Studies of laminar shocks based on ISEE observations of terrestrial bow shocks, simulation, and theory are presented

Aldrich, C. H.

Bame, S. J.

Forslund, D. W.

Gary, S. P.

Gosling, J. T.

Lee, K.

Mellott, M. M.

Quest, K. B.

Thomsen, M. F.

Winske, D.

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calthebleA major purpose of the Techni-Information Center is to providebroadest dissemination possi-of informationDOE’s Research andReports to business,academic community,contained inDevelopmentindustry, theand federal,state and local governments.Although a small portion of thisreport is not reproducible, it isbeing made available to expeditethe availability of information on theresearch discussed herein.NullLt~A-lJR -84-892‘~RTIoNs OF THIS REPORT ARE ILLEGIBLL itllJs-be~;d~j~~~~-fh<-b~~~-copytopormlt tit. bmdm poulbh roll=zoility.LOS AIamoI NMon@l Laboratory Is o~rated by the Unlvomlly of California for tho UnllOd Slaloo ~fim.nt of Energy under COnIr~Cl W-7405 -ENG.36TITLE: INVESTIGATION OF LAMINAR SHOCKSAUT’ !OR(S): K. Lee, C. H. Aldrich,S. J. Bame,D. W. Forslund,S. P. Gary,J. T. Gosling,K. B. Quest,M. F. Thomsen,D. Wlnske,& M. M. MellottSUBMITTED TO: Proceedingsof the 1984 InternationalConferenceon PlasmaPhysics,bausanne,Switzerland,J’me 27-July3, 1984I)IS(”I,AIMI?RThis rcpm wwiprcprd IISIIII nccount ofw{mk sponw.rcd hymu u~cncyof [he U-ikd Stutcn(iovernmcm. Neither !hc I lnmxl SI:, IIX (iovcrrm, cnlnor uny ugrncy thmcof, nur my of theircmployccs, mukcs IIIIy wulrun!y, ~lprck or i,llplicd, t,r mwumcs MI) Icgul Iiahility or rcsponni-hilily I’m Ihc IIWJI ,Icy, wmph (cncss, (w uscllllntsh 11(my inhrmwlion, opfmrnlun, producl, orprovcm disclnscd, w 1,.presents [hut its IIW W{IUM no! inl’ringc privutcly nwncd rigirla, Refcr-cncc herein tonny Hpxific uommcrciul produc[, prmx.s. m wrvim hy Irndc ntimc, Irndcmark,mnnufncturer, nr .’~hcrwisc IIIICS nol ncm.murily constitute w imply IIH cmlnrncmcnt, rctom.mcnduiion, or ruvorin~ IIV Ihc [Ini[cd SIIIICS (i(wcrnmc!t: nr wny nNcncy Ihcrcof’. ‘The vicwnund upinionn of mlthors cxprcwcd hcrwn du nol ncuwsurily SIHIC or rcflccl thmc of the(Jnilcd Stnics(iovcrnillcnlt )r: i!;,, ugcnuythcrcof,Byaccoplancooflhln ,r!,~lo, lho Dubllahor rWqnlloI ll\allho U5.00tiarnmonlr alalnsa nonaxcluslvo,r oyally-lrMl lconsol opubllshn rr@producatl?opubll@hM form of tMI comlbuuon, 01 10 ●now olhorn 10 do 10, for U.B OovornmonlpurposaTM Loo AlamoI N#unnal Iabomlov rquos,l Ilml !ho publlshor Idontlfy Ihlm arllcla as Mrhp@rfWmod undorlhe -uIplcasoflho US Ooparlmonlot EndrgyLosAkallinmLos Alamos National LaboratoryLos Alamos,fVew Mexico 87545FOnM NO WC FM0! No ?otsefslmm9ullllN N ml D(ICUM!HIISunlltillfnbINVESTIGATIONOF LAMINARSHOCKSK. Ice, C. H. Aldrich,S. ,T.Bme, D. W. Forslund,S. P. Gary,J. T. Gosling,K. B. Quest,M. F. Thomsen,D. WinskeIas AlamosNationslLaboratorybS AhJ.IIOS, NM87545 USAu. ofAbstract: StudiesofM. M. MellottIowa,IowaCity,IA 52242USAleminarshocksbasedon ISEE observationsofterrestrialbow shocks,simulation,and theoryare presented.1. Observations—We report several investigationssho~ks,motivatedby him time resolutiondistributionsacrosa quasiperpendicularof subcritical(laminar)dataof electronand ionterrestrialbow shocksfrom the ISE&l and 2 spacecraft.1-3Contraryto the conventionalwisdom that at subcritical shocks the hulk of the energydimipation occursas reaiative heating of the electrons, theobservationsshow that the ion temperatureincreaseexceedsthatof the eiectrons. The increase in the ion temperature istypicallv a factor of 10-20,predominantlyin the perpendiculardirection,and due to heatingof the entire distributionratherthan the formation of a high energy tail. The electrontemperatureincreasesYy only a f~ctorof abouttwo, equnlto thntof the magnetic field jump,and remainsfairly~sotropic,whilethe dowmtream electroi~distributionexhibits the characteristicflat top seenalso at supercriticalshocks. An exampleof suchRlaminarshock Is gj’venin Fig. 1, which shows the plwm]pare!neterprofilerfor the shockcrossingat 2105 UT on 27 A~mt1978.3Plottedare the lo~rithnw of the dmoity (solidcurvefromelectron measurements,tJymuoLafrom the ionmeasurements)nnd themaximumand minimumve.lueain the dingonallzedion and e19ctrontemperaturematriceo. The verticnllinenindlcntethe locntionof,.