.com/series/6592
Karoly Szego
Editor
The Plasma Environment
of Venus, Mars, and Titan
Previously published in Space Science Reviews Volume 162,
Issues 1–4, 2011
Editor
KarolySzego
KFKIResearchInstituteforParticleandNuclearPhysics
KonkolyThegeStreet29-33
1121Budapest
Hungary
ISSN1385-7525 SpaceSciencesSeriesofISSI
ISBN978-1-4614-3289-0
SpringerNewYorkDordrechtHeidelbergLondon
LibraryofCongressControlNumber:2012930942
©SpringerScience+BusinessMedia,LLC2012
Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewrittenper-
missionofthepublisher(SpringerScience+BusinessMedia,LLC,233SpringStreet,NewYork,NY10013,
USA),exceptforbriefexcerptsinconnectionwithreviewsorscholarlyanalysis.Useinconnectionwithany
formofinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar
methodologynowknownorhereafterdevelopedisforbidden.
Theuseinthispublicationoftradenames,trademarks,servicemarks,andsimilarterms,eveniftheyare
notidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyaresubjectto
proprietaryrights.
Printedonacid-freepaper
SpringerispartofSpringerScience+BusinessMedia(www.springer.com)
Contents
ThePlasmaEnvironmentofVenus,Mars,andTitan,anIntroduction
(cid:2) (cid:2)
K.Szego A.-M.Harri M.Blanc 1
UpstreamIonCyclotronWavesatVenusandMars
(cid:2) (cid:2)
M.Delva C.Mazelle C.Bertucci 5
UpstreamofSaturnandTitan
(cid:2) (cid:2) (cid:2) (cid:2) (cid:2) (cid:2)
C.S.Arridge N.André C.L.Bertucci P.Garnier C.M.Jackman Z.Németh
(cid:2) (cid:2) (cid:2) (cid:2)
A.M.Rymer N.Sergis K.Szego A.J.Coates F.J.Crary 25
RecentResultsfromTitan’sIonosphere
(cid:2) (cid:2) (cid:2) (cid:2) (cid:2) (cid:2)
A.J.Coates J.-E.Wahlund K.Ågren N.Edberg J.Cui A.Wellbrock
K.Szego 85
TheInducedMagnetospheresofMars,Venus,andTitan
(cid:2) (cid:2) (cid:2) (cid:2) (cid:2) (cid:2)
C.Bertucci F.Duru N.Edberg M.Fraenz C.Martinecz K.Szego
O.Vaisberg 113
IonEnergizationandEscapeonMarsandVenus
(cid:2) (cid:2) (cid:2) (cid:2) (cid:2) (cid:2)
E.Dubinin M.Fraenz A.Fedorov R.Lundin N.Edberg F.Duru
O.Vaisberg 173
ExospheresandEnergeticNeutralAtomsofMars,VenusandTitan
(cid:2) (cid:2) (cid:2) (cid:2) (cid:2) (cid:2)
Y.Futaana J.-Y.Chaufray H.T.Smith P.Garnier H.Lichtenegger M.Delva
(cid:2)
H.Gröller A.Mura 213
ModelingofVenus,Mars,andTitan
(cid:2) (cid:2) (cid:2) (cid:2)
E.Kallio J.-Y.Chaufray R.Modolo D.Snowden R.Winglee 267
IonAccelerationandOutflowfromMarsandVenus:AnOverview
R.Lundin 309
SpaceSciRev(2011)162:1–4
DOI10.1007/s11214-011-9844-2
The Plasma Environment of Venus, Mars, and Titan,
an Introduction
KarolySzego·Ari-MattiHarri·MichelBlanc
Publishedonline:1November2011
©SpringerScience+BusinessMediaB.V.2011
InDecember2009theEUROPLANETResearchInfrastructure,aprojectfundedbytheEu-
ropeanCommunityundertheCapacitiesprogrammeoftheSeventhFrameworkProgramme
(grantagreementnumber228319)andtheInternationalSpaceScienceInstitute,organized
aworkshopinBerntooverviewandsummarizeourcurrentknowledgeontheplasmaenvi-
ronmentsofVenus,Mars,andTitan.Thiswasthefirstworkshoporganizedintheseriesof
fourplannedinthenetworkingactivityNA-2ofEuroplanetRI.Emphasiswasonnewre-
sults,sincemanyexcellentreviewswerepublishedrecently.Thecomparisonoftheplasma
environmentofthesethreesolarsystemobjectswasaprimaryfocusoftheworkshop,which
alsoaimedatdefiningdirectionsforfutureresearch,throughfurtheruseofexistingdataor
developmentofnewspacemissions.
