Physics of Space Storms: From the Solar Surface to the Earth

431 Pages·2011·6.591 MB·English

by  Hannu Koskinen (auth.)

Physics of Space Storms
FromtheSolarSurfacetotheEarth

Hannu E. J. Koskinen
Physics of Space Storms
From the Solar Surface to the Earth
Published inassociationwith
PPrraaxxiiss PPuubblliisshhiinngg
Chichester, UK
Professor Hannu E. J. Koskinen
University of Helsinki and Finnish Meteorological Institute
Helsinki
Finland
SPRINGER–PRAXISBOOKSINENVIRONMENTALSCIENCES
SUBJECTADVISORYEDITOR:JohnMason,M.B.E.,B.Sc.,M.Sc.,Ph.D.
ISBN 978-3-642-00310-3 e-ISBN 978-3-642-00319-6
DOI 10.1007/978-3-642-00319-6
Springer Heidelberg Dordrecht London New York
Library of Congress Control Number: 2010934386
# Springer-Verlag Berlin Heidelberg 2011
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Contents
Preface................................................................. XI
Acknowledgements ...................................................... XV
1. StormyTourfromtheSuntotheEarth................................ 1
1.1 SourceofSpaceStorms:theSun................................... 1
1.1.1 TheSunasastar.......................................... 2
1.1.2 Solarspectrum ........................................... 5
1.1.3 Solaratmosphere ......................................... 7
1.1.4 RotationoftheSun........................................ 8
1.1.5 Sunspotsandsolarmagnetism .............................. 11
1.1.6 Coronalactivity .......................................... 16
1.2 TheCarriertotheEarth:theSolarWind ............................ 21
1.2.1 Elementsofsolarwindexpansion ........................... 21
1.2.2 Theinterplanetarymagneticfield............................ 25
1.2.3 Theobservedstructureofthesolarwind...................... 28
1.2.4 Perturbedsolarwind ...................................... 29
1.3 TheMagnetosphere.............................................. 32
1.3.1 FormationoftheEarth’smagnetosphere ...................... 32
1.3.2 Theoutermagnetosphere................................... 34
1.3.3 Theinnermagnetosphere................................... 37
1.3.4 Magnetosphericconvection................................. 40
1.3.5 Originsofmagnetosphericplasma ........................... 44
1.3.6 Convectionandelectricfields ............................... 45
1.4 TheUpperAtmosphereandtheIonosphere.......................... 48
1.4.1 Thethermosphereandtheexosphere ......................... 49
1.4.2 Structureoftheionosphere ................................. 50
1.4.3 Electriccurrentsinthepolarionosphere ...................... 51
1.5 SpaceStormsSeenfromtheGround................................ 54
1.5.1 Measuringthestrengthofspacestorms....................... 55
1.5.2 Geomagneticallyinducedcurrents ........................... 57
VI Contents
2. PhysicalFoundations ................................................ 59
2.1 WhatisPlasma? ................................................ 59
2.1.1 Debyeshielding .......................................... 60
2.1.2 Plasmaoscillations........................................ 61
2.1.3 Gyromotion ............................................. 62
2.1.4 Collisions ............................................... 63
2.2 BasicElectrodynamics ........................................... 64
2.2.1 Maxwell’sequations ...................................... 64
2.2.2 Lorentzforce............................................. 66
2.2.3 Potentials................................................ 66
2.2.4 Energyconservation....................................... 70
2.2.5 Chargedparticlesinelectromagneticfields.................... 71
2.3 ToolsofStatisticalPhysics........................................ 73
2.3.1 Plasmainthermalequilibrium .............................. 73
2.3.2 DerivationofVlasovandBoltzmannequations ................ 75
2.3.3 Macroscopicvariables ..................................... 78
2.3.4 Derivationofmacroscopicequations ......................... 80
2.3.5 Equationsofmagnetohydrodynamics ........................ 82
2.3.6 Doubleadiabatictheory.................................... 86
3. SingleParticleMotion ............................................... 89
3.1 MagneticDrifts ................................................. 89
3.2 AdiabaticInvariants ............................................. 93
3.2.1 Thefirstadiabaticinvariant................................. 93
3.2.2 Magneticmirrorandmagneticbottle......................... 95
3.2.3 Thesecondadiabaticinvariant .............................. 96
3.2.4 BetatronandFermiacceleration............................. 96
3.2.5 Thethirdadiabaticinvariant ................................ 97
3.3 MotionintheDipoleField........................................ 98
3.4 MotionNearaCurrentSheet ...................................... 103
