InterstellarFlowLongitudefromPickupIonCut-offObserva>onsat1AUE.Möbius1,M.A.Lee1,G.Gloeckler2,C.Drews31SpaceScienceCenter&DepartmentofPhysics,UniversityofNewHampshire,Durham,NH03824e-mail:[email protected],Oceanic,&SpaceSciences,UniversityofMichigan,AnnArbor,MI,U.S.A.
SH41D-2398
Supportedby:NASAandDLR
•ISNFlowDirec>onfromPLASTICData2007-2014:λISN∞=75.21±0.04o-ConsistentwithotherobservaRons&verysmallstaRsRcaluncertaintyàSofaronlyproofofconcept:SystemaRceffectsmustbestudiedE.g.:VSW,compressions,rarefacRons,BIMF,wavepower-Promisesvery>ghtresultforλISN∞ßàSynergismwithIBEX!
•Systema>cEffectsevidentin1-YearData(2007PLASTIC&SWICS)-VisibleasdeviaRonsfromSTEREOPLASTICmulR-yearresultàRestricRonofVSW&transformaRonreduceseffectfrom≈10oto≈2o-SystemaRcsrandomizedacrossyears&longitude(STEREOA&B,ACE)AlreadysuccessfullyappliedtoFocusingCone&Crescent[20]•PUICut-OffMethodusesNewbornIonsàTransportEffectsMinimized-Onlypitchanglesca`eringàNoeffectinsolarwindframe•18+YearDataSets(STEREO,ACE&SOHO)forHe,O&NeàWillprovideconstraintsonpotenRalRmevariaRonsinISNFlowàWillcompareeffectsofSecondaryISNComponentonresultsanddetermineSecondaryFlowdirecRonforO
Results&Outlook
FIGURE5:PUICut-offasafuncRonofobserverlongitudeλObs,obtainedfromafitoftherespecRvePUIdistribuRonsin1oincrementstoahyperbolictangentwithfituncertainRes,asillustratedinFig.4.NormalizedcountsareusedforPLASTICandPSDforSWICS.Top:STEREOPLASTICobservaRonsofthePUIcut-offinthesolarwindframe(w’),constrainedtoVSW<450km/sandBIMFsothatthetorusiscompletelywithinthePLASTICFOV,combining2007-2014.Center:STEREOPLASTICobservaRonsfrom2007.Bodom:ACESWICSobservaRonsfrom2007,constrainedinBIMFsothattheanglebetweenBIMFandthesolarwindis>75o.ComparedwithSTEREOPLASTIC,theACESWICSdataarenottransformedintothesolarwindframeandthussRllcontainaconsiderabledependenceontheBIMFdirecRon,asillustratedinFig.3.Wesimplytookw’CutOff=wCutOff–1.AlsoshownisthePUIcut-offmodelcurve(inblue,Eq.1&2)assumingλISN∞=75o.ToaccountfortheeffectsdiscussedinFig.3,thepredictedw’CutOffvaluesareshiledby∆w’=+0.15forPLASTICand∆w’=-0.2forSWICStoobtainthebestfit.ThegreenarrowsandyellowhighlightboxesmakeaconnecRontoFig.6andaredescribedbelow.
Introduc>on PUICut-OffwithSTEREOPLASTIC&ACESWICS PUICut-OffVaria>onwithEclip>cLongitude PreliminaryISNFlowLongitudeDetermina>onTheInterstellarBoundaryExplorer(IBEX)obtainsaverypreciserelaRonbetweentheinterstellarneutral(ISN)flowlongitudeλISN∞andspeedVISN∞,withsubstanRallylargeruncertaintyseparatelyforλISN∞,whichdefinesaparametertubethatconnectsISNlongitude,laRtude,speed(velocityvectorVISN∞),andtemperature[1,2,3,4,5],inagreementwithUlyssesGAS[6,7,8](Fig.1).TheinterstellarmagneRcfieldBISisdeducedfromtheIBEXribbon,consistentwiththeheliosphericasymmetryandTeVcosmicrayanisotropy[9].ThetwovectorsdefinetheBIS-VISN∞plane,whichdeterminestheshapeof,andtheflowdeflecRonin,theouterheliosheath[10,11].AnindependentdeterminaRonofλISN∞willRghtenVISN∞,andobtainingλISN∞overanextendedRmewillresolveacurrentdebateonpossibletemporalvariaRons[12,13,14].