In this introductory paper, we summarize the main results of this workshop, via an
overviewofthedifferentchaptersitcontains.
Unlike the Earth, our neighbours Venus and Mars have no global magnetic fields, al-
thoughMarshassmall-scalecrustalfields;andTitan,toourbestknowledge,isalsoanon-
magneticbody.Thesethreeobjectsaretheonlynon-magneticsolarsystembodieshaving
a dense atmosphere. Venus and Mars have the supersonic and super-Alfvenic solar wind
astheirplasmaenvironment.Titan,incontrast,islocatedinsideSaturn’shot,rapidlyrotat-
ing,subsonic,multicomponentmagnetosphericflow(althoughitoccasionallymakesexcur-
sionsintothemagnetosheath)anditsenvironmentishighlyvariableintime.Accordingly,
(cid:2)
K.Szego( )
KFKIResearchInstituteforParticleandNuclearResearch,Budapest,Hungary
e-mail:[email protected]
A.-M.Harri
FinnishMeteorologicalInstitute,Helsinki,Finnland
M.Blanc
EcolePolytechnique,PalaiseauandIRAP,Toulouse,France
M.Blanc
InternationalSpaceScienceInstitute,Bern,Switzerland
1 Reprintedfromthejournal
K.Szegoetal.
these objects provide a wide parameter range for the investigations of the interaction of
non-magnetized objects with their plasma environments. It is remarkable that their global
structureisverysimilar,evenifeachobstaclehasitsowncharacteristicsdependingonthe
actualplasmaregime.
Inthelastfewyears,Europeanandinternationalspacecrafthavegatheredsignificantnew
data on the interaction of these non-magnetized objects with their plasma environments.
Cassini-Huygens1 has accumulated data over 70 flybys of Titan; Mars Express2 has over
sevenyearsofdatafromMars,andVenusExpress3 over4yearsofdatafromVenus.This
databonanzawillcontinuetoaccumulateduringtheextendedphaseofallofthesemissions,
providinganidealobservationalsupporttosummarize,compareandanalysethesimilarities
and differences of their plasma interaction. Cometary interaction with the solar wind also
bearssimilaritieswiththeseobjects;thereforetheknowledgepresentedinthisvolumewill
behighlyusefulfortheROSETTAcometchaser(amissionoftheEuropeanSpaceAgency)
examiningatclosedistancehowafrozencometistransformedbytheheatoftheSuninthe
solarwind.
Thebasicprocessesofspaceplasmaphysicshavebeenestablishedbythescientificinves-
tigationsduringthepastfewdecades.Currentlytheresearchisfocusedontheunderstanding
oftheevolutionofplanetaryatmospheresanditseffectontheclimateevolutionovergeo-
logicaltimescales.Thatrequiresthestudyoftheflowofenergyandmomentumfromthe
solar wind through the different planetary plasma regions leading to the loss of planetary
material;mutatismutandis,thesameholdsforTitan.
Around non-magnetic solar system bodies the interaction of flowing plasma with an
ionised obstacle creates a layered, onion-like structure in the plasma flow in front of the
obstacle, and an elongated plasma formation behind it for typical interplanetary magnetic
field (IMF) configurations. In front of the obstacle the magnetic field piles up forming a
magneticbarrier.Themagneticfieldconfigurationbehindtheobstacle,inthetail,depends
on the dynamic pressure of the flow. Recent investigations have revealed that when the
IMF is parallel to the flow, a more complex plasma structure is generated around the ob-
stacle, and the magnetic barrier is missing. The features of the interaction, including the
nature and the features of the boundary layers, can be very different, depending upon the
propertiesoftheincidentplasmaandthenatureoftheobstacle.Aparticularroleisplayed
by the pickup processes. The pickup ion radius depends on the strength of the magnetic
field which e.g. in thecaseof Titan is of thesameorder as theobstacle radius.The outer
limit of the spatial volume which is under the control of ions originating from the obsta-
cle is the boundary of the induced magnetosphere. The boundaries around the obstacles
are of finite width. This is particularly important for the cometary bow shock, its consid-
erable width allows neutrals to be ionized within the bow shock resulting in a new cate-
gory of shocks, the mass loaded shock. The mass loading region is particularly extended
around Titan, its width is a few Titan radii. As a consequence, the magnetic field and the
pickup velocity are continuously changing in this region. For the non-magnetized planets
the induced magnetosphere is not axially symmetric, due to the electric field induced by
themagneticfieldandflowvelocity;thisintroducesasymmetryalsointhestructureofthe
tail.
