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Autumn MIST, 29 th November 2013 1 Autumn MIST, 29 th November, 2013 Oral Presentations (in talk order) The Met Office Unified Model and its extension to the thermosphere (INVITED) David Jackson, Met Office, Exeter, UK The Met Office Unified Model (UM) is a troposphere / stratosphere / mesosphere model which is used widely for both weather forecasting and climate studies. It includes a comprehensive representation of atmospheric dynamics, physics and chemistry, and currently has an upper boundary near 85 km. In order to develop an improved capability for space weather forecasts, it is desirable to develop a coupled system of models representing the domain from the Sun to the Earth's surface. Much space weather forecast research is focused on the thermosphere and ionosphere, since that is where many space weather impacts are seen. While the thermosphere and ionosphere are largely driven from above, recent research has shown that the coupling between this region and the lower atmosphere is also important. For example, non‐migrating tides forced in the tropical troposphere have been linked to variations in the ionospheric F region. Therefore, representation of such coupling is important. An attractive way of doing this is by building a "whole atmosphere" model, which spans the neutral atmosphere from the Earth's surface to the exobase (around 600 km) and represents the coupling between different atmospheric levels in a self‐consistent manner. Such a task is challenging, so an intermediate step may be to develop an extended model with an upper boundary in the lower thermosphere. This approach is more tractable while remaining scientifically useful. The UM is suitable for such developments since its dynamical core is non‐hydrostatic and uses a deep atmosphere approximation. In this presentation, the dynamical, physical and chemical developments required to make this extended model a reality are discussed. Physical models, empirical models and data in the ATMOP project Timothy Spain, Alan Aylward and the ATMOP Consortium The ATMOP project aims to improve the Drag Temperature Model (DTM) for better modelling of drag in satellite trajectory propagation. Through a combination of precise, but limited, accelerometer measurements and the global, but imperfect, UCL CMAT2 global circulation model, the global representation of thermospheric density in DTM is improved. The contributions to and strengths of CMAT2 in this effort will be highlighted.
Transcript of Autumn MIST, 29th November, 2013
AutumnMIST,29thNovember2013
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Autumn MIST, 29th November, 2013
Oral Presentations (in talk order) TheMetOfficeUnifiedModelanditsextensiontothethermosphere(INVITED)DavidJackson,MetOffice,Exeter,UKTheMetOfficeUnifiedModel(UM)isatroposphere/stratosphere/mesospheremodelwhichisusedwidelyforbothweatherforecastingandclimatestudies.Itincludesacomprehensiverepresentationofatmosphericdynamics,physicsandchemistry,andcurrentlyhasanupperboundarynear85km.Inordertodevelopanimprovedcapabilityforspaceweatherforecasts,itisdesirabletodevelopacoupledsystemofmodelsrepresentingthedomainfromtheSuntotheEarth'ssurface.Muchspaceweatherforecastresearchisfocusedonthethermosphereandionosphere,sincethatiswheremanyspaceweatherimpactsareseen.Whilethethermosphereandionospherearelargelydrivenfromabove,recentresearchhasshownthatthecouplingbetweenthisregionandtheloweratmosphereisalsoimportant.Forexample,non‐migratingtidesforcedinthetropicaltropospherehavebeenlinkedtovariationsintheionosphericFregion.Therefore,representationofsuchcouplingisimportant.Anattractivewayofdoingthisisbybuildinga"wholeatmosphere"model,whichspanstheneutralatmospherefromtheEarth'ssurfacetotheexobase(around600km)andrepresentsthecouplingbetweendifferentatmosphericlevelsinaself‐consistentmanner.Suchataskischallenging,soanintermediatestepmaybetodevelopanextendedmodelwithanupperboundaryinthelowerthermosphere.Thisapproachismoretractablewhileremainingscientificallyuseful.TheUMissuitableforsuchdevelopmentssinceitsdynamicalcoreisnon‐hydrostaticandusesadeepatmosphereapproximation.Inthispresentation,thedynamical,physicalandchemicaldevelopmentsrequiredtomakethisextendedmodelarealityarediscussed. Physicalmodels,empiricalmodelsanddataintheATMOPprojectTimothySpain,AlanAylwardandtheATMOPConsortiumTheATMOPprojectaimstoimprovetheDragTemperatureModel(DTM)forbettermodellingofdraginsatellitetrajectorypropagation.Throughacombinationofprecise,butlimited,accelerometermeasurementsandtheglobal,butimperfect,UCLCMAT2globalcirculationmodel,theglobalrepresentationofthermosphericdensityinDTMisimproved.ThecontributionstoandstrengthsofCMAT2inthiseffortwillbehighlighted.
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Fromopticalemissionstoauroralacceleration–usingthreemodelsSamTuttle,JohnSpry,BettyLanchester(presenting),BjörnGustavsson,HannaDahlgrenStartingwithselectedopticalemissionsfromasmallregionsurroundingthemagneticzenith,threemodelsareusedtoobtainatheoreticalunderstandingoftheaccelerationprocessesthatcreatetheseemissions.Thefirstmodelisacombinedionchemistryandelectrontransportmodel,whichprovidesapowerfulmethodforobtainingtheenergyandfluxoftheprecipitationinthemagneticzenith,usingselectedemissionsfromatomicoxygenandonemolecularsourceasinput.Thesecondmodelusesthecombinedopticalemissionsatthesetwodistinctwavelengthstovalidatetheenergyspectrainaregionsurroundingthemagneticzenith,bycomparingthemeasuredfastandvariableopticalemissionsataframerateof20fpsandspatialresolutiondownto20mwithmodelledvalues.Theresultingthreedimensionalemissionprofilesinthefieldofviewofthecamerasarethenusedtoextractopticalflowsfromathirdwavelengthemission,inthemetastableemissionat732nmfromO+ions.Finallytheseflowsareinterpretedassmallscaleelectricfieldsintheregionoftheauroralstructures,andareusedasinputtoaplasma‐neutralMHDmodeltocreateaccelerationbyparallelelectricfieldsgeneratedbycurrentstriationinthelowermagnetosphere.AglobalmodelofmeteoricmetalsJohnPlane,WuhuFeng,DanielMarsh,DiegoJanches,ErinDawkins,MartynChipperfield,JosefHoffner,FanYiandChesterGardnerAuniquefeatureofthemesosphere/lowerthermosphere(MLT)regionisthelayersofmetalatomsproducedbymeteoricablation.Theselayersprovideanimportantwaytounderstandthecouplingofatmosphericchemistryanddynamicalprocesses,aswellastestingtheaccuracyofclimatemodelsintheMLT.Wehavedevelopedthefirstglobalatmosphericmodelofmeteoricmetalsbycombiningthreecomponents:theWholeAtmosphereClimateCommunityModel(WACCM)fromtheUSNationalCenterforAtmosphericResearch;adescriptionoftheneutralandion‐moleculechemistryoffivemetals(Na,Fe,K,MgandCa)basedontheratecoefficientsofmorethan120reactionsmeasuredbytheLeedsgroup;andameteorinputfunctionwhichcombinestheLeedsChemicalAblationModelwithanastronomicalmodelofcosmicdustintheinnersolarsystem.Themodelhasbeenevaluatedagainstanumberofavailableground‐basedlidarmeasurementscoveringawiderangeoflatitudesinbothhemispheres,aswellaswithglobalobservationsoftheNaandKlayersusingtheOpticalSpectrographandInfra‐RedImagerSystem(OSIRIS)on‐boardtheOdinsatellite.Ingeneral,themodelperformswellinsimulatingthemesosphericatomicmetallayers(i.e.,thelayerpeakdensitiesandheights,totalcolumnabundances,andseasonalvariability),althoughtherearesomesignificantdiscrepancies:inparticular,themodeloverestimatesmetalionsabove95kmcomparedwithrocket‐bornemassspectrometricmeasurements.Themodelhasalsobeenrunfortheperiod1955‐2006toinvestigatehowchangingclimateandthesolarcycleimpactthedifferentmetallayers.
