Preface page ................................................. xiii
1. The wind from the Sun: an introduction ...................... 1
1.1. A brief history of ideas .............................. 1
1.1.1. Intermittent particle beams? .................. 2
1.1.2. Permanent solar corpuscular emission? ......... 4
1.1.3. The modern solar wind ......................... 6
1.2. Looking at the Sun .................................... 8
1.2.1. Basic solar properties ........................ 9
1.2.2. The solar spectrum ........................... 10
1.2.3. The solar disc ............................... 13
1.2.4. Sunspots, magnetic fields and the solar
cycle ........................................ 15
1.2.5. Around the Sun: chromosphere and corona ...... 18
1.3. Observing the solar wind ............................. 24
1.3.1. Observing near the ecliptic .................. 24
1.3.2. Exploring the third dimension with Ulysses ... 28
1.3.3. A simplified three-dimensional picture ....... 33
References ................................................. 37
2. Tool kit for space plasma physics .......................... 41
2.1. What is a plasma? .................................... 42
2.1.1. Gaseous plasma ............................... 44
2.1.2. Quasi-neutrality ............................. 44
2.1.3. Collisions of charged particles .............. 48
2.1.4. Plasma oscillations .......................... 54
2.1.5. Non-classical plasmas ........................ 56
2.1.6. Summary ...................................... 57
2.2. Dynamics of a charged particle ....................... 58
2.2.1. The key role of the magnetic field ........... 58
2.2.2. Basic charge motion in constant and uniform
fields ....................................... 59
2.2.3. Non-uniform magnetic field ................... 62
2.2.4. Adiabatic invariants ......................... 65
2.2.5. Summary ...................................... 66
2.3. Many particles: from kinetics to
magnetohydrodynamics ................................. 66
2.3.1. Elements of plasma kinetics .................. 66
2.3.2. First-aid kit for space plasma fluids ........ 72
2.3.3. Elements of magnetohydrodynamics ............. 85
2.3.4. Waves and instabilities ...................... 96
2.3.5. Summary ..................................... 100
2.4. Basic tools for ionisation .......................... 101
2.4.1. Energy of ionisation and the size of the
hydrogen atom ............................... 101
2.4.2. Ionisation by compressing or heating ........ 102
2.4.3. Radiative ionisation and recombination ...... 103
2.4.4. Non-radiative ionisation and
recombination ............................... 105
2.5. Problems ............................................ 107
2.5.1. Linear Debye shielding in a
non-equilibrium plasma ...................... 107
2.5.2. Mean free path in a plasma .................. 108
2.5.3. Particles trapped in a planetary
magnetic field .............................. 108
2.5.4. Filtration of particles in the absence of
equilibrium ................................. 109
2.5.5. Freezing of magnetic field lines ............ 110
2.5.6. Alfven wave ................................. 110
2.5.7. Why is the solar wind ionised? .............. 110
References ................................................ 110
3. Anatomy of the Sun ........................................ 113
3.1. An (almost) ordinary star ........................... 113
3.1.1. Hydrostatic equilibrium of a large ball
of plasma ................................... 114
3.1.2. Luminosity .................................. 116
3.1.3. Energy source and timescales ................ 118
3.1.4. The mass of a normal star ................... 121
3.2. Structure and dynamics .............................. 123
3.2.1. Modelling the solar interior ................ 124
3.2.2. Convective instability ...................... 125
3.2.3. Convective energy transfer .................. 128
3.2.4. The quiet photosphere ....................... 132
3.2.5. Solar rotation .............................. 135
3.3. Some guesses on solar magnetism ..................... 137
3.3.1. Elements of dynamo theory ................... 138
3.3.2. Solar kinematic dynamos ..................... 142
3.3.3. Concentrating and expelling the magnetic
field ....................................... 145
3.3.4. Lorentz force restriction on dynamo
action ...................................... 148
3.3.5. Elementary physics of magnetic flux tubes ... 149
3.3.6. Surface magnetic field ...................... 154
3.4. Problems ............................................ 158
3.4.1. Conductive heat transfer in the solar
interior .................................... 158
3.4.2. Timescale for radiative transport ........... 158
3.4.3. Solar differential rotation ................. 158
3.4.4. Twisted magnetic flux tube .................. 159
3.4.5. The heat flux blocked by sunspots ........... 159
References ................................................ 160
4. The outer solar atmosphere ................................ 165
4.1. From the photosphere to the corona .................. 166
4.1.1. The atmosphere in one dimension ............. 166
4.1.2. One more dimension .......................... 168
4.1.3. Three dimensions in space ................... 169