3.4.1 TheHarrismodel ......................................... 104
3.4.2 Neutralsheetwithaconstantelectricfield .................... 106
3.4.3 Currentsheetwithasmallperpendicularmagneticfieldcomponent107
3.5 MotioninaTime-dependentElectricField .......................... 108
3.5.1 Slowtimevariations....................................... 108
3.5.2 Timevariationsinresonancewithgyromotion ................ 108
3.5.3 High-frequencyfields...................................... 109
4. WavesinColdPlasmaApproximation................................. 113
4.1 BasicConcepts ................................................. 113
4.1.1 Wavesinlinearmedia ..................................... 113
4.1.2 Wavepolarization......................................... 117
4.1.3 Reflectionandrefraction ................................... 118
4.2 RadioWavePropagationintheIonosphere .......................... 121
4.2.1 Isotropic,losslessionosphere ............................... 121
Contents VII
4.2.2 Weaklyinhomogeneousionosphere.......................... 124
4.2.3 Inclusionofcollisions ..................................... 128
4.2.4 Inclusionofthemagneticfield .............................. 129
4.3 GeneralTreatmentofColdPlasmaWaves ........................... 130
4.3.1 Dispersionequationforcoldplasmawaves.................... 130
4.3.2 Parallelpropagation(θ =0)................................ 133
4.3.3 Perpendicularpropagation(θ =π/2) ........................ 136
4.3.4 Propagationatarbitraryangles .............................. 137
5. VlasovTheory ...................................................... 141
5.1 PropertiesoftheVlasovEquation.................................. 141
5.2 Landau’sSolution ............................................... 143
5.3 NormalModesinaMaxwellianPlasma............................. 148
5.3.1 Theplasmadispersionfunction ............................. 148
5.3.2 TheLangmuirwave ....................................... 149
5.3.3 Theion–acousticwave..................................... 150
5.3.4 MacroscopicderivationofLangmuirandion–acousticmodes .... 151
5.4 PhysicsofLandauDamping ...................................... 153
5.5 VlasovTheoryinaGeneralEquilibrium ............................ 155
5.6 UniformlyMagnetizedPlasma .................................... 157
5.6.1 Perpendicularpropagation(θ =π/2) ........................ 159
5.6.2 Parallelpropagation(θ =0) ................................ 161
5.6.3 Propagationatarbitraryangles .............................. 161
6. Magnetohydrodynamics ............................................. 163
6.1 FromHydrodynamicstoConservativeMHDEquations................ 163
6.2 ConvectionandDiffusion......................................... 166
6.3 Frozen-inFieldLines ............................................ 168
6.4 MagnetohydrostaticEquilibrium................................... 171
6.5 Field-alignedCurrents ........................................... 173
6.5.1 Force-freefields .......................................... 173
6.5.2 Grad–Shafranovequation .................................. 176
6.5.3 Generalpropertiesofforce-freefields ........................ 177
6.5.4 FACsandthemagnetosphere–ionospherecoupling ............. 178
6.5.5 Magnetichelicity ......................................... 180
6.6 Alfve´nWaves................................................... 183
6.6.1 DispersionequationofMHDwaves.......................... 183
6.6.2 MHDwavemodes ........................................ 184
6.7 BeyondMHD .................................................. 186
6.7.1 Quasi-neutralhybridapproach .............................. 187
6.7.2 KineticAlfve´nwaves...................................... 189
VIII Contents
7. SpacePlasmaInstabilities............................................ 191
7.1 Beam–plasmaModes ............................................ 192
7.1.1 Two-streaminstability ..................................... 193
7.1.2 Bunemaninstability ....................................... 195
7.2 Macroinstabilities ............................................... 196
7.2.1 Rayleigh–Taylorinstability................................. 196
7.2.2 Farley–Bunemaninstability................................. 199
7.2.3 Ballooninginstability...................................... 200
7.2.4 Kelvin–Helmholtzinstability ............................... 202
7.2.5 Firehoseandmirrorinstabilities ............................. 204
7.2.6 Fluxtubeinstabilities...................................... 206
7.3 Microinstabilities................................................ 207
7.3.1 Monotonicallydecreasingdistributionfunction ................ 207
7.3.2 Multiple-peakeddistributions ............................... 208
7.3.3 Ion–acousticinstability .................................... 210