-2-the ramp in the ma@etic field profile. The upstresm ionmeasurementswere made with the ISE&l solarwind ion instrument;all othermeasurementswere obtainedwith the ISE&2 R& PlasmaExperiment. In this case the electrontemperatureincreaseacrossthe shockis a factorof 2.5,whilethe ion temperature increaseis 10.& SimulationsThese o?)servationsare interpretedas evidence for thepossibleoperationof variousplasmainstabilitiesin the shockleyer, which are being investigatedby means of computersimulation. To study the effect of short wavelength (ionacoustic) modes,simulationswith the explicitparticlecodeWAVEhavebeen initiated. The simulationsare initializedwith uniformupstream and downstream stat~sconsistentwith Rankine-Hugoniotrelations,with plasma continuouslyinjected at one end tomaintain ‘he shock. One-dimensionalcalculationsshow that astationarystatecan be maintainedfor long ~riods of time inthis manner. In this case cross-fieldinstabilitie~cannotbeex~ited, smd the shock forms by reflecting some ionE.Twdimensional calculationsare in profress. In orderto studythe effectsof longer wavelength, lower hybrid (modified twostreemand lowerhybriddrift)instability{’”,sirmllationswith theimplicitparticlecodeVENUShavealsobeen conducted,similar toprevious celculationcfor auperc-’iticalshocks.4 1.owever,suchlowerhybridinstabilities(ionacousticmodesere not resclvetijare not ~tronfllyexcited;rather,a SW1l ~(lii)lt of’ ion reflectionoccure. In this case the shock is createdby the piston, whichmay be flivi~,some extradissipationin the downstre,nmre,qion,> TheoryThe dempin~ of whistler:]ohnerved an precursors~tnnilin~;upntrenmof laminarshockshas alsc been addressed,5 ]~fln”lt~ ~j’ (,linenr Vhu+ov unn.lyL~imchow thmt electron IAndm dnmpin~c:m-3attenuate obliquewhistlerswith dampinglengthsthat are the sameorder of ~itude as thoseobserved. Fi~re 2 showsan exampleof such calculations,the ratioof dampingrate to real frequency(y/wr) ss a function ofpro~tion~e for one V~U of thewavevector (kc/ui=5.0). The fi~re indicatesthatthe determining~ter is the electron bsta {fle),that the relativerateofdampingincreasesdefinite~ ofhere).L&E!!?!Zwith Be, and that ly~/~ is maximum over aO (ro@ly 5@ < 0 < @ for the parametersusedWe have presented results of various studies of lsminarshocks: an analysis of ISEE observationsvhichshow strongIonheatingof subcriticalterrestrialbow shocks,preliminaryresultsof particle simulationsto understandthe microscopicprocesssswhichgivedampingofReferencesriseto such heating,whistler precursors.1.2.3949q.C. T.S. J.M. M.pressM. F.and theory which explains t}leW. A. Livesey, J. T. Gos1:v., andRussell, M. M. HOW,Bame, Geophys. Res. I&t. ~y 1171 (1982).Mellottend 3. W. Greenstsdt, J. Geophys. Res. *, in(lW).Thomen, J. T. Gosliqg, S. J. Bame, sndll. M. Mellott, J.Geophys. Res.,D. W. Foralund,Geophys. Res.,S. P. Gary and:Iw).Sutmlitted (Igst$).K. B. Quesf, J. U. Brackbill, and K. Tee, J.89, Irl press (1984).-M. M. Mellott, J. Geophye. Res., subm!tted.‘-4--0.0-0.0FIGURE1-O,O~cLG._.’ 1 I t 1 I 120“ 40” 60” 800QFIGURE2

Investigation of laminar shocks

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Investigation of laminar shocks

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