The Heliosphere through the Solar Activity Cycle (eBook)

Contents 5
Preface 10
Acknowledgments 13
Figures 14
Abbreviations and acronyms 19
The heliosphere: Its origin and exploration 22
1.1 INTRODUCTION 22
1.2 THE PRE–SPACE AGE HELIOSPHERE 23
1.2.1 The expanding hot solar atmosphere 23
1.2.2 Energetic particles in the heliosphere 26
1.3 THE HELIOSPHERE AND ITS BOUNDARIES 28
1.3.1 The size of the heliosphere 29
1.3.2 The termination shock and beyond: Voyager 1 results 32
1.4 HELIOSPHERIC STRUCTURE AND DYNAMICS OVER THE SOLAR CYCLE 33
1.4.1 The solar wind through the solar activity cycle 33
1.4.2 Close to solar-minimum activity: corotating interaction regions 35
1.4.3 Around solar-maximum activity: coronal mass ejections 35
1.4.4 Energetic solar particles 36
1.4.5 Large-scale structures and the modulation of cosmic rays 37
1.5 THE EXPLORATION OF THE HELIOSPHERE 37
1.5.1 Inner heliosphere 37
1.5.2 Earth-orbiting missions 38
1.5.3 L1 spacecraft 38
1.5.4 Outer heliosphere 39
1.5.5 Future heliosphere missions 39
1.5.6 Summary 40
1.6 REFERENCES 40
Solar cycle 23 42
2.1 INTRODUCTION 42
2.2 SOLAR ACTIVITY CYCLES 43
2.3 CYCLE 23 48
2.4 THE EXTENSION OF CYCLE 23 INTO THE INTERPLANETARY MEDIUM 52
2.5 SUMMARY 58
2.6 ACKNOWLEDGMENTS 58
2.7 REFERENCES 59
The solar wind throughout the solar cycle 61
3.1 INTRODUCTION: THE PRE-ULYSSES PICTURE 61
3.2 MORPHOLOGY 64
3.3 DISTRIBUTION FUNCTIONS 69
3.3.1 H and He distribution functions 69
3.3.2 Heavy ion distribution functions 71
3.4 COMPOSITION 73
3.4.1 Charge-state composition 74
3.4.2 Elemental composition 78
3.4.3 Correlation between composition and kinetic parameters 81
3.5 TRANSIENTS 82
3.5.1 Corotating interaction regions 82
3.5.2 Coronal mass ejections 84
3.5.3 Other transients 88
3.6 THE ULYSSES PICTURE: THE SOLAR WIND IN FOUR DIMENSIONS 90
3.7 ACKNOWLEDGMENTS 91
3.8 REFERENCES 91
The global heliospheric magnetic field 99
4.1 INTRODUCTION 99
4.2 THE HELIOSPHERIC MAGNETIC FIELD: A GLOBAL PERSPECTIVE 100
4.2.1 The Parker field model 100
4.2.2 BR and open flux 104
4.2.3 BT and the Parker spiral angle 107
4.2.4 The north–south component, BN 113
4.3 THE HELIOSPHERIC MAGNETIC FIELD AT SOLAR MINIMUM 115
4.3.1 Dipole tilt, sector structure, and heliospheric current sheet 115
4.3.2 Sector structure and source surface models 117
4.3.3 Heliospheric current sheet and plasma sheet: properties 118
4.3.4 The HMF and testing of source surface models 121
4.4 THE HMF AND HELIOSPHERIC STRUCTURE 123
4.4.1 Solar and solar wind structure 123
4.4.2 Evolution and interaction of fast and slow wind 125
4.4.3 CIRs, shocks, and dipole tilt 128
4.4.4 CIRs, energetic particles, and their access to high latitudes 131
4.4.5 Corotating rarefaction regions and the spiral angle 136
4.4.6 Magnetic .eld strength and flux deficit 138
4.5 NORTH–SOUTH ASYMMETRY OF THE SOLAR DIPOLE AND ITS SOLAR CYCLE VARIATION 140
4.6 TEMPORAL VARIATIONS—CORONAL MASS EJECTIONS 143
4.7 HMF AT SOLAR MAXIMUM AND ITS SOLAR CYCLE VARIATION 145