7.3.4 Electrostaticioncyclotroninstability......................... 212
7.3.5 Current-driveninstabilitiesperpendiculartoB ................. 213
7.3.6 Electromagneticcyclotroninstabilities ....................... 215
7.3.7 Ionbeaminstabilities...................................... 217
8. MagneticReconnection .............................................. 219
8.1 BasicsofReconnection........................................... 219
8.1.1 ClassicalMHDdescriptionofreconnection ................... 220
8.1.2 TheSweet–Parkermodel................................... 221
8.1.3 ThePetschekmodel....................................... 223
8.1.4 Asymmetricreconnection .................................. 225
8.2 CollisionlessReconnection ....................................... 227
8.2.1 Thetearingmode ......................................... 228
8.2.2 Thecollisionlesstearingmode .............................. 229
8.2.3 Tearingmodeorsomethingelse? ............................ 231
8.2.4 TheHalleffect ........................................... 232
8.3 ReconnectionandDynamo ....................................... 236
8.3.1 Currentgenerationatthemagnetosphericboundary ............ 236
8.3.2 Elementsofsolardynamotheory ............................ 238
8.3.3 Thekinematicαω dynamo................................. 241
9. PlasmaRadiationandScattering ..................................... 245
9.1 SimpleAntennas ................................................ 245
9.2 RadiationofaMovingCharge..................................... 248
9.3 Bremsstrahlung ................................................. 251
9.4 CyclotronandSynchrotronRadiation............................... 255
9.5 ScatteringfromPlasmaFluctuations................................ 258
9.6 ThomsonScattering ............................................. 261
Contents IX
10. TransportandDiffusioninSpacePlasmas ............................. 267
10.1 ParticleFluxandPhaseSpaceDensity.............................. 267
10.2 CoordinatesforParticleFluxDescription ........................... 269
10.3 ElementsofFokker–PlanckTheory ................................ 271
10.4 Quasi-LinearDiffusionThroughWave–ParticleInteraction ............ 273
10.5 KineticEquationwithFokker–PlanckTerms......................... 276
11. ShocksandShockAcceleration ....................................... 279
11.1 BasicShockFormation........................................... 280
11.1.1 Steepeningofcontinuousstructures.......................... 280
11.1.2 Hydrodynamicshocks ..................................... 282
11.2 ShocksinMHD................................................. 283
11.2.1 Perpendicularshocks ...................................... 283
11.2.2 Obliqueshocks ........................................... 285
11.2.3 Rotationalandtangentialdiscontinuities...................... 287
11.2.4 Thicknessoftheshockfront ................................ 288
11.2.5 Collisionlessshockwavestructure........................... 290
11.3 ParticleAccelerationinShockWaves............................... 293
11.3.1 Shockdriftacceleration.................................... 294
11.3.2 Diffusiveshockacceleration ................................ 295
11.3.3 Shocksurfingacceleration.................................. 297
12. StormsontheSun................................................... 299
12.1 ProminencesandCoronalLoops................................... 300
12.2 RadioStormsontheSun ......................................... 302
12.2.1 Classificationofradioemissions ............................ 303
12.2.2 Physicalmechanismsforsolarradioemissions ................ 304
12.3 SolarFlares .................................................... 307
12.3.1 Observationalcharacteristicsofsolarflares.................... 307
12.3.2 Physicsofsolarflares...................................... 311
12.4 CoronalMassEjections .......................................... 314
12.4.1 CMEsneartheSun........................................ 315
12.4.2 Propagationtimeto1AU .................................. 317
12.4.3 MagneticstructureofICMEs ............................... 318
12.5 CMEs,FlaresandParticleAcceleration ............................. 320
13. MagnetosphericStormsandSubstorms................................ 323
13.1 WhatareMagneticStormsandSubstorms?.......................... 323
13.1.1 Stormbasics ............................................. 324
13.1.2 Theconceptofsubstorm ................................... 326
13.1.3 Observationalsignaturesofsubstorms........................ 326
13.2 PhysicsofSubstormOnset........................................ 333
13.2.1 Theoutside–inview....................................... 334
13.2.2 Theinside–outview....................................... 339
13.2.3 Externaltriggeringofsubstormexpansion .................... 342