20June2016
NeutralCloudTheory:
ModelsofPhysicalChemistryoftheIoPlasmaTorus
*Keypapers
GB=ground-based,DES=DonE.Shemansky,Fehot=fractionofhotelectrons,Thot=temperatureofhotelectrons
SI=SSII=S+SIII=S++SIV=S+++SV=S4+OI=OOII=O+OIII=O++OIV=O+++OV=O4+
NL2=NL2=fluxtubecontent
COREQ=COllisionalandRadiativeEQuilibrium
CITEP=ColoradoIoTorusEmissionsPackage
CHIANTI=http://www.chiantidatabase.org
CHEX=chargeexchange
1980–purplecoloreddatemeansalsoincludedunderUVemissionsbibliography
1992–greencoloreddatemeansalsoincludedunderTorusVariabilitybibliography
Date Paper
Atomic Results
Database
1982 Shemansky,Sandel,Theinjectionof
Te~constantfor0.5yrwithshort-termvariations.
energyintotheIoplasmatorus,J.
SystemIIIvariationsinTe.EnergybalanceusingprimarilySIII685A
Geophys.Res.,87,219-229
TehotterLT=22:30duskvs10:30dawn
e-heating:ioncollisionalheatingtooslow(6-10d).
Fehot<1%(Scudder1981,Shemansky1980)
1982 Brown,Shemansky,Onthenatureof
SIIemissionfromJupiter’shot
plasmatorus,Ap.J.,263,433-442
DES
1982 *Johnson,Strobel,Chargeexchange
intheIotorusandexosphere,J.
Geophys.Res.,87,10,385-10,393
SIIemissionlinesfromEUVtovisibleindicateTe~6.7eV–andSIIminor
iontoSIII>5.9RJ(v.differenttoinnercoldtorus).
FluctuationsinSIIassumedtobeduetovariationsinTe.
Ionizationtheorysuggestselectronsnotsolecontrolofionizationstate–
hintsatCHEX
CHEX–25reactionscalculated.
Forsimplemodelofneutrals(Smyth),ne,Te->composition&rates.No
radialtransport.
1
1983 Brown,Shemansky,Johnson,A
deficiencyofOIIIintheIoplasma
torus,Ap.J.,264,309-323
1983 Smyth,Shemansky,Escapeand
ionizationofatomicoxygenfrom
Io,Ap.J.,271,865-875
1983 Brown,Pilcher,Strobel,
Spectrophotometricstudiesofthe
Iotorus,PhysicsoftheJovian
Magnetosphere,Dessler(ed),CUP
1985 Linker,Kivelson,Moreno,Walker,
Explanationoftheinward
displacementofIo’shotplasma
torusandconsequencesfor
sputteringsources,Nature,315,
375-378
1985 *Smith,Strobel,Energypartitioning
intheIoplasmatorus,J.Geophys.
Res.,90,9469-9493
1985 Moreno,Newman,Kivelson,Ion
partitioninginthehotIotorus:
InfluenceofS2outgassing,J.
Geophys.Res.,90,12065-16072
DES& LackofdetectionofOIII5007A–previousdata/modelsshowO+/O++
Johnson
variesfrom100to2.4
JohnsonproposesCHEX-willremoveO++ions
Shemanskypresentsmodelofchemistryw/diffusionbutnoCHEX,whichis
discussedmoreasasourceofneutrals
UsesOIdetectionbyBrown1981(6300)plustorusmodeltoproducea
modeloftheneutralcloudofOaroundIo’sorbit.
AddsassumedsimilarScloud.Massandpowersourcetoolowfortorus,
evenwithlongdiffusiontimescales.
Noionchemistry–justelectrontemperatureanddensity.
NoCHEXinmodelbutrecognizespotentialimportance.
various Summaryofobservationsandmodelstodate.
Usefulreferenceforspectrallinesandemissionprocesses.
AimtoexplainpeakofNL2profileinwardofIo’sorbit.Neutralcloud
generatedbyejectionofneutralsfromIo’sequatoratspeeds>escape.
Assumeselectron-impactionizationwithlifetimesof~40hours.