4.7.1 Introduction to solar maximum and the Hale cycle 145
4.7.2 Solar magnetic field at solar maximum 145
4.7.3 Magnetic dipole and polarity reversal 148
4.7.4 Inclination of the HCS and solar dipole 149
4.7.5 The radial component at solar maximum 154
4.7.6 Solar cycle variation of open flux 156
4.7.7 Solar cycle variations in field magnitude 158
4.8 SUMMARY—SOLAR CYCLE VARIATIONS 159
4.9 ACKNOWLEDGMENTS 164
4.10 REFERENCES 164
Heliospheric energetic particle variations 171
5.1 ENERGETIC PARTICLE POPULATIONS IN THE INNER HELIOSPHERE 171
5.2 SOLAR MINIMUM ORBIT (1992–1998) 172
5.2.1 Summary of the Ulysses solar-minimum observations 174
5.2.2 Energetic particle origin, transport, and acceleration processes in the solar minimum inner heliosphere - 176
5.3 SOLAR MAXIMUM ORBIT (1998–2004) 179
5.5 MULTI-SPACECRAFT OBSERVATIONS OF SEP EVENTS: ULYSSES AND NEAR- EARTH OBSERVATIONS 188
5.6 HELIOSPHERIC ENERGETIC PARTICLE RESERVOIRS 199
5.7 INFLUENCE OF INTERPLANETARY STRUCTURES ON SEP PROPAGATION 203
5.9 ACKNOWLEDGMENTS 207
5.10 REFERENCES 208
Galactic and anomalous cosmic rays through the solar cycle: New insights from Ulysses 215
6.1 INTRODUCTION 215
6.1.1 Particle populations in the heliosphere 215
6.1.2 Cosmic ray modulation 216
6.2 SELECTED COSMIC RAY OBSERVATIONS 219
6.2.1 Observations close to Earth 220
6.2.2 The transport equation 223
6.2.3 The diffusion tensor 227
6.2.4 Solar wind, magnetic field, and the current sheet 228
6.2.5 Size and geometry of the heliosphere 230
6.2.6 Termination shock and anomalous cosmic rays 231
6.2.7 Local interstellar spectra 232
6.2.8 Cosmic ray modulation models 233
6.2.9 Modeling the 11-year and 22-year cycles 234
6.2.10 The compound modeling approach to long-term modulation 235
6.3 COSMIC RAY DISTRIBUTION AT SOLAR MINIMA 236
6.3.1 Ulysses observations at solar minimum 238
6.4 THE TRANSITION FROM SOLAR MINIMUM TO SOLAR MAXIMUM 244
6.4.1 Galactic cosmic rays during the 1990–2000 A> 0 solar magnetic cycle
6.4.2 MeV electrons 252
6.5 SUMMARY 255
6.5.1 Solar minimum 255
6.5.2 Solar maximum 257
6.5.3 Insights on particle propagation in a turbulent astrophysical plasma 258
6.5.4 Cosmic ray modulation surprises from Ulysses 258
6.6 ACKNOWLEDGMENTS 259
6.7 REFERENCES 259
Overview: The heliosphere then and now 270
7.1 INTRODUCTION 270
7.2 THE KNOWN HELIOSPHERE IN 1992 272
7.2.1 The solar wind and the heliospheric magnetic field 273
7.2.2 Solar wind composition and ionization state 276
7.2.3 Energetic particles and cosmic rays 277
7.2.4 Interstellar and interplanetary neutral gas 279
7.2.5 Interstellar and interplanetary dust 279
7.3 THE KNOWN HELIOSPHERE AFTER A SOLAR ACTIVITY CYCLE WITH ULYSSES 280
7.3.1 The global view 280
7.3.2 Coronal and heliospheric magnetic fields 283
7.3.3 Composition and ionization state 286
7.3.4 Coronal mass ejections 287
7.3.5 Energetic particles 287
7.3.6 Cosmic rays 291
7.3.7 The heliosphere–interstellar medium interface 293
7.3.8 Summary 294
7.4 ACKNOWLEDGMENTS 296
7.5 REFERENCES 296
Index 299