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Three‐dimensionalsimulationofcomplexplasmaenvironmentanditsapplicationF.Honary,A.Anuar,S.MarpleDustparticlesareubiquitousinspaceandearth’senvironmentandhavebeenasubjectofintensiveresearchfordecades.Dustinteractionwithlocalplasmapopulationincreasesthecomplexityoftheplasmasystemwhichiswhyitisreferredtoascomplexplasma.Inthispresentationanew3‐DparticleincellcodewithMonteCarlocollision(PIC‐MCC)willbereportedwhichiscapableofsimulatingthebehaviourofdustparticlesinspaceplasma.Thecodeconsidersthedustchargingprocessbyambientplasma.Resultsforbothsingledustanddustcloudchargingandtheassociatedplasmaresponsewillbepresented.Simulationofspacecraftcharginginthepresenceofadustcloudrevealsthatacloudofdustparticleclosetospacecraftsurfaceaffectsplasmadensitiesaroundthespacecraftaswellasthespacecraft’ssurfacepotential.Thesimulationsuggeststhatdustcloudcausesthesurfacetochargetohighernegativepotentialandthecombinationofsurfacepotentialanddustcloudpotentialproducesaregionoftrappedlow‐energyelectrons.TheSwarmMission:overviewY.V.Bogdanova,M.W.Dunlop,A.W.P.Thomson,S.Macmillan,H.Luhr,R.Floberghagen,R.Haagmans,G.Ottavianelli,G.PlankandtheSwarmteam.TheESASwarmmissionisathree‐spacecraft‘constellation’designedtoexplorebothexternalandinternalpartsoftheEarth'smagneticfieldinunprecedenteddetail.Launchisscheduledfor14November2013andwillplacethespacecraftintolow,polarEarthorbits.TheSwarmmissionwasdevelopedprimarilyasamagneticfieldmissions,howeveradditionalplasmaandelectricfieldinstrumentsonboardexpandsthescientificgoalsofthismission,providingmeasurementsofnear‐Earthplasmadensity,temperatureandvelocityaswellasofelectricfield.Themissionhasfourprimaryscienceobjectives:(1)Studiesofcoredynamics,geodynamoprocesses,andcore‐mantleinteraction,forexampletoproducehigh‐resolutioninternalmagneticfieldmodels;(2)Mappingofthelithosphericmagnetisationanditsgeologicalinterpretation;(3)Determinationofthe3‐Delectricalconductivityofthemantle;(4)Investigationofelectriccurrentsflowinginthemagnetosphereandionosphere.AsbothanEarthExplorermissionandanimportantresourceforspaceweatherscience,themissionhasattractedinterestfromboththegeomagneticandMISTcommunities.AnumberofproposedUKstudiesareintendedontopicsrelatingto:dataverification,modellingandexploitation.TheseactivitieswillsupportthewiderESASwarmlevel2datafacilitiesandsciencedataverificationandexploration.TheSwarmactivitieshighlightthecrucialroleofscienceinsupportingSwarmoperations,includingthepossiblecoordinationwithdatafromotherspacecraftandwithground‐basedobservations.ThispresentationwillprovideanESAoverviewofthemissionstatus,instruments,availabledata,andplannedUKstudies.UKcontributorstotheSwarmteaminclude:RutherfordAppletonLaboratory,BritishGeologicalSurvey,LiverpoolUniversity(R.Holme),EdinburghUniversity(K.Whaler,N.Olsen),BritishAntarcticSurvey(M.Freeman),UniversityCollegeLondon(A.Aruliah),ImperialCollegeLondon(J.Eastwood),LeedsUniversity(P.Livermore).
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Assessingtheeffectofspacecraftmotiononsingle‐spacecraftsolarwindtrackingtechniquesT.M.Conlon,S.E.MilanandJ.A.DaviesRecentadvancesinwide‐angleimagingbytheSolarMassEjectionImager(SMEI)onboardtheCoriolisspacecraftandmorerecentlybytheHeliosphericImagers(HI)aboardNASA'sSolarTErrestrialRElationsObservatory(STEREO),haveenabledsolarwindtransientstobeimagedandtrackedfromtheSunto1AUandbeyond.Inthispresentationweconsidertwoofthetechniquesthathavebeenusedtodeterminethepropagationcharacteristicsofsolarwindtransientsbasedonsingle‐spacecraftobservations,inparticularpropagationdirectionandradialspeed.Thesetechniquesusuallyassumethattheobservingspacecraftremainsstationaryfortheentiretimeduringwhichitobservesthesolarwindtransient.WedeterminetheinaccuracyintroducedbythisassumptionforthetwoSTEREOspacecraftandfindthatitcanbesignificant,andcanleadtoanoverestimationofthetransientvelocityasseenfromSTEREOAandanunderestimationasseenbySTEREOB.Thishasimplicationsforthepredictionorsolarwindtransientsat1AUandhenceisimportantforthestudyofspaceweather.TheradialevolutionofanICMESimonW.Good,RobertJ.ForsythPRESENTINGAUTHOR:SimonW.GoodCoronalmassejections(CMEs)arelargeeruptionsofmagneticfieldandplasmafromthesolaratmospherewhoseinterplanetarymanifestations(ICMEs)canbedetectedinsitubyspacecraftinthesolarwind.Thefleetofspacecraftcurrentlyexploringtheinnersolarsystemoffersunprecedentedopportunitiesforthemulti‐point,insituobservationofICMEs‐suchobservationsareleadingtoabetterunderstandingofICMEkinematicsanddynamics,andofhowICMEmorphologyandmagneticfieldstructureevolveduringpropagation.AnumberofstatisticalstudieshaveconsideredthepropertiesofICMEsobservedatdifferentradialdistancesfromtheSun,butfewhavetrackedtheradialevolutionofindividualeventsinsitu.InsituobservationsmadebyVenusExpressandWindofthesameICMEwhilstthetwospacecraftwereatnearperfectradialalignmentinOctober2010willbepresented.Weshowthat,between0.72and0.99AU,themagneticfluxropeembeddedinthisevent(i)travelsatanapproximatelyconstantspeed,(ii)displaysself‐similarradialexpansion,and(iii)expandsinradialwidthbyafactorof1.28:thisinsituexpansionfactorisingoodagreementwithanempiricalrelationforradialwidththatothershavederivedfromtheremotetrackingof(I)CMEsusingSTEREO’sHeliosphericImagers.
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StudyingSolarWindMagneticReconnectionEventsusingtheClusterSpacecraft’s4‐pointMeasurementCapability.
A.C.Foster,C.J.Owen,A.N.Fazakerly,I.J.Rae,C.Forsyth,A.Balogh,E.Lucek,H.Reme
Weusedetailedobservationsbythe4Clusterspacecrafttostudytransienteventsinthesolarwindwhichareapparentlyconsistentwithpreviousreportsofmagneticreconnectionevents.Theuseofdatafromthe4Clusterspacecraftallowsthethreedimensionalstructureofeventstobestudiedatsub‐secondresolution.
Previousstudieshaveconcludedthatactivesolarwindreconnectioncurrentsheetsarepredominatelystableoverscalesof100sREandtimescalesofafewhours.Theyconformtotheclassicmodelofaconfigurationofapairofoppositelydirectedexhaustjetswithinmagneticfieldreversalregion,asfirstidentifiedbyGosling(JGR,2005).
Wepresentacasestudyofaneventthatoccurredonthe2ndMarch2006,inwhichwetesttheconsistencyofthetemporalandspatialstructureofmagneticreconnectionfromlargescalestosmallscales.Weshowthatthereconnectionstructuresarenotsimilaroverrelativelysmall(~10,000km)scales,suggestingeitherthatthereconnectionmaynotbestructuredasinGosling(JGR,2005),orthatthesestructuresarenotnecessarilylargeinthesolarwind.Weconcludethattheanalysisdemonstratesthatourcurrentunderstanding,thatmagneticreconnectionisalargescaleprocessinthesolarwind,maynotholdforallcases.