PrefersS2+productionbecauseeasilylostviadissociativerecombination.
AssumesuniformNeandTe–probablymajorissue.
Needsspikeinf(v)ofescapingneutralstoconfinepeakto5.7RJ.
Strobel Modelwitheverything!Startsfromf(v)forpick-upionsandevolves
velocitydistribution.Assumesne=2000
NRL
Johnson Includesionization,CHEX,radiation,radialtransport.
Variables:tau,Q,Te
neutraldensity:no~22cm-3only,ns~0.1no,ns~2no
DrivenbyO+~660cm-3andO++<5cm-3
Johnson&
Strobel,
Brown83,
DES
AimtoaddresslowO++densitywithS2ratherthanSO2source.
Modelnotwellexplainedbutseemsa0-D(cubic-cm)model
Ionization,CHEX,radiation
Variables:Fehot(1keV),Q,tau,Ti->steadystate
DerivesS2~60%SO2,Fehot~0.05%,tau~35days
2
1986 Moreno,Barbosa,Massandenergy
balanceinthecoldIotorus,J.
Geophys.Res.,91,8993-8997
1987 Shemansky,Ratioofoxygento
sulfurintheIoplasmatorus,J.
Geophys.Res.,92,6141-6146
1987 Strobel,Energetics,luminosity,and
spectroscopyofIo’storus,in
Time-VariablePhenomenainthe
JovianSystem,Belton,West,Rahe
(eds)NASASP-494
1988 *Barbosa,Moreno,Acomprehensive
modelofiondiffusionandcharge
exchangeinthecoldIotorus,J.
Geophys.Res.,93,823-836
DES
Coldtorus.
Modelnotwellexplainedbutseemsa0-D(cubic-cm)model
Ionization,CHEX,radiation,tau~140-710days
Includes2-steprecombinationthatremovesoxygen:
O++SO2->O(fast)+SO2+thenSO2++e-->O(fast)+SO(fast)
V1/V2comparison.Model+data–Collisionaldiffusiveequilibrium.
O:S~equal.OII,SII,SIII–plusGBOI,SI–Skinner&Durrance1986
Bigchangesin833/834collisionstrengths.OII/OIIIdependenceonTe.
ArguesforS(O)/S(S)~4.IncludesCHEX–whichremovesO++
Summaryofstudiestodate–emphasizingtheenergetics.
Tableofcompositionshowingvariationsasinterpretationofemissions
changedfromVoyagerUVSonwardstoShemansky1987.
Innercoldtorus.Comprehensivemodelisrightphrase–includeselectron
collisions,radiativelosses,CHEX,radialtransportanddiffusive
equilibriumforlatitudinalstructure.
ConcludesSO2canprovideallneutrals,whenmolecularreactionsincluded
S+(220)S++(340),S+++(40),O+(800)O++(90)forhottorus.
(wouldbegreattore-dowithproperneutralkinetics&chemistryand
modernatomicdata)
3
1988 *Shemansky,Energybranchingin
theIoplasmatorus:Thefailureof
neutralcloudtheory,J.Geophys.
Res.,93,1773-1784
DES
1988 Smith,Bagenal,Cheng,Strobel,On
theenergycrisisintheIoplasma
torus,Geophys.Res.Lett.,15,546548
1989 *McGrath,Johnson,Charge
ExchangecrosssectionsfortheIo
plasmatorus,J.Geophys.Res.,94,
2677-26-83
1990 Shemansky,Criticalquantitiesfor
solarsystemscienceinatomic
andmolecularreactions,AIP
conferenceproceedings,206,163
Strobel
Tomatchionicstateswithrealistic(longer)timescalesadditionalenergyis
neededoverionpick-up
Smith&Strobel1985pointedouthotelectrons–butDESarguesthey
underestimatedradiativelosses
Assumesmaxwellians(arguesthatmacroscopicOK)
NotesthatCHEXrateshaveenergydependence
NotesthatSIIradiativecoefficienthasincreasedsignificantly
KeyparameterisSII/SIII–statesobservations<1,NCTgives10-20
dependingontau
Alsoaddresses“Pilcher&Morgancase”ofNe~104v.hardtodo.
