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  • SH41D-2398 Interstellar Flow Longitude from Pickup Ion Cut ...posters.unh.edu/.../12/10/AGU2015_PUI-CutOff_Poster... · Interstellar Flow Longitude from Pickup Ion Cut-off Observa>ons
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Interstellar Flow Longitude from Pickup Ion Cut-off Observa>ons at 1 AU E. Möbius 1 , M.A. Lee 1 , G. Gloeckler 2 , C. Drews 3 1 Space Science Center & Department of Physics, University of New Hampshire, Durham, NH 03824 e-mail: [email protected] 2 Department of Atmospheric, Oceanic, & Space Sciences, University of Michigan, Ann Arbor, MI, U.S.A. SH41D-2398 Supported by: NASA and DLR • ISN Flow Direc>on from PLASTIC Data 2007-2014: λ ISN∞ = 75.21±0.04 o - Consistent with other observaRons & very small staRsRcal uncertainty à So far only proof of concept: SystemaRc effects must be studied E.g.: V SW , compressions, rarefacRons, B IMF , wave power - Promises very >ght result for λ ISN∞ ßà Synergism with IBEX! • Systema>c Effects evident in 1-Year Data (2007 PLASTIC & SWICS) - Visible as deviaRons from STEREO PLASTIC mulR-year result à RestricRon of V SW & transformaRon reduces effect from ≈10 o to ≈2 o - SystemaRcs randomized across years & longitude (STEREO A & B, ACE) Already successfully applied to Focusing Cone & Crescent [20] • PUI Cut-Off Method uses Newborn Ions à Transport Effects Minimized - Only pitch angle sca‘ering à No effect in solar wind frame • 18+ Year Data Sets (STEREO, ACE & SOHO) for He, O & Ne à Will provide constraints on potenRal Rme variaRons in ISN Flow à Will compare effects of Secondary ISN Component on results and determine Secondary Flow direcRon for O Results & Outlook FIGURE 5: PUI Cut-off as a funcRon of observer longitude λ Obs , obtained from a fit of the respecRve PUI distribuRons in 1 o increments to a hyperbolic tangent with fit uncertainRes, as illustrated in Fig. 4. Normalized counts are used for PLASTIC and PSD for SWICS. Top: STEREO PLASTIC observaRons of the PUI cut-off in the solar wind frame (w’), constrained to V SW < 450 km/s and B IMF so that the torus is completely within the PLASTIC FOV, combining 2007-2014. Center: STEREO PLASTIC observaRons from 2007. Bodom: ACE SWICS observaRons from 2007, constrained in B IMF so that the angle between B IMF and the solar wind is >75 o . Compared with STEREO PLASTIC, the ACE SWICS data are not transformed into the solar wind frame and thus sRll contain a considerable dependence on the B IMF direcRon, as illustrated in Fig. 3. We simply took w’ CutOff = w CutOff – 1. Also shown is the PUI cut-off model curve (in blue, Eq. 1 & 2) assuming λ ISN∞ = 75 o . To account for the effects discussed in Fig. 3, the predicted w’ CutOff values are shiled by ∆w’ = +0.15 for PLASTIC and ∆w’ = -0.2 for SWICS to obtain the best fit. The green arrows and yellow highlight boxes make a connecRon to Fig. 6 and are described below. Introduc>on PUI Cut-Off with STEREO PLASTIC & ACE SWICS PUI Cut-Off Varia>on with Eclip>c Longitude Preliminary ISN Flow Longitude Determina>on The Interstellar Boundary Explorer (IBEX) obtains a very precise relaRon between the interstellar neutral (ISN) flow longitude λ ISN∞ and speed V ISN∞ , with substanRally larger uncertainty separately for λ ISN∞ , which defines a parameter tube that connects ISN longitude, laRtude, speed (velocity vector V ISN∞ ), and temperature [1, 2, 3, 4, 5], in agreement with Ulysses GAS [6, 7, 8] ( Fig. 1 ). The interstellar magneRc field B IS is deduced from the IBEX ribbon, consistent with the heliospheric asymmetry and TeV cosmic ray anisotropy [9]. The two vectors define the B IS - V ISN∞ plane, which determines the shape of, and the flow deflecRon in, the outer heliosheath [10, 11]. An independent determinaRon of λ ISN∞ will Rghten V ISN∞ , and obtaining λ ISN∞ over an extended Rme will resolve a current debate on possible temporal variaRons [12, 13, 14]. • Robust method to obtain λ ISN∞ : Pickup ion (PUI) cut-off speed (high- energy edge of the PUI distribuRon) is a funcRon of the raRo V r /V SW (radial ISN flow component and solar wind speed) [16] As shown in Fig. 2, the cut-off speed in the solar wind frame to a good approximaRon is given by V SW + V r . Normalized to V SW it is then: The cut-off values obtained with PLASTIC are no>ceably higher than model values computed with equaRons (1) and (2) • Model describes ISN bulk flow (center of the torus distribuRon in Fig. 3) - Finite ISN temperature broadens torus à Higher Cut-off - Sensor energy resoluRon broadens torus