Onthegenerationofmagnetosheathhighspeedjetsbybowshockripples
H.HietalaandF.PlaschkeTheterrestrialmagnetosheathisembeddedwithcoherenthighspeedjetsofabout1Reinscale,predominantlyduringquasi‐radialinterplanetarymagneticfield(IMF).Whenthesehighdynamicpressure(Pdyn)jetshitthemagnetopause,theycauselargeindentationsandfurthermagnetosphericeffects.Thesourceofthesejetshasremainedcontroversial.Oneoftheproposedmechanismsisbasedonripplesofthequasi‐parallelbowshock.Inthisstudy,wecombineforthefirsttimefouryearsofsubsolarmagnetosheathobservationsfromtheTHEMISmissionandcorrespondingNASA/OMNIsolarwindconditionswithmodelcalculationsofarippledbowshock.ConcentratingonthemagnetosheathclosetotheshockduringintervalswhentheanglebetweentheIMFandtheSun‐Earthlinewassmall,wefindthat(1)97%oftheobservedjetscanbeproducedbylocalripplesoftheshockundertheobservedupstreamconditions;(2)thecoherentjetsformasignificantfractionofthehighPdyntailofthemagnetosheathflowdistribution;(3)themagnetosheathPdyndistributionmatchestheflowfromabowshockwithripplesthathaveadominantamplitudetowavelengthratioofabout9%(~0.1Re/1Re)andarepresent~12%ofthetimeatanygivenlocation.
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Small scale particle dynamics in Kelvin Helmholtz waves at the Magnetopause: High time resolution Cluster observations
AliVarsani,ChristopherJ.Owen,AndrewN.Fazakerley,I.JonathanRae,ColinForsyth,AndrewP.WalshInteractionsbetweenthesolarwindandtheEarth'smagnetosphereatthemagnetopausearethekeytounderstandingthemixingofthesetwoplasmaregimes.DuringperiodsofnorthwardIMF,whenthereisexpectedtobeanabsenceoflowlatitudereconnectionatthemagnetopause,therearequestionsastohowthelowlatitudeboundarylayermaybepopulatedwithmagnetosheath‐likeplasma.Clustermulti‐spacecraftobservationshaveshowntheexistenceofnon‐linearwavesatthemagnetopausethatarethoughttoberesultsofKelvin‐Helmholtzinstability;thesewavescangrowandformrolled‐upvorticeswhichmaytransferthesolarwindplasmaintothemagnetosphere.However,theparticlebehaviouratsmallscalesisyettobefullyunderstood.InDecember2007,Clusterencounteredon‐goingwavesasthefourspacecraftcrossedtheEarth’sduskflankmagnetopausethroughitslowlatitudeboundarylayer.Duringthisevent,theparticleinstrumentsreturnedafull3Dplasmadistributiononceevery4sandthemagneticfieldwascloselyalignedwiththespacecraftspinaxis.Inthisstudy,wearethusabletousethe3Dparticledatatoreconstructnear‐fullpitchangledistributionofelectronsandionsatsub‐spinresolution.Thesehigh‐timeresolutionobservations(upto32timesfasterthannormalmodedata)providenewinsightsintoparticledynamicsduringtheinbound‐outboundmovementsofClusterintothemagnetosheath.Ouraimistounderstandtheplasmabehaviourduringthedevelopmentofnon‐linearwavegrowth,whichmaysubsequentlydevelopintorolled‐upvorticesfurtheralongthemagnetopausetowardsthenightside.Wepresenttheinitialresultsfromthisstudywhichhighlightmultipleregionsoffieldalignedparticlesobservedatthemagnetopausecrossingswithinthesewaves;andinvestigatethesesignaturesaspossiblereconnectionburstswithinthegrowingKHwaveswhichfacilitatetransferofmagnetosheathplasmaintothemagnetosphere.
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Magnetospheric‘magic’frequenciesasstandingmagnetopausesurfacewavesM.O.Archer,M.D.Hartinger,T.S.HorburyStatisticalandeventstudieshaveshownthatmagnetosphericULFwavesareoftenobservedatpersistentdiscretePc5frequenciesknownas‘magic’frequencies[seeMenk2011forarecentreview].Thesearethoughttobeeitherdirectlydrivenbymonochromaticsolarwindpressurefluctuationsorresonantlyexcitedglobal(cavity/waveguide)modesorstandingmagnetopausesurfacewaves,perhapsexcitedbylocalisedpressureenhancementsinthemagnetosheath.Todistinguishbetweenthesehypotheses,weidentifytransientjetsinthemagnetosheath(whichoccurabout2%ofthetime,predominantlydownstreamofthequasi‐parallelshock)andstatisticallyinvestigatethespectralresponseofthemagnetosphericmagneticfieldatgeostationaryorbit.Thebroadbandjetsdonotexhibitdiscretefrequenciesbutdodrivewavesatthediscretemagicfrequencies,withbothdirectandresonantdriving.Weshowthattheexpectedfundamentalfrequenciesofmagnetopausesurfaceeigenmodeshavetwopreferentialvaluesoverawiderangeofupstreamconditions,correspondingtofastandslowsolarwind,andthattheirharmonicsareingoodagreementwiththe‘magic’frequencies.Wealsoshowthatthewavesarelargelyinconsistentwithglobal(cavity/waveguide)modesoutsidetheplasmasphere.Thusweconcludethatthese‘magic’frequenciesaremostlikelyduetomagnetopausesurfaceeigenmodes.Menk,F.W.,MagnetosphericULFwaves:Areview,inThedynamicmagnetosphere,editedbyW.LuiandM.Fujimoto,IAGASpecialSopronBookSeries,pp.223–256,Springer‐VerlagBerlin,doi:10.1007/978‐94‐007‐0501‐2_13,2011.
AstatisticalstudyofmagnetosphericplasmamassloadingusingtheClusterspacecraftJ.K.Sandhu,T.K.YeomanandR.C.FearUsingClusterdata,fromtheWHISPERandCISinstruments,fortheintervalspanning2000‐2012,anempiricalmodeldescribingplasmamassdensitydistributionalongclosedgeomagneticfieldlinesintheplasmatrough(4.5≤L<9.5)isdetermined,withdependenceswithLshellandMLT(MagneticLocalTime)included.Themethodinvolvesindependentlymodellingfield‐alignedvariationsintheelectrondensityandaverageionmass,andcombiningthesetoinferthecorrespondingmodelformassdensity.Akeyresultobtainedistheinclusionofalocalisedpeakinelectrondensityclosetothemagneticequatorintheelectrondensitymodel,neglectedbypreviousmodels.Apossibleapplicationoftheempiricalmassdensitymodel,topredictULF(UltraLowFrequency)pulsationfrequenciesusingatime‐of‐flighttechnique,isalsointroduced.Furtherimprovementstothemassdensitymodel,involvingquantifyingdependenceswithsolarwindandgeomagneticactivity,arediscussed.
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LossesintheradiationbeltscausedbyEMICwavesTobiasKersten,RichardB.Horne,NigelP.Meredith,SarahA.GlauertElectromagneticIonCyclotron(EMIC)wavesareelectromagneticwavesatfrequenciesbelowthelocalhydrogencyclotronfrequency.EMICwavescancauseelectronlossintheradiationbelts,iftheirfrequencyisDopplershiftedtotheelectroncyclotronfrequencybytherelativemotionofthewavesandelectronsalongthefieldline.ThisenablestheEMICwavestoresonatewithhighenergyelectronsatenergiesgreaterthanabout500keVandtherebycausinglossesduetopitchanglescatteringintothelosscone.TodeterminehoweffectiveEMICwavesare,wecalculatedbounceaveragedpitchanglediffusionratesforanominalmodelbasedonouranalysisofdatafromthefluxgatemagnetometerontheCRRESsatellite,whichsampledEMICwavesintheequatorialregionfromaboutL=4.0uptoaboutL=7forlatitudesupto30°.Thediffusionrateswerecalculatedfor5levelsofkpbetween12‐18MLT.Wefoundthatthesewavescoulddiffuseelectronsintothelossconeveryeffectivelyatenergiesgreaterthanabout2MeVforpitchanglesuptoabout60°.ThediffusionrateswereincludedintheBASradiationbeltmodeltogetherwithlowerandupperbandchoruswaves.UsingthemodelwewereabletoshowthatEMICwavescauseasignificantreductionintheelectronfluxforhighenergiesforarangeofL‐shellsfromL=4.0–9.0butonlyforpitchangleslowerthan60°.
