Reconnection of Magnetic Fields: Magnetohydrodynamics and Collisionless Theory and Observations

Cover......Page 1
Half-title......Page 3
Title......Page 5
Copyright......Page 6
Contents......Page 7
Contributors......Page 9
Preface......Page 13
Acknowledgments......Page 14
1 Introduction......Page 15
1.1 The Sun......Page 17
1.1.1 Solar flares......Page 18
1.2 Earth’s magnetosphere......Page 22
2.1 Classical theory of two-dimensional reconnection......Page 30
2.1.1 Steady-state reconnection......Page 31
2.1.2 Time-dependent reconnection......Page 38
2.2 Fundamental concepts......Page 39
2.2.1 Topological conservation laws......Page 40
Relations between conservation laws......Page 43
Preparation for reconnection: detachment of a drop......Page 44
2.2.2 Conditions for magnetic reconnection to occur......Page 47
Solutions for nonvanishing B......Page 49
Solutions at null points of B......Page 50
Solutions for E·B = 0......Page 51
2.2.3 Two-dimensional reconnection......Page 52
2.2.4 Three-dimensional reconnection: E B= 0......Page 55
2.2.5 Three-dimensional reconnection: E B = 0......Page 56
2.3 Three-dimensional reconnection in the absence of magnetic null points......Page 59
2.3.1 The model......Page 61
2.3.2 Purely rotational solutions......Page 65
2.3.3 Reconnected flux......Page 66
2.3.4 Composite solutions......Page 69
Evolution of the magnetic flux......Page 70
Reconnection rate......Page 74
2.3.5 The two-dimensional limit......Page 75
2.4 Three-dimensional reconnection at magnetic null points......Page 76
2.4.1 Properties of 3D reconnection......Page 78
The model......Page 79
The solution......Page 82
2.4.3 Fan-aligned current......Page 85
2.4.4 Summary......Page 86
2.5.1 Untwisted flux tube reconnection......Page 88
2.5.2 Twisted flux tube reconnection......Page 93
2.5.3 Helicity conservation and energy release: tunnel vs. slingshot......Page 96
2.5.4 Summary......Page 99
3.1 Fundamentals of collisionless reconnection......Page 101
3.1.1 Basic kinetic processes and scales......Page 103
Reconnection with antiparallel magnetic fields......Page 105
Reconnection with a guide field......Page 110
3.1.2 Scaling of kinetic reconnection to macroscale systems......Page 116
3.1.3 Transitions from slow to fast reconnection......Page 119
3.2 Diffusion region physics......Page 122
3.2.2 Antiparallel reconnection......Page 123
3.2.3 Guide field reconnection......Page 128
3.3 Onset of magnetic reconnection......Page 135
3.3.1 The pure ion tearing instability......Page 136
3.3.2 Electron stabilization of ion tearing......Page 137
Effects of turbulence......Page 138
Fluid treatment......Page 139
Transient electrons......Page 140
3.3.3 Effects of the third dimension......Page 141
3.3.4 Externally driven reconnection......Page 142
3.3.5 Summary and outlook......Page 145
3.4 Hall MHD reconnection......Page 146
3.4.1 Impulsive Hall MHD reconnection......Page 147
3.4.2 Resistive Hall MHD reconnection scaling: Role of flux pile-up......Page 154
3.5 Role of current-aligned instabilities......Page 158
3.5.1 Ion-acoustic instability......Page 159
3.5.2 Lower-hybrid drift instability......Page 160
3.5.3 Lower-hybrid drift instability in non-antiparallel fields......Page 163
3.5.4 Kink instability......Page 164
3.5.6 Modified two-stream instability......Page 166
3.5.7 Summary and conclusions......Page 167
3.6.1 Basic plasma parameters in the magnetosphere......Page 168
3.6.2 Energetic particle observations and magnetic reconnection......Page 170
3.6.3 Acceleration of test particles under MHD reconnection fields......Page 172