à Higher Cut-off - Normalized counts: Energy flux density ~ PSD x w 4 à Higher Cut-off • Accumula>on over en>re SWICS FOV in spacecra i frame à Lower cut-off as evident in Fig. 3 . • Same accumula>on procedure for PLASTIC à Also lower cut-off as seen in SWICS and PLASTIC cross-calibraRon spectra [19] • Even small varia>on in B IMF angle Φ B alters the observed cut-off values When taken with ACE SWICS as shown here à Future subdivision by spin angle sectors à Forward modeling of PSD distribuRon for observed V SW , B IMF , etc. will minimize these varia>ons • In the following: - Use PLASTIC normalized count data (observed quanRRes) to test method - Illustrate how individual years with PLASTIC affect results - Illustrate how untransformed data with SWICS affect results References 1. M. Bzowski et al. Astrophys. J. Supp. 220:28 (2015). 2. T. Leonard et al., Astrophys. J. 804:42 (2015). 3. D. J. McComas et al., Astrophys. J. Supp. 220:22 (2015). 3. E. Möbius et al., Astrophys. J. Supp. 220:24 (2015). 4. N.A. Schwadron et al., Astrophys. J. Supp. 220:25 (2015). 6. M. Wi‘e, Astron. & Astrophys. 426, 835 (2004). 7. M. Bzowski et al., Astron. & Astrophys. 569, A8 (2014). 8. B. Wood, H.-R. Mueller & M. Wi‘e, Astrophys. J. 801:62 (2015). 9. N.A. Schwadron et al., Science 343, 988 (2014). 10. R. Lallement et al., Science 307, 1447 (2005). 11. V. Izmodenov, D. Alexashov & A. Myasnikov, Astron. & Astrophys. 437, L35 (2005). 12. P.C. Frisch et al., Science 341, 1080 (2013). 13. P.C. Frisch et al., Astrophys. J. 801:61 (2015). 14. R. Lallement & J.-L. Bertaux, Astron. & Astrophys. 565, A41 (2014). 15. E. Möbius et al., Geophys. Res. Le@. 26, 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. Drews et al. Astron. & Astrophys. 575, 97 (2015). 19. E. Möbius et al., AIP Conf. Proc. 1302, 37 (2010). 20. C. Drews et al., J. Geophys. Res. 117, 9106 (2012). Pickup Ion Cut-Off Modeling •v r is at maximum exactly upwind ( λ Obs = λ Ι SN∞ + 180 o or λ = 0) • v r decreases symmetrically with | λ | • v r = 0: ISN bulk flow reaches 1AU perihelion at λ o [17] (see Fig. 2 ) 3 InsRtut für Experimentelle und Angewandte Physik, ChrisRan-Albrecht-Universität, Kiel, Germany As seen in Fig. 5, the sca‘er of the cut-off values about the best fit model curve increases when using only one year (2007) of PLASTIC data and SWICS data, and for SWICS systemaRc swings appear (two highlighted). To explore the la‘er, we show the variaRon of V SW for the two 2007 data sets with the standard deviaRon of the individual points in Fig. 6. • Pearson correla>on between cut-off values & mirror image about λ M FIGURE 2: SchemaRc view of ISN trajectories with varying angular momenta and resulRng radial V r and tangenRal V θ velocity components at various longitudes λ from upwind [16]. Top: Exactly upwind (right) and where the ISN flow is tangenRal to the Earth’s orbit (lel). Bodom: Arbitrary locaRon between the former two. The insets on the upper lel and right and the lower right show a cut through the resulRng PUI velocity distribuRon in the V SW and B IMF (interplanetary magneRc field) plane in the solar wind frame. Shown is the iniRal torus distribuRon upon injecRon at the combined solar wind and ISN flow velocity for B IMF so that the torus is fully in the STEREO PLASTIC FOV (top right). The dashed circle indicates the edge of the PUI distribuRon for V r = 0. The blow-up in the lower lel shows how the velocity components add up to the maximum PUI speed V Max . r p = 1AU θ ∞ = |λ| V θ = V 0 V r = V 0 Vsw B FoV V sw B r p |λ| θ ∞ θ V r V sw B V Max V sw V 0 B V r FIGURE 3: PUI distribuRon obtained with STEREO PLASTIC in the plane that contains the solar wind and interplanetary magneRc field for φ B = 100 o , in the solar wind frame and subdivided by the dimensionless PUI speed w’ and angle φ (adapted from [18]). Also shown is the full spin-integrated ACE SWICS FOV along with the subdivision in PUI speed w in the spacecral frame. w' w' B B = 100 o φ 0 0 -1 -1 1 1 0.6 0 w' = 1 SWICS FoV W = W'+1 0.012 0.006 -1 -0.5 0 0.5 160 200 240 280 320 λ M λ Upwind = 243.4±1.0 o λ Flow = 63.4±1.0 o ACE SWICS 2007 -1 -0.5 0 0.5 C P (w' Cut-Off ) λ Upwind = 253.13±0.37 o λ Flow = 73.13±0.37 o STEREO PLASTIC 2007 -1 -0.5 0 0.5 1 λ Upwind = 255.21±0.04 o λ Flow = 75.21±0.04 o STEREO PLASTIC 2007-2014 FIGURE 7: Pearson correlaRon coefficient between the measured cut-off values w’ CutOff from Fig. 5 as a funcRon of observer longitude and the same values, mirrored about the longitude λ M , which is incremented in 1 o steps for ±90 o about λ Upwind . Also