•RobustmethodtoobtainλISN∞:Pickupion(PUI)cut-offspeed(high-energyedgeofthePUIdistribuRon)isafuncRonoftheraRoVr/VSW(radialISNflowcomponentandsolarwindspeed)[16]
AsshowninFig.2,thecut-offspeedinthesolarwindframetoagoodapproximaRonisgivenbyVSW+Vr.NormalizedtoVSWitisthen:
Thecut-offvaluesobtainedwithPLASTICareno>ceablyhigherthanmodelvaluescomputedwithequaRons(1)and(2)•ModeldescribesISNbulkflow(centerofthetorusdistribuRoninFig.3)-FiniteISNtemperaturebroadenstorusàHigherCut-off-SensorenergyresoluRonbroadenstorusàHigherCut-off-Normalizedcounts:Energyfluxdensity~PSDxw4àHigherCut-off•Accumula>onoveren>reSWICSFOVinspacecraiframeàLowercut-offasevidentinFig.3.•Sameaccumula>onprocedureforPLASTICàAlsolowercut-offasseeninSWICSandPLASTICcross-calibraRonspectra[19]•Evensmallvaria>oninBIMFangleΦBalterstheobservedcut-offvaluesWhentakenwithACESWICSasshownhereàFuturesubdivisionbyspinanglesectorsàForwardmodelingofPSDdistribuRonforobservedVSW,BIMF,etc.willminimizethesevaria>ons•Inthefollowing:-UsePLASTICnormalizedcountdata(observedquanRRes)totestmethod-IllustratehowindividualyearswithPLASTICaffectresults-IllustratehowuntransformeddatawithSWICSaffectresults
References1. M.Bzowskietal.Astrophys.J.Supp.220:28(2015).2. T.Leonardetal.,Astrophys.J.804:42(2015).3. D.J.McComasetal.,Astrophys.J.Supp.220:22(2015).3. E.Möbiusetal.,Astrophys.J.Supp.220:24(2015).4. N.A.Schwadronetal.,Astrophys.J.Supp.220:25(2015).6. M.Wi`e,Astron.&Astrophys.426,835(2004).7. M.Bzowskietal.,Astron.&Astrophys.569,A8(2014).8. B.Wood,H.-R.Mueller&M.Wi`e,Astrophys.J.801:62(2015).9. N.A.Schwadronetal.,Science343,988(2014).10. R.Lallementetal.,Science307,1447(2005).11. V.Izmodenov,D.Alexashov&A.Myasnikov,Astron.&Astrophys.437,L35(2005).12.P.C.Frischetal.,Science341,1080(2013).13. P.C.Frischetal.,Astrophys.J.801:61(2015).14. R.Lallement&J.-L.Bertaux,Astron.&Astrophys.565,A41(2014).15. E.Möbiusetal.,[email protected],3181(1999).16. E.Möbius,M.A.Lee&C.Drews,Astrophys.J.,815:20(2015).17. M.A.Lee,E.Möbius&T.Leonard,Astrophys.J.Supp.220:23(2015).18. C.Drewsetal.Astron.&Astrophys.575,97(2015).19. E.Möbiusetal.,AIPConf.Proc.1302,37(2010).20. C.Drewsetal.,J.Geophys.Res.117,9106(2012).
PickupIonCut-OffModeling
•vrisatmaximumexactlyupwind(λObs=λΙSN∞+180oorλ=0)•vrdecreasessymmetricallywith|λ|•vr=0:ISNbulkflowreaches1AUperihelionatλo[17](seeFig.2)
3InsRtutfürExperimentelleundAngewandtePhysik,ChrisRan-Albrecht-Universität,Kiel,Germany
AsseeninFig.5,thesca`erofthecut-offvaluesaboutthebestfitmodelcurveincreaseswhenusingonlyoneyear(2007)ofPLASTICdataandSWICSdata,andforSWICSsystemaRcswingsappear(twohighlighted).Toexplorethela`er,weshowthevariaRonofVSWforthetwo2007datasetswiththestandarddeviaRonoftheindividualpointsinFig.6.
•Pearsoncorrela>onbetweencut-offvalues&mirrorimageaboutλM
FIGURE2:SchemaRcviewofISNtrajectorieswithvaryingangularmomentaandresulRngradialVrandtangenRalVθvelocitycomponentsatvariouslongitudesλfromupwind[16].Top:Exactlyupwind(right)andwheretheISNflowistangenRaltotheEarth’sorbit(lel).Bodom:ArbitrarylocaRonbetweentheformertwo.TheinsetsontheupperlelandrightandthelowerrightshowacutthroughtheresulRngPUIvelocitydistribuRonintheVSWandBIMF(interplanetarymagneRcfield)planeinthesolarwindframe.ShownistheiniRaltorusdistribuRonuponinjecRonatthecombinedsolarwindandISNflowvelocityforBIMFsothatthetorusisfullyintheSTEREOPLASTICFOV(topright).ThedashedcircleindicatestheedgeofthePUIdistribuRonforVr=0.Theblow-upinthelowerlelshowshowthevelocitycomponentsadduptothemaximumPUIspeedVMax.