AnanalysisoftheeffectofsolarwinddriversontheBirkelandcurrentovalsobservedbyAMPEREJ.C.Coxon,S.E.Milan,L.B.N.Clausen,B.A.AndersonandH.KorthTheActiveMagnetosphereandPlanetaryElectrodynamicsResponseExperiment(AMPERE)techniqueutilisesmagneticfieldmeasurementsfromtheIridiumsatelliteconstellationtodeterminethelocationandstrengthoftheBirkelandcurrents.Wecharacterisethelocationsoftheregion1and2Field‐AlignedCurrent(FAC)ovals,givingusaproxyforthesizeofthepolarcapandprovidingameasureoftheopenmagneticfluxcontentofthemagnetosphere.Usingthismeasurement,weinvestigatetherelationshipbetweeninterplanetaryconditionsanddynamicsinthesolarwind‐magnetosphere‐ionospherecoupledsystem.Specifically,wefocusonalarge‐scalestatisticalanalysisofchangesinthecurrentmagnitudesduringexpansionsandcontractionsofthemagnetosphericpolarcap.Therelationshipbetweenthesolarwinddrivingandtheobservedcurrentsisexploredinthecontextoftheexpanding/contractingpolarcapparadigm.
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EvidencefortheionosphericoutflowinSaturn’smagnetotailM.Felici,C.S.Arridge,A.J.Coates,M.K.DoughertyTheCassinimissionhasorbitedSaturnsince2004,butin2006itexploredthedeepmagnetotail,reachingdistancesofabout68RS.Variousstudieswerecenteredonplasmaparameters[Thomsenetal.,2010],sub‐corotationalplasma[Arridgeetal.,2009;McAndrewsetal.,2009],magneticfieldinthetail[JackmanandArridge,2011],reconnectionandplasmoids[Jackmanatal.,2007;Hillatal.,2008;Jackmanetal.,2008],SolarWindeffectsonSaturn’smagnetosphere[Arridgeatal.,2008],anditseffectsonSaturn’smagnetotail[Jackmanetal.,2010].InthispresentationwefocusondatafromCassiniwhenthespacecraftwassituatedat~2200hoursSaturnlocaltimeat30RSinSaturn’smagnetotail.Duringseveralentriesintothemagnetotaillobe,coldionsandelectronswereobserveddirectlyadjacenttotheplasmasheetandapparentlyextendingintothelobe.Theelectronsandionsappeartobedispersed,droppingtolowerenergieswithtime.Themagneticfieldhasaswept‐forwardconfigurationwhichisatypicalforthisregion.InthepresentationweexplorethehypothesisthattheseobservationsareevidenceofpolarionosphericoutflowfromSaturn[e.g.,Gloceretal.,2007].
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Poster Presentations (in alphabetical order) Large,sustainedverticalwindsinthemagneticcuspA.L.Aruliah,A.Ronksley,T.C.Spain,H.Carlson,K.OksavikUCL,UtahandBergenThispaperwillpresentobservationsfromthreeFPI‐EISCATcampaignsonSvalbardwhichsupportamechanismtoexplaintheunexpecteddensityenhancementsseenoverthemagneticcuspbytheCHAMPsatellite.Theproposedmechanismrequiresthatsoftparticleprecipitationincreasestheconductivityat150‐200kmaltitudeandsimultaneouslythereshouldbeburstsoffastplasmaconvectiontoprovidestrongfrictionalheating.Heatingatthishighaltitudemeansthatitrequireslittleenergytolifttherarefiedgasabove,andtherebybringdenserairintotheregionpassedthroughbyCHAMP(~400km).Saturn’sauroraldynamicsduringthe2013observingcampaign:insituandremoteobservationsS.V.Badman,E.J.Bunce,H.Melin,T.Stallard,J.D.Nichols,D.G.Mitchell,W.S.Kurth,F.J.Crary,MarciaBurton,K.H.Baines,R.H.BrownandM.K.DoughertyDuringtherecentSaturnauroralobservingcampaigninApril‐May2013theHubbleSpaceTelescope(HST)andground‐basedinfraredtelescopesobservedSaturn’snorthernaurorawhileCassiniinstrumentsobservedeitherthenorthernorsouthernaurorae.Thisprovidedopportunityforunprecedentedsimultaneousobservationsoftheauroralmorphologyandintensityinbothhemispheres,aswellascomplementarysamplingoftheemissionsatdifferentspatial,spectral,andtemporalscales.WefocusonobservationsoftheinfraredauroralemissionsmadebytheCassiniVisualandInfraredMappingSpectrometer(VIMS).Wepresentexamplesofrotatingandpoleward‐movingauroralblobs,aswellasverynarrow,wavy,andbifurcatedarcs.Weshowthecorrespondenceofthedifferentfeatureswithdetectionsofupwardanddownwardfield‐alignedcurrentsinthemagneticfield,plasmawave,andenergeticparticledata,andtheirdifferencesfromimagesoftheUVaurora.
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AFinite‐DifferenceTime‐DomainModelofElectromagneticWaveInteractionwithanIonosphericPlasmaPatrickCannon,FaridehHonaryExperimentsinartificialmodificationoftheEarth’sionospherebyradio‐frequency(RF)heatinghaveobservedsignificantenhancementoftheelectrontemperaturearoundtheupper‐hybridresonanceregion.ThemagnitudeofthistemperatureenhancementhasbeenfoundtobestronglydependentontheinitialangleofpropagationoftheRFpumpwaverelativetothegeomagneticfielddirectionandtheverticalelectrondensitygradient,andisthoughttobelinkedtotheformationandgrowthofdensity‐depletedirregularities.Thisposterdescribesamulti‐GPUFinite‐DifferenceTime‐DomaincodewhichhasbeendevelopedtosimulatetheinteractionbetweenanRFwaveandionosphericplasma.Thecodecouplestheelectromagneticequationswiththeplasma‐fluidequationsdescribingtemperatureanddensityandallowstheevolutionoftemperatureanddensityperturbationstobesimulated.Resultsofthesimulationofasimpleionosphericheatingexperiment,inwhichanO‐modepolarizedEMwavewaslaunchedatvaryinganglesintoavertically‐inhomogeneousionosphericplasmawithsmall(<5%)densityirregularitiesseededaroundtheO‐modereflectionheight,arepresented.Theresultsdemonstrateanangulardependenceinthegrowthrateofirregularities,withthemostsignificantgrowthoccurringwhentheincidentpumpwaveisdirectedclosetothemagneticzenith.
SphericalHarmonicAnalysisandClimatologicalAveragingofSuperMAGData
G.Dorrian,J.A.Wild,M.P.Freeman,J.W.Gjerloev
Wepresentearlyresultsbothforasphericalharmonicanalysis(SHA)ofinstantaneousgeomagneticconditionsandalongertermclimatologicalanalysisoftheEarth'smagnetosphereusingdatafromtheSUPERMAGnetwork.AmethodologyispresentedforcomparingmodeloutputsfromtheSHAwithSuperMAGdatatoinvestigatewhichorderofsphericalharmonicexpansionbestrepresentsthegeomagneticfieldundergivensolar‐terrestrialconditions.Wealsopresentaclimatologicalanalysisbyusingtime‐averagingofSUPERMAGstationdataoverextendedperiodsofthemostrecentsolarcycle.
