The Earth's Plasmasphere (eBook)

Contents 4
Preface 6
Foreword 8
CLUSTER and IMAGE: New Ways to Study the Earth's Plasmasphere 11
Introduction 12
History of Plasmasphere Data Interpretation 13
Data Interpretation at the Beginning of the Space Age 13
More Refined Space Experiments 16
Radio Probing from Ground and Space 22
Theoretical Understanding 23
The Quest for a More Global View 24
The Rationale of Global Imaging: Image/EUV Observations 24
Radio Observations in Space with Image/RPI 25
Disentangling Spatial and Temporal Variability with Cluster 27
New Data Analysis Tools 28
Analysis of Global Images 28
Overview of Methods 28
Removal of Noise and Instrument Artifacts 28
Photometric Calibration 29
Three-Dimensional Inversion and Projection on the SM Equatorial Plane 29
Density Calibration 30
Comparison of Successive Images 30
Data Accumulation 31
Visualization Aids 31
Correlation with Data from Other Spacecraft or Ground Stations 31
Example: A Technique for Determining Plasmaspheric Drifts 32
Outlook 34
Interpretation of Remote Sounding and Local Radio Observations 34
Remote Sounding 34
Local Plasma Observations 36
Classical Gradient Computation and the Curlometer 41
Principle 41
Error Determination 41
Applications 42
Least-Squares Techniques for Gradient Computation 44
Principle 44
Error Estimates 46
Applications 46
Time-Delay Analysis with Multiple Spacecraft 46
Method 46
Applications 47
Conclusions and Outlook 47
Acknowledgements 49
References 49
Plasmaspheric Density Structures and Dynamics: Properties Observed by the CLUSTER and IMAGE Missions 58
Introduction 59
Before Image and Cluster 59
Image Observations of Density Structures 61
Cluster Observations of Density Structures 62
Outline of the Paper 63
Sources and Losses in the Plasmasphere 64
The Disturbed Plasmasphere: A New Look at Refilling 64
The Quiet Plasmasphere 66
New Evidence for a Plasmaspheric Wind 68
Erosion of the Plasmasphere 68
Overall Plasma Distribution and Plasmapause Position 70
Overall View from EUV 70
Plasma Density in the Plasmasphere 70
Overall Density Gradients in the Plasmasphere 71
The Plasmapause Seen by Cluster 73
Introduction 73
Statistical Study of the Plasmapause Distance 74
Plasmapause Dynamics: Position and Velocity 74
Statistical Study of the Plasmapause Position and Thickness 75
Ion Composition 76
Ion Composition from Image 76
Seasonal Variations 77
New Methods of Studying Ion Composition in the Plasmasphere 77
Ion Composition from Cluster 78
Average Ion Mass from Alfvén Waves 79
Plasmaspheric Plumes 79
Overall Plume Formation 80
Plume Structure and Evolution on Large Scales 81
Complicated Structure 81
Global Visualisation of a Plume Crossing 83
Plume Structures on Small Scales 84
Statistical Analysis of Plasmaspheric Plumes 86
The Plasmasphere-Ionosphere Connection 87
Notches 89
Observations of Notches 90
Departures from Corotation 91
Shoulders, Channels, Fingers, Crenulations 93
Small-Scale Density Irregularities 94
Earlier Work 94
Field-Aligned Density Irregularities 94
Irregular Density Structures in the Outer Plasmasphere 95
Remote Sensing of Density Irregularities by the RPI Instrument 95
Comments on RPI Observations 95
Interpretation of RPI Observations in Terms of Density Structure 96
In situ Observations of Small-Scale Density Structures 97
Morphology 97
Dynamics 98
Occurrence 99
Conclusion 99
Sources and Losses in the Plasmasphere 99
Overall Plasma Distribution and Ion Composition 100
Plasmaspheric Plumes 100
Density Structures at Smaller Scales 101
Perspectives 102
Acknowledgements 102
References 103
Electric Fields and Magnetic Fields in the Plasmasphere: A Perspective from CLUSTER and IMAGE 110
Introduction 111
Whistler Measurements to Derive Convection 111
The Whistler Method of Measuring Cross-L Plasma Drifts 112
Whistler Estimates of the Ey Electric Field Component Near Dusk 114
Measurements on Whistler-Mode Transmitter Signals 114
Cluster and Image Achievements 115
Inner Magnetospheric Electric Fields Measured by CLUSTER 116
EDI Onboard Cluster 117
Inner Magnetospheric Electric Fields 117
Case Studies 117
Statistical Studies on IMF BZ Dependence 119
Statistical Studies on IMF BY Dependence 121
Summary 122
Inner Magnetospheric Electric Fields From Plasmasphere Images 122
Technique for Deducing Electric Fields From Image 122
Phenomenology of the Erosion Process 122
Internal Magnetospheric Electric Fields 123
SAPS Electric Fields 124
DMSP and Image Observation 124
Multi-Spacecraft Observations of SAID: A Cluster Perspective 125
SAID Electric Field 125
SAID Field-Aligned Current 127