1TheCassini-HuygensspacemissionisaninternationalcooperativeeffortofNASA,theEuropeanSpace
Agency(ESA),theItalianSpaceAgency(ASI)andseveralseparateEuropeanacademicandindustrialcon-
tributors.
2TheMarsExpressspacemissionisacooperativeeffortoftheEuropeanSpaceAgency.
3TheVenusExpressspacemissionisacooperativeeffortoftheEuropeanSpaceAgency.
Reprintedfromthejournal 2
ThePlasmaEnvironmentofVenus,Mars,andTitan,anIntroduction
Thephysicalprocessesevidentlyinvolveelectrons,whichbydefinitionaccountforhalf
of the plasma population (except when multiply-charged ions are present). The electrons
comefromsourcesincludingtheincomingplasmaflowandtheionizationprocesses(photo
ionizationandimpactionization)intheionosphereoftheobject;theymayalsobeproduced
intheregionoftheobjectbyadditionalprocesses.Theionospheresareproducedbysolar
radiationandprecipitatingelectronimpact(fromthemagnetosphereorshockedsolarwind),
or a combination of both. Electrons in the environment near non-magnetized objects can
provideasourceofenergyfortheatmosphere.
Thepapersofthisvolumedescribefirsttheupstreamconditions,thentheobstacles,the
formationoftheinducedmagnetospheres,ionaccelerationandoutflow;thespecialfeatures
derivedfromtheobservationsofenergeticneutrals,andapaperonmodellingcomplement
thedescription.Letussayafewwordsabouteachofthem.
The paper by Delva et al. reviews the proton upstream waves reported for Venus and
Mars,theirgenerationmechanismandconsequencesfortheplanetaryexospheres.Arridge
et al. discuss the upstream parameters controlling the interaction of Titan and its effects
on the chemistry of the ionosphere. The physics of Saturn’s magnetosphere near Titan
is also considered in this respect resulting in the high variability of the plasma environ-
ment. Titan has the most significant atmosphere of any moon in the solar system. The
paper of Coates et al. reviews several recent advances in our description and understand-
ing of Titan’s ionosphere, and compares it to the ionospheres of Venus and Mars. The
role of ionospheric photoelectrons is also considered. Dubinin et al. focus on the differ-
ent channels through which planetary matter escapes. Forces responsible for energization
in the various channels are special. The solar wind forcing of ion escape for Venus and
Mars is the focal topic of the review paper of Lundin. The aim of this overview is to
analyse the different acceleration processes associated with ion outflow. A broad descrip-
tion of the structure and properties of the induced magnetospheres and the boundaries
of Venus, Mars an Titan is presented by Bertucci et al. The concept of fossil magnetic
fields is also analyzed in depth. Analysis of energetic neutrals brings important informa-
tionabouttheplasmaenvironmentsandabouttheneutralexospheres;thisnoveltechnique
is presented by Yoshifumi et al. Numerical modeling of the global plasma and neutral
dynamics at Venus, Mars and Titan, presented by Kallio et al., makes this volume com-
plete.