ConcludesthatadditionalenergyeitherhastocomefromCHEXandPU
nearIo–OR–hote-(exceptSittler&Stobelputlimits)
Notes–CHEXcanremoveO,composimilartoSmith&Stobelexceptfor
amountofOIII
Fig1–Radiativecoolingcoefficients“Detailsofthesecalculationswillbe
publishedatalaterdate”
“Theseresultsarebasedonthelatestavailablecollisionstrengthand
electronicstructuredata.Detailswillbegiveninalaterpublications”–
noref.
Proposedinwardly-diffusingenergeticionssuppliedtheadditionalenergy
tothetorus.
N(S)~6,N(O)~30,Ne~2000cm-3
30CHEXreactioncross-sectionscalculatedvs.ionenergy.
FortorusquotesionizationBrown,Shemansky,CHEXJohnson1990,
McGrath&Johnson1989.
Arguesthatenhancedrecombinationratesmaybeneededtoexplainlow
abundanceofSII
4
1995 Matheson,Shemansky,Chemistry
andtransportintheIotorus
ramp,Icarus,submitted
COREQ
RadialmodeloftoruschemistryTefixedtoSittlerprofile.Exploredeffects
ofrateofradialtransport.Slow(60d)closeto6RJ,moderate(20d)
moderatebetterat7.2RJ.
Composition–ni/Ne
6RJ-S+(0.13)S++(0.18),S+++(0.02),O+(0.42)O++(0.015)
7.75RJ-S+(0.13)S++(0.09),S+++(0.02),O+(0.26)O++(0.22)
1996 Herbert,Asimpletransportmodel
fortheIoplasmatorus“ribbon”,
Geophys.Res.Lett.,23,2875-2878
LocationofRibbonmodeledwithradialtransportandpressuregradients.
UsesNL2profiletoderiveDLL.
Seemstocompletelyignoreroleofneutralcloud.
1998 Smyth,Marconi,Anexplanationfor
theeast-westasymmetryoftheIo
plasmatorus,J.Geophys.Res.,103,
9091-9100
2003 *Delamere,Bagenal,Modeling
variabilityofplasmaconditionsin
theIotorus,J.Geophys.Res.,108,
1276
ModelsS+,S++emissions–Dawn-duskasymmetry
Usestransport+Edawn-dusk+SIII+OTD+Io’sorbit.
Tau~25dat7RJ
2003 Smyth,Marconi,Natureofthe
iogenicplasmasourceinJupiter’s
magnetosphere.I.
Circumplanetarydistribution,
Icarus,166,85-106
2004 Hill,Dessler,Longitudinalvariation
ofiontemperatureintheIo
plasmatorus,J.Geophys.Res.,109,
A04206
CHIANTI 0-Dcm3model.Solveforsteady-stateflowofmassandenergy.
Emissionratesvs.TefromCHIANTI
Ionization–factorx2inS->S+intheliterature
RecombinatinofromLichtenberg&Thomas2001
SensitivitytoFehot,Tehot,O/S,SN,tau
V1,V2,Cassini
Ioneutralsource–S,O~0.5km/s
3-DneutralcloudmodelshapedbyionizationandCHEX
SystemIIIlongitudevariationsinTi(perp20-45eV,par10-30eV)from
Brown1995,Thomas2001,Schneider1997
UsesVIT4toderivePedersonconductanceforN,Sandarguespick-up
energycontrolledbyionosphericconductance(SigN+SigS)2
5
2004 Thomas,Bagenal,Hill,Wilson,The
Ioneutralcloudsandplasma
torus,inJupiter,Bagenal,
Dowling,McKinnon(eds),CUP
2004 Delamere,Steffl,Bagenal,Modeling
temporalvariabilityofplasma
conditionsintheIotorusduring
theCassiniera,J.Geophys.Res.,
109,A10216
2005 *Delamere,Bagenal,Steffl,Radial
variationsintheIoplasmatorus
duringtheCassiniera,J.Geophys.