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TheinteractionbetweentranspolararcsandcuspspotsR.C.Fear,S.E.Milan&R.MaggioloTranspolararcsandcuspspotsarebothauroralphenomenathatoccurwithinthepolarcap(i.e.polewardofthemainauroraloval)duringperiodswhentheinterplanetarymagneticfieldisnorthward.Transpolararcsarelarge‐scaleauroralfeatureswhichextendfromthenightsideovaltowardsthedayside,oftenconnectingtothedaysideoval;theyareformedbytheclosureoflobefluxbymagnetotailreconnection,andhenceindicatethe'trapping'ofclosedmagneticfluxwhichisembeddedwithinthelobe.Whenatranspolararcdoesconnecttothedaysideoval,thisindicatesthatallofthemagneticfluxinanarrowlocaltimesectorinthemagnetotailisclosed.Cuspspotsareemissionsatthefootprintofalobereconnectionsite;hencetheyindicatetheoccurrenceofsinglelobereconnection,whichredistributesopenmagneticfluxinthelobe,causingflowsinthelobeandpolarcap.Akeyfeatureofsinglelobereconnectionisthatitdoesnotchangethenettopologyofthemagneticfluxinthemagnetosphere(i.e.thereisnonetopeningorclosureofflux).However,thetwophenomenaarelinked,asthecirculationoflobemagneticfluxinstigatedbylobereconnectioncausesthemotionoftranspolararcs.WepresentfurtherobservationsfromtheIMAGEsatelliteon15thSeptember2005,duringwhichtimeatranspolararcisobservedtointersectwithacuspspot.Wearguethatsincecuspspotsandmotionoftranspolararcsarebothmanifestationsoflobereconnection,thisshouldbearelativelycommonoccurrence.Wedemonstratethatwhenthisinteractionoccurs,thetopologiesassociatedwithsinglelobereconnectionchange,andhenceithastheneteffectofopeningclosedmagneticfluxinthemagnetotail.Finally,weshowthatthereconnectionmechanismpostulatedtoexplaintheformationoftranspolararcsisalsocapableofexplainingtheexistenceofsucharcsatmultiplelocationswithinthepolarcap.
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In‐situspatio‐temporalmeasurementsofthedetailedsubstructureofthesubstormcurrentwedgeanditsevolutionC.Forsyth,A.N.Fazakerley,I.J.Rae,C.E.J.Watt,K.Murphy,J.A.Wild,T.Karlsson,R.Mutel,C.J.Owen,R.Ergun,A.Masson,M.Berthomier,E.Donovan,H.U.Frey,J.Matzka,C.Stolle,Y.ZhangThesubstormcurrentwedge(SCW)isafundamentalcomponentofgeomagneticsubstorms.ModelstendtodescribetheSCWasasimplelinecurrentflowingintotheionospheretowardsdawnandoutoftheionospheretowardsdusk,linkedbyawestwardelectrojet.Weusemulti‐spacecraftobservationsfromperigeepassesoftheCluster1and4spacecraftduringasubstormon15Jan2010,inconjunctionwithground‐basedobservations,toexaminethespatialstructuringandtemporalvariabilityoftheSCW.Atthistime,thespacecrafttravelledeast‐westazimuthallyabovetheauroralregion.WeshowthattheSCWhassignificantazimuthalsub‐structureonscalesof100~kmataltitudesof4,000‐7,000km.Weidentify26individualcurrentsheetsintheCluster4dataand34individualcurrentsheetsintheCluster1data,withCluster1passingthroughtheSCW120‐240~safterCluster4at1,300‐2,000kmhigheraltitude.Bothspacecraftobservedlarge‐scaleregionsofnetupwardanddownwardfield‐alignedcurrent,consistentwiththelarge‐scalecharacteristicsoftheSCW,althoughsheetsofoppositelydirectedcurrentswereobservedwithinbothregions.Weshowthatthemajorityofthesecurrentsheetswerecloselyalignedtoanorth‐southdirection,incontrasttotheexpectedeast‐westorientationofthepre‐onsetaurora.Comparingourresultswithobservationsofthefield‐alignedcurrentassociatedwithburstybulkflows(BBFs)weconcludethatthestructuringoftheSCWcannotsolelybeduetoBBFdriven"wedgelets".OurresultsthereforerepresentconstraintsonfuturemodellingandtheoreticalframeworksonthegenerationoftheSCW.
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ForeshockDynamicsControlledbyHotFlowAnomaly:RelationbetweenDawnandDuskSectorEventsC.Foullon,I.Dandouras,H.Kucharek,B.Lavraud,C.Mazelle,S.RochelGrimald,C.CarrandA.N.FazakerleyOn21January2005,thepassageinthemagnetosphericdawnsectorofatiltedsolarwindcurrentsheetattheperipheryofanInterplanetaryCoronalMassEjectionisnotobservedbyClusterinthedusksector,wheretheInterplanetaryMagneticFieldpointsinsuchawaytoformaforeshock.ItcoincideshoweverwiththemomentarytransitionofClusterfromafield‐alignedbeamregionintoaUltra‐Low‐Frequency(ULF)wavefield,withfirsteverreported6s‐periodsinthespacecraftframe.The4‐spacecraftClusteranalysisshowsthattheULFwavesareintrinsicallyleft‐handedandpropagatingdownstreamintheprotonplasmaframe,andthuscannotbeproducedbythelocalupstream‐directedfield‐alignedprotonbeam.Moreover,oneachsideofthemagnetosphere,DoubleStarTC‐1andGeotailexperiencelargevariationsinmagnetosheathplasmaparametersconsistentwiththetailwardeffectsofaHotFlowAnomaly(HFA)expectedasaresultoftheinteractionwiththecurrentsheet.ModellingofthebowshockandforeshockdynamicsshowsthattheentryintotheforeshockULFwavefieldrequiresanexpansionofthebowshockshape,consistentwiththeexpectedformationofaHFAbulge.WeproposethatthegenerationoftheidentifiedULFwavesonthedusksideiscontrolledbytheproductionofbeamsofenergeticparticles,sufficientlyhotfortheion/ionlefthandresonantinstabilitytoemerge,consistentwiththoseparticlesbackstreamingdownstreamtowardsClusterfromapresumedHFAexpansioninthesolarwind. Modelling the high‐energy electron flux throughout the radiation belts using the BAS Radiation Belt model S.A.Glauert,R.B.Horne,N.P.Meredith,T.KerstenThefluxofrelativisticelectronsintheEarth'sradiationbeltsishighlyvariableandcanchangebyordersofmagnitudeontimescalesofafewhours.Understandingthedriversforthesechangesisimportantasenergeticelectronscandamagesatellites.TheBASRadiationBeltmodelisaphysics‐basedmodelthathasbeendevelopedtosimulatetheenergeticelectronfluxthroughouttheradiationbelts,incorporatingtheeffectsofradialtransport,wave‐particleinteractionsandcollisions.ItisnowusedtoforecasttheenergeticelectronfluxaspartoftheEU‐FP7SPACECASTproject.HereweapplyanewversionoftheBASRadiationBeltmodeltodifferenttypesofspaceweatherevents.Weshowthatanewmodelforplasmaspherichissandlightning‐generatedwhistlerscanreproducethequiettimedecayoftheelectronfluxintheslotregion,wherethenewO3Bsatelliteswilloperate.WealsodemonstratethatthelargeincreasesinfluxthatcanbeobservedduringbothCMEandCIRdrivenstormsintheheartoftheradiationbelts,whereGNSSsatellitesoperate,arewellreproducedusingarecentlypublishedmodelforupperandlowerbandchoruswaves.Finally,usingsolarwinddata,wemodelchangesintheouterboundaryoftheEarth’smagneticfieldandshowhowthesechangescancauserapidradiationbeltlossesmuchclosertotheEarththatcanaffectsatellitesinbothMEOandGEOorbits.