Afocalproblemofthecurrentresearchistoclarifytheoutflowchannelsoftheplanetary
plasmaandtheplanetaryplasmalossasaresultoftheinteractionwiththeimpingingplasma
flow.Apartoftheoutflowtakesplacethroughthetailregion;anotherpartescapesthrough
theboundarylayeroftheinducedmagnetosphere.Thedriveroftheoutflowisdifferentin
thedifferentchannels,thisisalsotobeclarifiedinthefuture.Thesophisticatedinstrumen-
tation e.g. onboard of Mars-Express and Venus-Express makes it possible to measure the
tailescapevelocities.Presentlythescientificcommunityisdebatingonhowtheionospheric
outflowismadepossible,andwhatistheroleofthermalescaperelativetothenon-thermal
escape processes. This requires the categorisation of the ionospheric structure, dynamics
andchemistry.Outflowintheboundariesrequirestheidentificationoftheboundariesandof
theroleofthedifferentfrictionaleffects,andtheprocessesthemselvesthatformthebound-
aryregionsandthetail.Additionalworkisnecessarytoquantifythepickupprocessesand
associatedwaveexcitations.
Insummary,thisvolumegathersinacomprehensiveandsystematicwayacomparison
of the different features of the similarities and differences in the plasma interactions of
Venus,MarsandTitan.Fromthiscomparison,onecanexploreasignificantfractionofthe
parameterspaceofmagnetizedplasmaflowinteractionswithnonmagnetizedobjectswith
3 Reprintedfromthejournal
K.Szegoetal.
anatmosphere.BeyondtheparticularcasesofVenus,MarsandTitan,thiscomparisonpartly
addresses the comet-solar wind interaction, and the interaction of some of the exoplanets
withtheirstellarwind.
Acknowledgements Theeditorsherethankalltherefereeswhoreviewedthearticlesinthisvolumefor
theirdedicationtothiswork.Theircontributionverymuchenhancedthevalueofthisvolume.
Reprintedfromthejournal 4
SpaceSciRev(2011)162:5–24
DOI10.1007/s11214-011-9828-2
Upstream Ion Cyclotron Waves at Venus and Mars
MagdaDelva·ChristianMazelle·CésarBertucci
Received:10February2011/Accepted:29August2011/Publishedonline:14October2011
©SpringerScience+BusinessMediaB.V.2011
Abstract The occurrence of waves generated by pick-up of planetary neutrals by the so-
lar wind around unmagnetized planets is an important indicator for the composition and
evolutionofplanetaryatmospheres.ForVenusandMars,long-termobservationsoftheup-
streammagneticfieldarenowavailableandprotoncyclotronwaveshavebeenreportedby
severalspacecraft.Observationsoftheseleft-handpolarizedwavesatthelocalprotoncy-
clotronfrequencyinthespacecraftframearereviewedfortheirspecificproperties,genera-
tionmechanismsandconsequencesfortheplanetaryexosphere.Comparisonofthereported
observationsleadstoasimilargeneralwaveoccurrenceatbothplanets,atcomparableloca-
tionswithrespecttotheplanet.However,thewavesatMarsareobservedmorefrequently
andforlongdurationsofseveralhours;thecyclotronwavepropertiesaremorepronounced,
withlargeramplitudes,strongerleft-handpolarizationandhighercoherencethanatVenus.
The geometrical configuration of the interplanetary magnetic field with respect to the so-
lar wind velocity and the relative density of upstream pick-up protons to the background
plasma are important parameters for wave generation. At Venus, where the relative exo-
sphericpick-upiondensityislow,wavegenerationwasfoundtomainlytakeplaceunder
stableandquasi-parallelconditionsofthemagneticfieldandthesolarwindvelocity.This
isinagreementwiththeory,whichpredictsfastwavegrowthfromtheion/ionbeaminsta-
bilityunderquasi-parallelconditionsalreadyforlowrelativepick-upiondensity.AtMars,
wheretherelativeexosphericpick-upiondensityishigher,upstreamwavegenerationmay
alsotakeplaceunderstableconditionswhenthesolarwindvelocityandmagneticfieldare
quasi-perpendicular.Atbothplanets,thealtitudeswhereupstreamprotoncyclotronwaves
wereobserved(8Venusand11Marsradii)arecomparableintermsofthebowshocknose
(cid:2)
M.Delva( )
SpaceResearchInstitute,AustrianAcademyofSciences,Schmiedlstrasse6,8042Graz,Austria
e-mail:[email protected]
url:http://www.iwf.oeaw.ac.at
C.Mazelle
CESR/UPS-CNRS,Toulouse,France
C.Bertucci
InstituteforAstronomyandSpacePhysics,IAFE,BuenosAires,Argentina
5 Reprintedfromthejournal
