Conversations on Electric and Magnetic Fields in the Cosmos

List of Illustrations xi
Acknowledgments xiii

Chapter 1: Introduction 1

1.1 General Remarks 1

1.2 Electromagnetic Field Equations 3

1.3 Electrical Neutrality 7

1.4 Electric Charge and Magnetic Field Dominance 12

Chapter 2: Electric Fields 15

2.1 Basic Considerations 15

2.2 Definition of Charge and Field 16

2.3 Concept of Electric Field 17

2.4 Physical Reality of Electric Field 20

2.5 Electric Field Pressure 22

Chapter 3: Magnetic Fields 25

3.1 Basic Considerations 25

3.2 Experimental Connection 26

3.3 Differential Form of Ampere's Law 27

3.4 Energy and Stress 29

3.5 Detecting a Magnetic Field 32

Chapter 4: Field Lines 37

4.1 Basic Considerations 37

4.2 The Optical Analogy 39

Chapter 5: Maxwell's Equations 43

Chapter 6: Maxwell and Poynting 48

6.1 Poynting's Momentum and Energy Theorems 48

6.2 Applications 52

6.3 Electric and Magnetic Fields in Matter 52

6.4 SI Units 55

6.5 Systems of Units 59

6.6 Chaucer Units 63

Chapter 7: Moving Reference Frames 65

7.1 Lorentz Transformations 65

7.2 Electric Fields in the Laboratory 66

7.3 Occam's Razor and the Tree in the Forest 67

7.4 Electric Field in a Moving Plasma 68

7.5 Net Charge in a Swirling Plasma 71

Chapter 8: Hydrodynamics 74

8.1 Basic Considerations 74

8.2 Derivation of the HD Equations 76

8.3 The Pressure Tensor 79

8.4 Pressure Variation in Uniform Dilatations 82

8.5 Shear Flow 85

8.6 Effects of Collisions 86

8.7 Off-diagonal Terms and Viscosity 89

8.8 Summary 91

Chapter 9: Magnetohydrodynamics 92

9.1 Basic Considerations 92

9.2 Diffusion and Dissipation 96

9.3 Application of Magnetic Diffusion 98

9.4 Discussion 101

9.5 Partially Ionized Gases 102

9.6 An Electric Current to Satisfy Ampere 108

9.7 Particle Motion Along B 114

9.8 Time-varying Magnetic Field 119

9.9 Comments 121

Chapter 10: Singular Properties of the Maxwell Stress Tensor 123

10.1 Magnetic Equilibrium 123

10.2 Calculation of the Equilibrium Field 128

10.3 Equilibrium in Stretched Field 129

10.4 Resolving the Contradiction 132

10.5 Formation of TDs 133

10.6 Rapid Reconnection at an Incipient TD 137

10.7 Quasi-steady Dissipation at a TD 142

Chapter 11: Comments 147

11.1 Summary 147

11.2 Electric Circuit Analogy 148

11.3 A Simple Example of an Electric Circuit 149

11.4 Popular Electric and Magnetic Fields 154

Appendix A Electrostatically Driven Expansion of the Universe 157

Appendix B Relaxation of Electric Charge Inhomogeneity 159

Appendix C Imposition of a Large-scale Electric Field 162

Appendix D Electric Charge Density in an Electric Field 165

Appendix E The Transverse Invariant 167

Appendix F Blocking the Flow of Electric Current 169

References 173

Index 179