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TheinfluenceofIMFclockangletimescalesincontrollingthenatureofhigh‐latitudeionosphericconvectionAdrianGrocottandSteveMilanReconnectionbetweentheterrestrialandinterplanetarymagneticfields(IMF),andsubsequentreconnectioninthemagnetotail,driveslarge‐scalecirculationofthemagnetosphere,andleadstorelatedpatternsofconvectionofthehigh‐latitudeionosphericplasma.Daysideandnightsidereconnectioneachdriveacomponentoftheflowwhichcombinetoproducetheinstantaneousconvectionpattern(CowleyandLockwood,1992).Lockwoodetal.(1986),KhanandCowley(1999)andothersshowedthattheionosphericresponsetoachangeindaysidecouplingpropagatesaroundthepolarcapin10‐15minstoestablishanewsteadystateconvectionpattern.Averageconvectionpatterns,using36minutesasthetimescaleforsteadyIMF(RuohoniemiandGreenwald,2005),failtoadequatelyresolvecertainknownfeaturesoftheconvection,suchashigh‐latitudereverseconvectioncells,andnightsideflowsresultingfromtailreconnectionduringIMF‐northward,non‐substormintervals(TRINNIs).UsingobservationsoftheionosphericconvectionmadebytheSuperDualAuroralRadarNetwork(SuperDARN)wediscusslongertimescalechangesthatoccuriftheIMFremainssteadyformanyhoursinagivenorientation.OuranalysisshowsthatanumberofconvectionphenomenaarebetterdescribedwhentakingvariableIMFtimescalesintoaccountandhelpstoelucidatethemechanismsthatdrivethem.Saturn’smagnetosphericdynamics:AstudyoftailreconnectionsignaturesC.M.Jackman,J.ASlavin,M.G.Kivelson,D.J.Southwood,N.Achilleos,M.F.Thomsen,G.A.DiBraccio,J.P.Eastwood,M.P.Freeman,M.K.DoughertyThePioneer11(1979),Voyager1(1980)andVoyager2(1981)spacecraftglimpsedSaturn’smagnetotailontheirflybysandprovidedthefirstcluesastoitscharacterandextent.SubsequentlytheCassinispacecraftatSaturn(2004‐2017ascurrentlyplanned)hasshedhugelightonthisfascinatingandcomplexenvironment.Inparticularthedeeptailorbitsof2006providedanopportunitytostudydynamicssuchasmagneticreconnectioninthetail,andtosamplechangingplasmaflowsandfieldtopologyinsitu.IwillprovideanoverviewofmyworkonSaturn’smagnetotail,withastrongfocusonmagnetotailreconnection,includingobservationsofplasmoids,travellingcompressionregionsanddipolarizations.Iwilldescribethestatisticalpropertiesofreconnectionsignaturesinsitu,andexplaintheeffectsofreconnectiononglobalmagnetosphericdynamicsatSaturn.
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Multiple‐SpacecraftDensityMeasurementsofTurbulenceintheFastSolarWind:PreliminaryFindingsLaurenJeska,XingLi,OwenRobertsInvestigationsintosolarwindturbulencesuggestthatalargeproportionoftheenergyisAlfvénic(incompressible)atinertialscales.Atsmallerionandelectronscales,thepropertiesofturbulencearestillunderdebate,althoughmanybelievethatKineticAlfvénwavesaredominant.Thepropertiesoftheremainingcompressibleturbulencearealsocontended.UsingdatafromthefourClusterspacecraft,thepoweratdifferentfrequencies,anditsdistributionink‐space,canbemeasuredwithoutassumingthevalidityofTaylor'shypothesis.Thisisimportanttoidentifyorruleoutweakturbulencecomponents,whichcannotreadilybedeterminedbysingle‐spacecraftmeasurements.Forthefirsttime,k‐filteringisappliedtoevaluatethepowerfromWHISPERelectrondensitymeasurements,andthisiscomparedtothepowerin|B(t)|ationscales.AstheWHISPERmeasurementshaveacadencyofonly2.2s,dataderivedfromaproxymeasurement,thespacecraftpotentialmeasuredbytheEFWinstrument,arealsoinvestigated.Thesedatahaveahighercadencyof0.2s.Wavenumberanisotropyinspectra,statisticsandscalingintheturbulentsolarwindusingalocallydefinedbackgroundmagneticfieldKhuromH.Kiyani,KareemT.OsmanandSandraC.ChapmanOneofthekeycharacteristicsofsmall‐scaleplasmaturbulencewithinthesolarwindthatdistinguishesitfromhydrodynamicneutralfluids,isthatthemajorityofthepowerissituatedinspatialfluctuations(wavenumbers)thatareperpendiculartothebackgroundmagneticfield.Asthesefluctuationsrepresentspatialgradients,thishasbeeninterpretedastheturbulentcascadeproceedingprimarilyorexclusivelyperpendiculartothebackgroundmagneticfield.However,definitionsofwhatconstitutesabackgroundmagneticfieldfortheturbulentmagneticfluctuationslackconsensusandthistopicisasubjectofdebateamongstresearcherswhostudyturbulence–awell‐knownmultiscalephenomenonwherethereisnoclearseparationofscales.Anappropriateandself‐consistentdefinitionofsuchabackgroundfieldisessentialifonedesirestocompareobservationalresultswiththeoreticalanalysisandpredictions–necessaryforadeeperunderstandingofplasmaturbulence.WeemploytheuseoftheUndecimatedDiscreteWaveletTransform(UDWT)toseparateoutthesignalintoascaledependentlocalbackgroundmagneticfield,andscale‐dependentlocalfluctuations.TheUDWTnotonlydecomposesthesignalsintocomponentsfluctuatingatdifferentscales,butcruciallyalsopreservesthetimingofeventswithinsignals.Thisallowsonetoprojectthefluctuationsaccuratelyontoalocallyvaryingbackgroundmagneticfield.WeusesolarwindmeasurementsfromtheULYSSESandSTEREOspacecraftmissionstoillustratethekeyconcepts.