shown is the best- fit curve to a cosine funcRon, along with the fit values and fit uncertainty for λ Upwind and λ ISN∞ . The verRcal dashed line indicates the upwind direcRon based on the enRre STEREO PLASTIC data set. Top: STEREO PLASTIC observaRons from 2007 through 2014. Center: STEREO PLASTIC observaRons from 2007. Bodom: ACE SWICS observaRons from 2007. The data selecRon is idenRcal to the one used for the cut-off values as a funcRon of observer longitude shown in Fig. 5. FIGURE 1: RelaRonship between V ISN∞ and λ ISN∞ according to the IBEX parameter tube based on various IBEX analyses in comparison with Ulysses results (adapted from [5]). Also shown with a verRcal bar is how an independent measurement of λ ISN∞ will constrain the ISN flow vector. The effect of a precise independent determinaRon of the ISN flow longitude λ ISN∞ on the knowledge of the ISN flow parameters is indicated by the green verRcal bar. 70 80 78 76 74 72 o 30 28 26 22 24 V ISN∞ [km/s] λ ISN∞ [ o ] v r 2 = 2 + v ISN ∞ 2 − (1 − cos λ ) − v ISN ∞ 2 sin 2 λ + v ISN ∞ sin | λ |[ v ISN ∞ 2 sin 2 λ + 4(1 − cos λ )] 1/2 { } /2 • Radial ISN flow v r = V r / V E (normalized to Earth’s speed) varies with λ [16] cos λ 0 = – (1 + v ISN ∞ 2 ) −1 (1) w ' CutOff = ( V SW + V r )/ V SW PUI distribuRons are gyrotropic and mostly sca‘er in pitch angle. As shown recently [18], they largely maintain their iniRal torus distribuRon with some sca‘ering, which introduces a Φ B dependent w CutOff bias in the rest frame. Fig. 3 shows a distribuRon obtained with PLASTIC aler transformaRon into the solar wind frame (w’) in the B IMF -V SW plane. AccumulaRon along shells in constant w’ produces a cut-off that does not depend on the B IMF angle. • Cut-off speed only minimally affected by PUI transport effects Produced by newborn ions and not altered by pitch angle sca‘ering (2) • SWICS and PLASTIC phase space densi>es (PSD) and PLASTIC normalized counts in w’ across the cut-off are shown in Fig. 4 (with data used for PLASTIC and SWICS cross-calibraRon [19]) Figure 4: PUI spectra near the cut- off in the upwind direcRon (251 o < λ Obs < 260 o ) and staRsRcal uncertainRes. The PLASTIC spectra (normalized counts in red and normalized PSD in black) are accumulated on circles of constant w’ (black circle in Fig. 3) and the SWICS spectrum on constant w (magenta arcs in Fig. 3). Also shown are fits to a hyperbolic tangent, the inflecRon points (horizontal dashed line), and the model value of w’ CutOff (solid blue line) for λ Obs = 255 o with the standard deviaRon of the observed cut-off values (dashed blue lines). 0 0.2 0.4 0.6 0.8 1 Normalized Counts 0.5 1 1.5 w' PLASTIC Cts λ Obs : 251 o - 260 o SWICS PSD w' CutOff = 1.287 ± 0.002 w' CutOff = 1.229 ± 0.003 w' CutOff = 1.02 ± 0.07 PLASTIC PSD /PSD • Use of PUI Cut-Off obtained as shown in Fig. 4 as a func>on of λ Obs • With no restric>ons in V SW for SWICS, V SW in Fig. 6 is almost bi-modal à ParRally reflected in cut-off values in Fig. 5 • Huge V SW swings coincide with cut-off swings (highlighted in Fig. 5&6) • PLASTIC shows less systema>c varia>ons, but some visible outliers à Coincide with transiRons to cut-out high V SW (verRcal green lines) • V SW varia>ons oien connected to solar wind compressions à Such systemaRc effects must be studied in detail • Systema>c varia>ons occur stochas>cally across years à Influence can be miRgated in mulR-year/longitude combinaRons [20] 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 0 90 180 270 360 ACE SWICS 2007 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 w' Cut-Off STEREO PLASTIC 2007 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 STEREO PLASTIC 2007-2014 λ Obs [ o ] FIGURE 6: Solar wind speed as a funcRon of eclipRc longitude, including its standard deviaRon for 1 o samples over the year 2007. Top: Averaged for the STEREO PLASTIC PUI data selecRon: - V SW < 450 km/s - Only Rmes taken with IMF direcRon so that the PUI torus distribuRon is completely within the PLASTIC FOV • The verRcal green lines point to the start of a gap due to the V SW restricRon. They coincide in λ Obs with the green arrows in Fig. 5, which point to PUI Cut-Off outliers. Bodom: Averaged for the ACE SWICS PUI data selecRon: - Only Rmes taken with IMF direcRon so that θ BVsw > 75 o • The highlight boxes indicate large V SW swings, which coincide with large systemaRc variaRons in the cut-off values in Fig. 5. 250 300 350 400 450 500 StereoPl_2007_PUI_90_wCut 200 300 400 500 600 700 800 0 90 180 270 360 ACE-SWICS_2007_PUI_BV>75 o V SW [km/s] o λ Obs [ o ]