3.6.4 Turbulence and wave scattering......Page 173
3.6.5 Strong acceleration during reconnection......Page 174
3.6.6 Discussions and remaining problems......Page 179
4 Reconnection in the magnetosphere......Page 181
4.1 Reconnection at the magnetopause: concepts and models......Page 182
4.1.1 Three-dimensional reconnection at the dayside magnetopause......Page 184
4.1.2 The Sweet–Parker time scale problem......Page 186
4.1.3 Global MHD simulations of magnetopause reconnection......Page 188
4.1.4 Summary......Page 193
4.2 Observations of magnetopause reconnection......Page 194
4.2.1 When does magnetopause reconnection occur?......Page 195
4.2.2 Where does magnetopause reconnection occur?......Page 196
4.2.3 The stability of high-latitude reconnection......Page 200
4.2.4 The variability of reconnection......Page 201
4.2.5 Conclusions and discussion......Page 205
4.3 Stability of the magnetotail......Page 206
4.3.1 MHD stability of magnetotail-like configurations......Page 207
Stability criterion......Page 208
Results and interpretation......Page 209
4.3.2 Collisionless tearing......Page 212
4.3.3 Discussion......Page 214
4.4.1 Thin current sheet formation......Page 215
4.4.2 Plasmoid formation and structure......Page 217
4.4.3 Plasma flow and the substorm current wedge......Page 219
4.4.4 Particle acceleration......Page 220
4.5.1 Cluster tetrahedron......Page 223
4.5.2 Current sheet structure......Page 224
4.5.3 X-line encounter and Hall currents......Page 225
4.5.5 Hall current closure......Page 228
4.5.6 Other features......Page 229
4.5.7 Consequences of tail reconnection......Page 230
4.6 Remote sensing of reconnection......Page 231
4.6.1 Method......Page 232
Position and velocity of the reconnection separatrix......Page 234
Pioneering studies......Page 237
State of the art studies......Page 238
4.6.3 Discussion......Page 240
5.1 Coronal heating......Page 243
5.1.1 X-ray bright points: driven reconnection......Page 245
5.1.3 Binary reconnection......Page 246
5.1.4 Separator reconnection......Page 247
5.1.5 Coronal tectonics......Page 249
5.1.7 Conclusion......Page 250
5.2.1 X-point current in two dimensions......Page 251
5.2.2 Separator current in three dimensions......Page 256
5.2.3 Initiation of reconnection......Page 259
5.2.4 Observation of separator reconnection......Page 260
5.2.5 Summary......Page 263
5.3.1 Definition of QSL......Page 264
5.3.2 Examples of QSLs......Page 266
5.3.3 Implications for the process of current layer formation......Page 269
5.4.1 The photospheric–coronal connection......Page 272
5.4.2 Magnetic nulls and separators......Page 273
5.4.3 Flybys......Page 276
5.4.4 Flux braiding......Page 283
5.4.5 Summary......Page 288
5.5 Solar flares......Page 289
5.5.1 Ideal MHD processes......Page 290
5.5.2 Morphological models......Page 292
5.5.4 Reversed-shear flare model......Page 293
5.6 Particle acceleration in flares: theory......Page 295
5.6.1 Direct acceleration by the reconnection electric field......Page 296
5.6.2 Acceleration mechanisms associated with reconnection......Page 301
5.6.3 Other acceleration mechanisms......Page 303
5.7 Fast particles in flares: observations......Page 305
5.7.1 Hard X-ray emission......Page 306
5.7.2 HXR spectroscopy......Page 307
5.7.3 Flare imaging: HXR to infrared......Page 309
Footpoint motions......Page 310
Coronal HXR sources......Page 311
5.7.4 Nonthermal radio emissions......Page 312
5.7.5 Ions......Page 313
5.7.6 Conclusions......Page 314
Definition of specific notations......Page 316
References......Page 317
Index......Page 353