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Mechanismsbywhichtheinterplanetarymagneticfieldinfluencespolarandmid‐latitudesurfaceatmosphericpressureMaiMaiLam,GarethChishamandMervynPFreemanTheexistenceofameteorologicalresponseinthepolarregionstofluctuationsintheinterplanetarymagneticfield(IMF)componentByiswellestablished.Morecontroversially,thereisevidencetosuggestthatthisSun‐weathercouplingoccursviatheglobalatmosphericelectriccircuit.Consequentlyithasbeenassumedthattheeffectmaximizesathighlatitudesandisnegligibleatlowandmidlatitudes,becausetheperturbationbytheIMFisconcentratedinthepolarregions.WedemonstrateapreviouslyunrecognizedinfluenceofIMFByonmid‐latitudesurfacepressure.ThedifferencebetweenthemeansurfacepressureduringtimesofhighpositiveandhighnegativeIMFBypossessesastatistically‐significantmid‐latitudewavestructuresimilartoatmosphericRossbywaves.OurresultsshowthatamechanismthatisknowntoproduceatmosphericresponsestotheIMFinthepolarregionsisalsoabletomodulatepre‐existingweatherpatternsatmidlatitudes.Wesuggestthemechanismforthisfromconventionalmeteorology(thismechanismisviableinprincipleforcommunicatinganyinfluenceofsolarvariabilityonpolaratmosphericpressuretothemidlatitudes).Theamplitudeoftheeffectiscomparabletotypicalinitialanalysisuncertaintiesinensemblenumericalweatherprediction.Thusarelativelylocalizedsmall‐amplitudesolarinfluenceontheupperatmospherecouldhaveanimportanteffect,viathenonlinearevolutionofatmosphericdynamics,oncriticalatmosphericprocesses.Saturn’sdaysideUVauroras:EvidenceformorphologicaldependenceonthedirectionoftheupstreaminterplanetarymagneticfieldC.J.Meredith,I.IAlexeev,S.V.Badman,E.S.Belenkaya,S.W.H.Cowley,M.K.Dougherty,V.V.Kalegaev,G.R.Lewis,andJ.D.Nichols.WeexamineauniquesetofsevenHubbleSpaceTelescope(HST)imagingintervalsofSaturn’snortherndaysideUVaurorasexhibitingusual‘oval’morphologies,duringwhichCassinisimultaneouslymeasuredtheIMFupstreamofSaturn’sbowshockoverintervalsofseveralhours.Theseaurorasgenerallyconsistofadawnarcextendingtowardsnooncentrednear~15co‐latitude,togetherwithintermittentpatchyformsat~10co‐latitudeandpolewardthereof,locatedbetweennoonanddusk.Thedawnarcisapersistentfeature,butexhibitsvariationsinposition,width,andintensity,whichhavenoclearrelationshipwiththeconcurrentIMF.However,thepatchypost‐noonaurorasarefoundtorelatetothe(suitablylaggedandaveraged)concurrentIMFBz,beingpresentinallfourintervalsofpositiveBzandabsentinallthreeintervalsofnegativeBz.ThemostcontinuoussuchformsoccurinthecaseofstrongestpositiveBz.Theseresultssuggestthatthepost‐noonformsareassociatedwithreconnectionandopenfluxproductionatSaturn’smagnetopause,relatedtothesimilarly‐interpretedsmall‐scalestructuresobservedpreviouslyinthisLTsectorinCassiniUVISdata,whosedetailsremainunresolvedintheseHSTimages.OneoftheintervalswithnegativeIMFBz,however,exhibitsapre‐noonpatchofhigh‐latitudeemissionextendingpolewardofthedawnarctowardsthemagnetic/spinpole,suggestiveoftheoccurrenceoflobereconnection.Overall,thesedataprovideevidenceofsignificantIMF‐dependenceinSaturn’sdaysideauroras,aresultthatshouldbefollowedupifmoresuchsimultaneousdatabecomeavailable.
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Observationsofmesosphericgravitywavesfromaship‐borneimagerT.Moffat‐Griffin,N.C.Cobbett,M.Rose,P.Breen,T.Stroud,R.E.HibbinsPerturbationsinairglowareacommonwaytoobservemesosphericgravitywavesfromtheground.Thispresentationdetailsthedevelopmentofanovelship‐borneairglowimagersystemthatwillallowthefirstmeasurementsofmesosphericgravitywavesabovetheoceanstobeperformedfromaship.NumericalModellingofnonlinearwaveparticleinteractionsinobliquewhistlersDNunnandYOmuraNonlinearwaveparticleinteractionsinparallelpropagatingwhistlershasbeeninvestigatedextensivelyintheoryandbynumericalmodelling.Hereweinvestigateindetailbynonselfconsistentcomputationnonlinearwpiinobliquewhistlersforawavefieldthatisnarrowbandbutmaybecompletelyarbitraryasfarasspacetimedependenceofpropagationangle,frequencyandwaveamplitudego.Thewavefieldsuiteincludesadetailedmodelofachoruselement.Unlikepreviousworksweprogressfromtrajectorycomputationstocomputationofresonantparticledistributionfunction,resonantparticlecurrentandnonlineargrowthrates,andthisforANYresonanceorder'n'.LandaudampingandcyclotrongrowthareexaminedforchoruselementsandforCWwavefieldsandimportantresultssecured.ThecodeiswritteninFortran90andusingMPIrunsinabout2hoursonSouthamptonUniversityIRIDISsupercomputersystem.ProtonKineticEffectsandTurbulentEnergyCascadeRateintheSolarWindK.T.Osman,W.H.Matthaeus,K.H.Kiyani,B.Hnat,andS.C.ChapmanThekineticprocessesarisingfromnon‐thermalvelocitydistributionfunctionscanaffectthemacroscopicevolutionofspaceplasmas.WepresentthefirstobservedconnectionbetweenkineticinstabilitiesdrivenbyprotontemperatureanisotropyandestimatedenergycascaderatesintheturbulentsolarwindusingmeasurementsfromtheWindspacecraftat1AU.Wefindenhancedcascaderatesareconcentratedinregionsofhightemperatureanisotropy,whichincludesthosetheoreticallyunstabletothemirrorandfirehoseinstabilities.Astrongcorrelationisobservedbetweentheestimatedcascaderateandkineticeffectssuchastemperatureanisotropyandplasmaheating,resultinginprotons5‐6timeshotterand70‐90%moreanisotropicthanundertypicalisotropicplasmaconditions.Theseresultsoffernewinsightsintokineticprocessesinaturbulentregime.
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AnisotropicIntermittencyofMagnetohydrodynamicTurbulenceK.T.Osman,K.H.Kiyani,B.Hnat,andS.C.ChapmanAhigher‐ordermultiscaleanalysisofspatialanisotropyininertialrangemagnetohydrodynamicturbulenceispresentedusingmeasurementsfromtheSTEREOspacecraftinfastambientsolarwind.Weshowforthefirsttimethat,whenmeasuringparalleltothelocalmagneticfielddirection,thefullstatisticalsignatureofthemagneticandElsasserfieldfluctuationsisthatofanon‐Gaussiangloballyscale‐invariantprocess.Thisisdistinctfromtheclassicmulti‐exponentstatisticsobservedwhenthelocalmagneticfieldisperpendiculartotheflowdirection.Theseobservationsareinterpretedasevidencefortheweakness,orabsence,ofaparallelturbulentenergycascade,asisconsistentwithseveraltheoreticalmodels.Assuch,theseobservationspresentstrongobservationalconstraintsonthestatisticalnatureofintermittencyinturbulentplasmas.PlanetaryPeriodOscillationsinSaturn’smagnetosphere:ComparisonofmagneticoscillationsandSKRmodulationsinthepost‐equinoxintervalG.Provan,L.LamyandS.W.H.CowleyWepresentacomparisonofSaturn'splanetaryperiodoscillationsfromtwoCassinidatasets;themagneticfieldandSaturnkilometricradiation(SKR).ThroughouttheCassinimissionthereisgoodoverallagreementbetweentheperiodsdeterminedfromthetwodatasets,thoughwithsomeunexplaineddiscrepanciesoccurring,especiallyaroundequinox.Bothdatasetsshowtwodistinctoscillationsatclosetotheplanetaryperiod.Todate,inOctober2013,thenorthernperiodhasremainedshorterthanthesouthernalthoughthetwoperiodscloselyconverged(butdidnotcross)post‐equinox.StartinginFebruary2011themagneticoscillationsdisplayedanewbehaviouralregime,withabruptchangesintheamplitudesoftheoscillationsandsmallerchangesintheirperiodsoccurringapproximatelyevery6‐8months.Thefirstabruptchangeresultedintheunexpectedresumptionofsouthernoscillationdominancewithinthecoreregion.InAugust2011therewasanotherabruptchangetonortherndominance.DuringCassini'sequatorialorbitswereportcorrespondingnear‐simultaneoussharpchangesinthepeaksoftheSKRspectrogram,withtheratioofthenortherntothesouthernmagneticamplitudesbeingsimilartotheratioofthenortherntothesouthernSKRpeaks.SimultaneouschangesinthebehaviouroftheSKRandmagneticoscillationswerelessdiscerniblewhenCassinicommencedhigh‐latitudeorbits,presumablyduetostrongvariationsinthevisibilityoftheSKRemissionsalongCassini'sorbit.Duringthesepost‐equinoctialintervalstherewascloseagreementbetweentheperiodsoftheSKRandmagneticoscillationswhentheSKRspectrogrampeakswerehigh.