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Page 1: SH41D-2398 Interstellar Flow Longitude from Pickup Ion Cut ...posters.unh.edu/.../12/10/AGU2015_PUI-CutOff_Poster... · Interstellar Flow Longitude from Pickup Ion Cut-off Observa>ons

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.

rp = 1AU

θ∞ = |λ|

Vθ = V0

Vr = V0

Vsw

B

FoV

Vsw

B

rp |λ|

θ∞

θVr

Vsw B

VMax

Vsw

V0

B

Vr

FIGURE3:PUIdistribuRonobtainedwithSTEREOPLASTICintheplanethatcontainsthesolarwindandinterplanetarymagneRcfieldfor φB= 100o,inthesolarwindframeandsubdividedbythedimensionlessPUIspeedw’andangleφ (adaptedfrom[18]).Alsoshownisthefullspin-integratedACESWICSFOValongwiththesubdivisioninPUIspeedwinthespacecralframe.

w'

w'

B

BB = 100oφ

0

0

-1

-1

1

1

1.2.10-2

0.6.10-2

0

w' = 1SWICS FoV

W = W'+1

0.012

0.006

-1

-0.5

0

0.5

1

160 200 240 280 320λ

M

λUpwind

= 243.4±1.0o

λFlow

= 63.4±1.0o

y = m1*cos(m2*(x-m3))ErrorValue

0.00892910.2564m1 0.0404671.9621m2

0.9778243.41m3 NA1.19ChisqNA0.91135R

ACE SWICS 2007-1

-0.5

0

0.5

1

CP(w

' Cut

-Off)

λUpwind

= 253.13±0.37o

λFlow

= 73.13±0.37o

y = m1*cos(m2*(x-m3))ErrorValue

0.00555110.40744m1 0.0162151.9935m2 0.37252253.13m3

NA0.4457ChisqNA0.98536R

STEREO PLASTIC 2007-1

-0.5

0

0.5

1

λUpwind

= 255.21±0.04o

λFlow

= 75.21±0.04o

y = m1*cos(m2*(x-m3))ErrorValue

0.00121840.86927m1 0.00169032.0068m2 0.038335255.21m3

NA0.021627ChisqNA0.99984R

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.

70 8078767472λISN∞ [

o]

30

28

26

22

24

VISN

∞ [km/s]

λISN∞[o]

vr2 = 2+ vISN∞2 − (1− cosλ)− vISN∞2 sin2 λ + vISN∞ sin | λ | [vISN∞2 sin2 λ + 4(1− cosλ)]1/2{ } / 2•RadialISNflowvr=Vr/VE(normalizedtoEarth’sspeed)varieswithλ[16]

cosλ0 = – (1 + vISN∞2 )−1

(1)

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).

0

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Norm

aliz

ed C

ount

s

0.5 1 1.5w'

PLASTIC Cts

λObs

: 251o - 260o

SWICS PSD

w'CutOff

= 1.287 ± 0.002

w'CutOff

= 1.229 ± 0.003

w'CutOff

= 1.02 ± 0.07

PLASTIC PSD

/PSD

•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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[o]

ACE SWICS 20070.8

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STEREO PLASTIC 20070.8

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1.6STEREO PLASTIC 2007-2014

λObs [o]

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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ACE-SWICS_2007_PUI_BV>75o

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