Res.,110,A12223
2005 Smyth,Marconi,Natureofthe
iogenicplasmasourceinJupiter’s
magnetosphere.II.Near-Io
distribution,Icarus,176,138-154
2007 Wu,Hill,Wolf,Spiro,Numerical
simulationoffinestructureinthe
Ioplasmatorusproducedbythe
centrifugalinterchange
instability,J.Geophys.Res.,112,
A02206
2011 Smyth,Peterson,Marconi,A
consistentunderstandingofthe
ribbonstructurefortheIoplasma
torusattheVoyager1,1991GB,
andGalileoJ0epochs,J.Geophys.
Res.,116,A07205
Reviewofobservationsandmodelsofbothneutralcloudsandtorus.
Extensivediscussiononradialtransport.
CHIANTI Dustmeasurementsshowx1000increaseinfluxfromIoinSept2000
CassiniUVISseesdecreasefromOct2000throughMar2001.
Modeledwith2003modelwithfactorof3.5increaseinneutralproduction
ratewithtime-scaleof22.5days
CHIANTI ModeledUVIScompositionvs.radialdistancewith1-Dmodel(latitudinally
4.2
averaged)withproscribedneutralcloudprofile.Solvesforconservation
ofmass&energy
Parameters:SN,O/S,tau,Fehot,Tehot,
Exploressensitivitytotransport,neutralsource,Fehot.
NearIo–neutralcloudsofO,S–fromexobaseto~20RIo.
Limitedelectrodynamics.
Ionization&CHEX.Innervs.outerregion–seeFig10.
Netmass-loading111kg/s
RiceConvectionModelforIPT-modelsradialtransportwithflux-tube
interchange.
Nochemistry.
Found~1°longitude“fingers”.Outwardtransportfasterthaninward.
CHIANTI AttemptstomatchallVoyagerandGalileodatawitha4-Dmodelthat
5.2.1
includesIophase,SIIIlongitude,R,Latitude
EmphasisonS+emissions
ArguesforbigchangesinInner/Outertorusratiosbetweenepochs:
1991(GBepoch)outer/innerdensities~1.3xVoyager
1995(GLL)outer/innerdensities~3.9xVoyager
6
2011 Hess,Delamere,Bagenal,Schneider,
Steffl,Longitudinalmodulationof
hotelectronsintheIoplasma
torus,J.Geophys.Res.,116,
A11215
2014 Grieveetal.,Electron-impact
excitationcollisionstrengthsand
theoreticallineintensitiesfor
transitionsinSIII,Ap.J.,780,110
Longitudemodulationofemissions.
Arguesformagneticfieldcontrol.
SayshotelectronscomefromAlfveniccurrents.
Powerfrominward-movingfluxtubesisnotmodulatedbylongitude.
ToaccountforthebeatingbetweenSystemIII,SystemIV:
- SystemIVcontrolstheinwardmotionofemptyfluxtubes,
- SystemIIIcontrolsefficiencyofpowertransfertotheelectrons(via
magneticfieldvariationsatthefootofthefluxtubeintheionosphere).
CHIANTI CalculationsofcollisionstrengthsandexcitationoflinesofSIIIatvarious
7.1
regionsintheEUV
IncorporatedintoCHIANTIdatabase
Comparisonwithline-ratiosfromFeldmaninFUSE&EUVEobservations.
Alsodiscusseskappafunctions.
*Keypapers
GB=ground-based,DES=DonE.Shemansky,Fehot=fractionofhotelectrons,Thot=temperatureofhotelectrons
SI=SSII=S+SIII=S++SIV=S+++SV=S4+OI=OOII=O+OIII=O++OIV=O+++OV=O4+
NL2=NL2=fluxtubecontent
COREQ=COllisionalandRadiativeEQuilibrium
CITEP=ColoradoIoTorusEmissionsPackage
CHIANTI=http://www.chiantidatabase.org
CHEX=chargeexchange
1980–purplecoloreddatemeansalsoincludedunderUVemissionsbibliography
1992–greencoloreddatemeansalsoincludedunderTorusVariabilitybibliography
7