Fluid Models for Kinetic Effects on Coherent Nonlinear Alfven Waves. II. Numerical Solution

The influence of various kinetic effects (e.g. Landau damping, diffusive and collisional dissipation, and finite Larmor radius terms) on the nonlinear evolution of finite amplitude Alfvenic wave trains in a finite-beta environment is systematically investi

FluidModelsforKineticE ectsonCoherentNonlinearAlfv´enWaves.II.Numerical

Solutions

PhysicsDepartment,UniversityofCaliforniaatSanDiego,LaJolla,California92093-0319

Electrical&ComputerEngineeringDepartment,UniversityofCaliforniaatSanDiego,LaJolla,California92093-0407

3

ScrippsInstitutionofOceanography,UniversityofCaliforniaatSanDiego,LaJolla,California92093-0210

Thein uenceofvariouskinetice ects(http://www.wendangwang.comndaudamping,di usiveandcollisionaldissipation,and niteLarmorradiusterms)onthenonlinearevolutionof niteamplitudeAlfv´enicwavetrainsina nite-βenvironmentissystematicallyinvestigatedusinganovel,kineticnonlinearSchr¨odinger(KNLS)equation.ThedynamicsofAlfv´enwavesissensitivetothesenseofpolarizationaswellastheangleofpropagationwithrespecttotheambientmagnetic eld.NumericalsolutionforthecasewithLandaudampingrevealstheformationofdissipativestructures,whicharequasi-stationary,S-polarizeddirectional(androtational)discontinuitieswhichself-organizefromparallelpropagating,linearlypolarizedwaves.ParallelpropagatingcircularlypolarizedpacketsevolvetoafewcircularlypolarizedAlfv´enharmonicsonlargescales.Stationaryarc-polarizedrotationaldiscontinuitiesformfromobliquelypropagatingwaves.Collisionaldissipation,evenifweak,introducesenhancedwavedampingwhenβisveryclosetounity.Cyclotronmotione ectsonresonantparticleinteractionsintroducecyclotronresonanceintothenonlinearAlfv´enwavedynamics.PACSnumbers:96.50.Ci,52.35.Mw,52.35.-g,95.30.Qd

1

M.V.Medvedev1,

,

,V.I.Shevchenko2,P.H.Diamond1,

,andV.L.Galinsky3

2

arXiv:physics/9612018v1 [physics.plasm-ph] 31 Dec 1996

I.INTRODUCTION

TheenvelopedynamicsofnonlinearAlfv´enwavesatsmall-βarethoughttobegovernedbythederivativenonlinearSchr¨odinger(DNLS)equation,whichdescribesparametriccouplingwithacousticmodes[1].Itisbe-lievedthatthedynamicsofsuchwaveschangesdrasti-callyinacollisionless, nite-βplasma,duetoseveralkinetice ects,especiallycollisionless(Landau)damp-ingofion-acousticoscillations[2–4].Inahighlydissi-pativeregime,theion-acousticquasi-modeisnolongeraplasmaeigenmode.Thus,itismorenatural(accord-ingRefs.[5,6])toviewthemechanismofLandaudamp-ingofAlfv´enwavesasparticletrappingbyboththemagneticmirrorforceandelectric eld.Onaccountoftheinevitablemathematicaldi cultiesofakineticapproach,manynumericalsimulationshavebeenper-formed.DNLS-basedsimulationswithbeampumping(cometmodeling)[7,8],hybridmagnetohydrodynamic-particlesimulations[9,10],hybridparticleions- uidelec-tronssimulations[11–13]havebeenperformed.

Inapreviouspaper[14],wesystematicallyaccountedforionkinetice ects(butneglected niteconductiv-ity,discussedelsewhere[3,15])onparallelandslightlyobliquepropagatingwavesinhomogeneousplasma,totheorderatwhichtheDNLSisderived.A uidrepre-sentationforLandaudamping[16]allowedustoderivea

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