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FIGURE3:PUIdistribuRonobtainedwithSTEREOPLASTICintheplanethatcontainsthesolarwindandinterplanetarymagneRcfieldfor φB= 100o,inthesolarwindframeandsubdividedbythedimensionlessPUIspeedw’andangleφ (adaptedfrom[18]).Alsoshownisthefullspin-integratedACESWICSFOValongwiththesubdivisioninPUIspeedwinthespacecralframe.
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STEREO PLASTIC 2007-2014FIGURE7:PearsoncorrelaRoncoefficientbetweenthemeasuredcut-offvaluesw’CutOfffromFig.5asafuncRonofobserverlongitudeandthesamevalues,mirroredaboutthelongitude λM,whichisincrementedin1ostepsfor±90oaboutλUpwind.Alsoshownisthebest-fitcurvetoacosinefuncRon,alongwiththefitvaluesandfituncertaintyfor λUpwindandλISN∞.TheverRcaldashedlineindicatestheupwinddirecRonbasedontheenRreSTEREOPLASTICdataset.Top:STEREOPLASTICobservaRonsfrom2007through2014.Center:STEREOPLASTICobservaRonsfrom2007.Bodom:ACESWICSobservaRonsfrom2007.ThedataselecRonisidenRcaltotheoneusedforthecut-offvaluesasafuncRonofobserverlongitudeshowninFig.5.
FIGURE1:RelaRonshipbetweenVISN∞andλISN∞accordingtotheIBEXparametertubebasedonvariousIBEXanalysesincomparisonwithUlyssesresults(adaptedfrom[5]).AlsoshownwithaverRcalbarishowanindependentmeasurementofλISN∞willconstraintheISNflowvector.TheeffectofapreciseindependentdeterminaRonoftheISNflowlongitudeλISN∞ontheknowledgeoftheISNflowparametersisindicatedbythegreenverRcalbar.
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w 'CutOff = (VSW +Vr ) /VSWPUIdistribuRonsaregyrotropicandmostlysca`erinpitchangle.Asshownrecently[18],theylargelymaintaintheiriniRaltorusdistribuRonwithsomesca`ering,whichintroducesaΦBdependentwCutOffbiasintherestframe.Fig.3showsadistribuRonobtainedwithPLASTICalertransformaRonintothesolarwindframe(w’)intheBIMF-VSWplane.AccumulaRonalongshellsinconstantw’producesacut-offthatdoesnotdependontheBIMFangle.•Cut-offspeedonlyminimallyaffectedbyPUItransporteffectsProducedbynewbornionsandnotalteredbypitchanglesca`ering
(2)
•SWICSandPLASTICphasespacedensi>es(PSD)andPLASTICnormalizedcountsinw’acrossthecut-offareshowninFig.4(withdatausedforPLASTICandSWICScross-calibraRon[19])
Figure4:PUIspectranearthecut-offintheupwinddirecRon(251o<λObs<260o)andstaRsRcaluncertainRes.ThePLASTICspectra(normalizedcountsinredandnormalizedPSDinblack)areaccumulatedoncirclesofconstantw’(blackcircleinFig.3)andtheSWICSspectrumonconstantw(magentaarcsinFig.3).Alsoshownarefitstoahyperbolictangent,theinflecRonpoints(horizontaldashedline),andthemodelvalueofw’CutOff(solidblueline)for λObs=255owiththestandarddeviaRonoftheobservedcut-offvalues(dashedbluelines).
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•UseofPUICut-OffobtainedasshowninFig.4asafunc>onofλObs
•Withnorestric>onsinVSWforSWICS,VSWinFig.6isalmostbi-modalàParRallyreflectedincut-offvaluesinFig.5•HugeVSWswingscoincidewithcut-offswings(highlightedinFig.5&6)•PLASTICshowslesssystema>cvaria>ons,butsomevisibleoutliersàCoincidewithtransiRonstocut-outhighVSW(verRcalgreenlines)•VSWvaria>onsoienconnectedtosolarwindcompressionsàSuchsystemaRceffectsmustbestudiedindetail•Systema>cvaria>onsoccurstochas>callyacrossyearsàInfluencecanbemiRgatedinmulR-year/longitudecombinaRons[20]
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FIGURE6:SolarwindspeedasafuncRonofeclipRclongitude,includingitsstandarddeviaRonfor1osamplesovertheyear2007.Top:AveragedfortheSTEREOPLASTICPUIdataselecRon:-VSW<450km/s-OnlyRmestakenwithIMFdirecRonsothatthePUItorusdistribuRoniscompletelywithinthePLASTICFOV•TheverRcalgreenlinespointtothestartofagapduetotheVSWrestricRon.TheycoincideinλObswiththegreenarrowsinFig.5,whichpointtoPUICut-Offoutliers.Bodom:AveragedfortheACESWICSPUIdataselecRon:-OnlyRmestakenwithIMFdirecRonsothatθBVsw>75o•ThehighlightboxesindicatelargeVSWswings,whichcoincidewithlargesystemaRcvariaRonsinthecut-offvaluesinFig.5.
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