4.1.4. ... and one dimension in time ............... 169
4.1.5. A (tentative) look at the solar jungle ...... 172
4.2. Force balance and magnetic structures ............... 174
4.2.1. Forces ...................................... 175
4.2.2. Force-free magnetic field ................... 177
4.2.3. Magnetic helicity ........................... 181
4.2.4. Inferences on magnetic structure in
the low corona .............................. 185
4.3. Energy balance ...................................... 186
4.3.1. Radiative losses ............................ 186
4.3.2. Radiative and conductive timescales ......... 187
4.3.3. Temperature structure ....................... 188
4.4. Some prominent species .............................. 190
4.4.1. Spicules .................................... 190
4.4.2. Magnetic loops .............................. 191
4.4.3. Prominences ................................. 193
4.5. Time variability .................................... 194
4.5.1. Empirical facts ............................. 194
4.5.2. Hints from physics .......................... 197
4.5.3. Further difficult questions ................. 200
4.6. Coronal heating: boojums at work? ................... 203
4.6.1. The energy budget and how to balance it ..... 204
4.6.2. Heating through reconnection events ......... 205
4.6.3. Heating by waves ............................ 206
4.6.4. Filtration of a non-Maxwellian velocity
distribution ................................ 209
4.7. Hydrostatic instability of the corona ............... 214
4.7.1. Simplified picture of a static
atmosphere .................................. 214
4.7.2. Magnetic field effects ...................... 215
4.8. Problems ............................................ 217
4.8.1. Elementary temperature profile ............... 217
4.8.2. Helicity of a string wrapped around
a doughnut ................................... 217
4.8.3. A static solar atmosphere? .................. 218
References ................................................ 218
5. How does the solar wind blow? ............................. 223
5.1. The basic problem ................................... 225
5.1.1. The solar wind on the back of an envelope ... 225
5.1.2. Nasty questions, or why it is complicated ... 227
5.2. Simple fluid theory ................................. 228
5.2.1. The isothermal approximation ................ 228
5.2.2. Breeze, wind or accretion? .................. 232
5.3. Letting the temperature vary ........................ 237
5.3.1. Energy balance .............................. 237
5.3.2. Poly trope approximation .................... 239
5.3.3. Changing the geometry ....................... 246
5.3.4. Further pushing or heating the wind ......... 247
5.3.5. What about viscosity? ....................... 249
5.4. A mixture of fluids ................................. 250
5.4.1. Simple balance equations .................... 251
5.4.2. Observed proton and electron temperatures ... 253
5.4.3. The role of collisions ...................... 254
5.4.4. Heat flux ................................... 256
5.4.5. The electric field .......................... 257
5.4.6. Fluid picture balance sheet and
refinements ................................. 261
5.5. Kinetic descriptions ................................ 262
5.5.1. Some notations .............................. 262
5.5.2. Observed proton and electron velocity
distributions ............................... 263
5.5.3. Non-collisional electron heat flux .......... 267
5.5.4. Exospheric models ........................... 268
5.5.5. Kinetic models with collisions and
wave particle interactions .................. 273
5.6. Building a 'full' theory? ........................... 274
5.6.1. More and better observations (beware of
hidden assumptions) ......................... 274
5.6.2. Difficult theoretical questions ............. 275
5.7. Problems ............................................ 277
5.7.1. Transonic flows in ducts: the de Laval
nozzle ...................................... 277
5.7.2. The hysteresis cycle of an isothermal
flow ........................................ 279
5.7.3. Spherical accretion by a star: the Bondi
problem ..................................... 280
5.7.4. A wind with polytrope protons and
electrons ................................... 281
5.7.5. Playing with the kappa distribution ......... 282
5.7.6. 'Temperature' or 'temperatures'? ............ 283
5.7.7. Non-collisional heat flux ................... 284
5.7.8. An imaginary wind with charges of equal
masses ...................................... 285
References ................................................ 286
6. Structure and perturbations ............................... 291
6.1. Basic large-scale magnetic field .................... 291
6.1.1. Parker's spiral ............................. 291
6.1.2. Basic heliospheric current sheet and other
currents .................................... 296
6.1.3. Magnetic field effects on the wind .......... 299
6.2. Three-dimensional structure during the solar
cycle ............................................... 300
6.2.1. Warped heliospheric current sheet ........... 301
6.2.2. Observed large-scale structure .............. 301
6.2.3. Connecting the Sun and the solar wind, or:
where do the fast and slow winds come
from? ....................................... 305
6.3. Major perturbations ................................. 308
6.3.1. Interaction between the fast and slow
winds ....................................... 308
6.3.2. Coronal mass ejections in the solar wind .... 309
6.3.3. Associated shocks ........................... 311
6.4. Waves and turbulence ................................ 315
6.4.1. Waves ....................................... 315
6.4.2. Turbulence .................................. 318
6.5. Minor constituents .................................. 326
6.5.1. Abundances: from the Universe to the
solar wind .................................. 326
6.5.2. Helium and heavier solar wind ions .......... 327
6.5.3. Pick-up ions ................................ 328
6.6. Problems ............................................ 329
6.6.1. Parker's spiral ............................. 329
6.6.2. Heliospheric currents ....................... 329
6.6.3. Coplanarity in MHD shocks ................... 330
6.6.4. Kraichnan's spectrum in magnetofluid
turbulence .................................. 330
References ................................................ 330
7. Bodies in the wind: dust, asteroids, planets and comets ... 335
7.1. Bodies in the wind .................................. 336
7.1.1. Various bodies .............................. 336
7.1.2. Mass distribution ........................... 338
7.1.3. Mass versus size ............................ 341
7.1.4. Atmospheres and how they are ionised ........ 344
7.1.5. Planetary magnetic fields and ionospheric
conductivity ................................ 347
7.2. Basics of the interaction ........................... 348
7.2.1. Properties and spatial scales of the
flow ........................................ 348
7.2.2. Being small: electrostatic charging and
wakes ....................................... 352
7.2.3. Being large: the importance of
conductivity ................................ 358
7.2.4. Large objects with a conducting
atmosphere .................................. 362
7.2.5. Large magnetised objects .................... 365
7.2.6. Bow shocks .................................. 368
7.2.7. Not being constant: sputtering and
evaporation ................................. 371
7.3. The magnetospheric engine ........................... 372
7.3.1. Basic structure ............................. 375
7.3.2. Energy, coupling and timescales ............. 378
7.3.3. Storms, substorms and auroras ............... 385
7.4. Physics of heliospheric dust grains ................. 390
7.4.1. Forces ...................................... 390
7.4.2. Evaporation ................................. 394
7.5. Comets .............................................. 394
7.5.1. Producing an atmosphere ..................... 397
7.5.2. Ionising the atmosphere ..................... 400
7.5.3. Pick-up of cometary ions .................... 401
7.5.4. Magnetic pile-up ............................ 403
7.5.5. The plasma tail ............................. 404
7.5.6. X-ray emission .............................. 406
7.5.7. The dust tail ............................... 408
7.6. Problems ............................................ 409
7.6.1. Electrostatic charging in space ............. 409
7.6.2. Magnetic pile-up ............................ 409
7.6.3. Chapman-Ferraro layer ....................... 410
7.6.4. Interaction of the solar wind with Venus
and Mars .................................... 411
7.6.5. Ring current ................................ 411
7.6.6. Does Vesta have a magnetosphere? ............ 412
7.6.7. Gas-dust drag in a comet: another nozzle
problem ..................................... 412
References ................................................ 413
8. The solar wind in the Universe ............................ 419
8.1. The frontier of the heliosphere ..................... 419
8.1.1. The Local Cloud ............................. 420
8.1.2. Basics of the interaction ................... 421
8.1.3. The size of the solar wind bubble ........... 424
8.2. Cosmic rays ......................................... 425
8.2.1. Cosmic rays observed near Earth ............. 426
8.2.2. Rudiments of the acceleration of
particles ................................... 430
8.2.3. Modulation of galactic cosmic rays by
solar activity .............................. 436
8.2.4. 'Anomalous cosmic rays' ..................... 439
8.3. Examples of winds in the Universe ................... 440
8.3.1. Some basic physical processes in mass
outflows .................................... 441
8.3.2. Some empirical results on stellar winds ..... 443
8.3.3. The efficiency of the wind engine ........... 445
8.4. Problems ............................................ 448
8.4.1. Energy density of cosmic rays ............... 448
8.4.2. Power law distribution of accelerated
particles ................................... 448
8.4.3. The size of an astrosphere .................. 448
8.4.4. Instability of a star's atmosphere
produced by radiation pressure .............. 448
References ................................................ 449
Appendix ...................................................... 451
Index ......................................................... 457
|