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ObservationofanAlfvénvortexinthesolarwindationkineticscalesOwenRoberts,XingLi,BoLiThesolarwindmagneticfieldpowerspectrausuallyconsistsofseveralpower‐laws,indicatingtheexistenceofnon‐linearplasmaturbulentcascade.Inthispaper,magneticfielddatafromtheClustermissionduringanundisturbedintervalofslowsolarwindisanalyzedat0.3Hz,nearthespectralbreakpointbetweentheioninertialanddissipationrangeswherethenatureofturbulencehasfundamentalimportancetoourunderstandingofplasmaturbulence.AssumingTaylor’sfrozenincondition,thefrequencycorrespondstoaprotonkineticscalekvA=Ωp∼0:38,wherethevAandΩparetheAlfvénspeedandprotonangulargyrofrequency,respectively.DatashowsthattheClusterspacecraftpassedthroughaseriesofwavepackets.WepresentthefirstclearevidenceofAlfvénvortexattheionkineticscaleinthesolarwind:anobservedstrongandrelativelyisolatedwavepacketisduetothefourClustersatellitescrossinganAlfvénvortex,anonlinearsolutiontotheincompressibleMHDequations.
ModellingTotalElectronContent(TEC)inequatorialPlasmasphereutilisingelectrondensitydatafromDoubleStar(TC1)missionAliyuthumanSadhique,DrAndrewBuckleyTheTC1spacecraftoftheDoubleStarmissionprovidesauniqueopportunitytoanalysetheTotalElectronContentprofileinthealtituderangebetween35000–22000kmwhichcorrespondstogeosynchronousorbitalaltitudeandGPSsatellites’altitude.TECcontributionofthisaltituderegionintrans‐plasmasphericradiotransmissionshasbeenhardtodetermineduetoabsenceofempiricaldata.TheTC1spacecraftoftheDoubleStarmission(JointChinese‐ESAprogramtostudytheSun–Earthinteraction/magnetosphere)operatedfrom2003till2007.Ithadanorbitof570x78970kmwith28.5°inclinationtotheequator.Ithad8instrumentsfromtheESA/NASAClustermission.AnewmethodologyisproposedtomakeuseoftheelectrondensitydataavailablefromtheTC1missiontoderiveTECprofilesalongtheorbitaltraceofthespacecraft.Thelowperigeeoftheorbitandthesmallerincidentangletheorbitaltracemakeswhileinthe35000‐22000kmaltituderangeresultingfromitprovidetheidealopportunitytoutilisethein‐situmeasurementsforTECcalculations.Themethodologyisdevisedasbelow:1 Theorbitaltracethroughthealtitude22000kmto35000kmisconsidered.2 Thespacecraftpassesthisregionin1hourand7minutes(4020seconds‐weconsider4000seconds)3 Meanelectrondensitiesarecalculatedevery40seconds,equalling10spins.
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4 Ifthevariationinelectrondensitywithinthat40secondsperiodisgreaterthan10%,theperiodisdividedbytworepetitivelytillthevariationis10%.5 Thedistancecoveredinevery40secondiscalledaTECBar6 Ifthevariationturnsouttobemorethan10%withinthatbar,halvedsubbarsareconsidered.(Asin4above)7 TheorbitaldistancecoveredbytheTECbariscalculated.8 Themeanpointalongthatpathiscalculated.ThispointiscalledtheTECbartangentpoint.9 Theanglethetangentlinetotheorbitatthispointmakeswiththeimaginaryincidentplaneonearthiscalledtheincidentangle.10 NumericalintegrationisperformedonelectrondensityalongtheTECbarorbitaldistance.11 TheresultingvalueistakenastheslantTECatthetangentpoint,theincidentanglebeingcalculatedinpoint9above12. Asmallcorrectionneedstobecarriedouttotrimtheorbitaldistancetoequalthehypotenuseoftheimaginaryrightangledtriangleofaincidentangleandoppositesidedistanceequaltothealtitudeclimbedordescendedbythespacecraftin40seconds(orrelevantTECsubbar).TheTECiscalculatedproportionaltotheratiooforbitaldistanceandhypotenuse13 TheTECvaluesarecalculatedfromcorrectedslantTECsandtheincidentangles.Thepresentationincludesexplanatorydiagramstoillustratethemethodology,theassociatedphysicsandtheproofsforapproximations.TheMagneticStructureofSaturn'sMagnetosheathA.H.Sulaiman,A.Masters,M.K.DoughertyThemagnetosheathistheregionbetweenaplanetarybowshockandmagnetopauseseparatingthehighlysupersonicsolarwindfromtheplanetarymagnetosphere.Withinthisregion,theflowisbeingdeflectedandfieldlinesdrapedanditisanimportantsiteforplasmaturbulence,instabilities,reconnectionandplasmadepletionlayers.Arelativelyhighplasmabeta,highMachnumberregimeandpolarflatteningmakethemagnetosheathofSaturnbothphysicallyandgeometricallydifferentfromtheEarth’s.HereweuseCassinimagneticfielddatatocompareSaturn’smagnetosheathstructurewithbothanalyticalandMHD‐simulatedtreatments.Usingpotentialtheory,thedrapedmagneticfieldacrossabowshockcanbecharacterisedatsteadystatebysolvinganalyticallyandthisgivesanoverestimateofthefield.Astatisticalstudyofmostsheathtraversalsbetween2004and2010showgoodcorrespondenceoftheanalyticallyreconstructedmeridionalangledistributionwiththeIMF,peakingat0o.Thereconstructedspiralanglehowevershowsadoublepeakat~20oand210oatthedawnflankand~150oand~330ofromtheduskflank–significantlydeviatedfromtheparkerspiral.Weanticipateourstudytobeastartingpointformoresophisticatedanalysesonpolarflatteningaswellassheddinglightonphysicalactivitiesinthemagnetosheathdrivenbyitsmagneticstructuresuchasplasmadepletionlayers.
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DensityprofilesofdifferentnegativeionsmassgroupsatTitanobservedbyCassini'sCAPSelectronspectrometerAnneWellbrock,AndrewCoates,GeraintJones,GethynLewis,HunterWaite
ThediscoveryofheavynegativeionsbyCassini’sCAPSelectronspectrometer(ELS)inTitan’sionosphere(Coatesetal,2007,Waiteetal,2007)suggeststhatcomplexhydrocarbonandnitrileprocessesoccurinTitan’supperatmospherewhicharealsolinkedtohazeformation.NegativeionsareobservedduringTitanencountersataltitudes<1400kmandreachmassesupto13,800amu/q(Coatesetal.,2009).RecurringpeaksinthemassspectracanbeusedtoidentifydifferentmassgroupsasreportedbyCoatesetal.(2007).ThesehavebeenupdatedbyWellbrocketal.(2013)whoperformedastudyinvestigatingtrendsofmassgroupswithaltitudeusingdatafrom34negativeionencounters.Wecontinuethisworkherebystudyingindividualflybysinmoredetail.Weinvestigatedensityprofilesfordifferentmassgroupsandtotaldensities.
Jovianthermosphericresponsetomultiplesolarwindshocks
JaphethYates,NicholasAchilleos,LiciaRay,SteveMillerandPatrickGuioRecentworkpresentedinYatesetal2013emphasisedtheimportanceofincorporatingtime‐dependenceinmagnetosphere‐ionosphere‐thermospherecouplingwhensimulatingthisaspectoftheJoviansystem.Weextendtheirmodelbysimulatingtheresponseofthermosphericheatingtomultipleshocksinthesolarwind,byemployingaconfigurablemagnetospheremodelcoupledtoanazimuthallysymmetricgeneralcirculationmodel.WecomparetheensuingresponseofthermospherictemperaturestothesetransientcompressionsandexpansionsoftheJovianmagnetosphereoveraperiodof100Jovianrotations.Wefindthatmeantemperaturegenerallyincreasesthroughoutthesimulation,withamaximumincreaseof~15K.Wealsoshowregionswithabovelocalaveragetemperatures,propagatingfromtheauroralregiontotheequator.