Spatial Gradients of the Magnetic Field in the Plasmasphere from CLUSTER 127
Datasets and Analysis Technique 128
A Typical Plasmasphere Crossing 128
Summary and Conclusions 131
Summary and Outlook 132
Acknowledgements 134
References 134
Advances in Plasmaspheric Wave Research with CLUSTER and IMAGE Observations 139
Introduction 140
CLUSTER and IMAGE Wave Instrumentation 142
Cluster Wave Instruments 142
Image Wave Related Phenomena Instruments 142
Kilometric Continuum 143
Previous Observations 143
Image Observations 144
Conclusions 147
Non-Thermal Continuum 149
Cluster Observations 149
Assets of the CLUSTER Mission 149
Typical Spectral Signatures 150
Analysis 153
Beam Stability 153
Beam Geometry 153
Interpretation 156
Main NTC Form (Quasi Equatorial Sources) 156
Close up View on Sources 156
Propagation Effects 157
Wide Banded NTC Emissions 157
Z-Mode 158
Active Z-Mode Experiments in Space Plasmas 158
Z-Mode Sounding from Image 159
Ducted Echoes and the Z-Mode Propagation ``Cavity'' 160
Remote Sensing of Density Profiles Along the Geomagnetic Field Lines Above IMAGE 162
Remote Sensing of Plasma Composition Along the Geomagnetic Field Lines 163
Additional Diagnostics Uses of Z-Mode Echoes 164
Non-Ducted or ``Direct'' Earthward Propagating Z-Mode Echoes 164
Diagnostic Uses of Direct Z-Mode Echoes 164
Scattered Z-Mode Echoes 164
Diagnostic Uses of Scattered Z-Mode Echoes 165
Whistler-Mode Soundings at Altitudes Below 5000 km 166
Spreading of RPI Whistler-Mode Echoes in Time Delay 166
Examples of Magnetospherically Reflected and Specularly Reflected Whistler-Mode Echoes 167
Specularly Reflected Whistler-Mode Echoes 167
Magnetospherically Reflected Whistler-Mode Echoes and the Lower Hybrid Resonance 168
The Diagnostic Potential of Magnetospherically Reflected and Specularly Reflected Whistler-Mode Echoes 168
Proton Cyclotron Echoes and a New Resonance 169
The fce+ Echo 169
The fce+ Resonance 170
Whistler-Mode Proton Cyclotron Echoes 170
Comments on Physical Mechanisms of Proton Cyclotron Echoes 172
Chorus 173
Observations of Whistler-Mode Chorus Emissions by Cluster 173
Position and Size of the Chorus Source Region 173
Propagation of Chorus From its Source Region 174
Hiss 176
Plasmaspheric Hiss 176
Impact on the Radiation Belts 177
Origin of Plasmaspheric Hiss 177
Mid-Latitude Hiss 178
Mid-Latitude Hiss and Auroral Hiss 178
Source Location and Generation Mechanism 179
Geomagnetic Activity Impact 180
Equatorial Noise 180
Introduction 180
Cluster Observations 181
Generation Mechanism of Equatorial Noise and its Effects 183
ULF Resonances 183
Historical Description 183
Image Observations 184
Conclusion 185
Acknowledgements 186
References 187
Recent Progress in Physics-Based Models of the Plasmasphere 194
Introduction 195
The Fluid Approach 196
Inner Magnetospheric Electric Potential 196
Plasmasphere-Ionosphere Coupling 201
Plasmasphere-Magnetosphere Coupling 203
The Kinetic Approach 205
Plasmapause Formation 205
Plasmaspheric Wind 206
The Role of Quasi-Interchange Modes 208
Testing the Instability Criteria of Quasi-Interchange Modes in the Plasmasphere 208
Implications of a Plasmaspheric Wind and Future Refinements 209
Transport of Plasmaspheric Material Caused by Ultra Low Frequency Waves 209
Electric Field in Equilibrium Theory 212
Stationary Density Distribution in the Plasmasphere 212
The Exospheric Equilibrium Density Distributions 214
Physics Model Constrained by Empirical Data 216
Kinetic Process of Plasmaspheric Refilling 217
Coulomb Collisions 217
Monte Carlo Simulations 218
Comparison Between MHD and Kinetic Approaches 219
Time Dependent Models for Field-Aligned Plasma Density Distribution 220
Time Dependent Refilling Model 220
Other Models of the Plasmasphere 221
Conclusions 222
Acknowledgements 223
References 223
Augmented Empirical Models of Plasmaspheric Density and Electric Field Using IMAGE and CLUSTER Data 231
Introduction 232
Empirical Equatorial Density Models 233
Field-Aligned Density Distributions for Plasmasphere and Plasma Trough 235
Field Line Dependence of Electron Density from in Situ Data 235
Field Line Dependence of Mass Density Based on Spacecraft Observations of Alfvén Frequencies 235
Event-Driven Density Model 236
Field-Aligned Dependence from Image RPI Measurements 237
Field-Aligned Density Distributions in the Polar Cap 244
Empirical Models of Electric Field 246
The Corotation Electric Field 246
Empirical Convection Electric Field Models 246
Volland-Stern's and Maynard-Chen's (VSMC) Convection Electric Field Model 247
McIlwain's E5D Convection Electric Field Model 247
Weimer's Convection Electric Field Model 248
Inner Magnetospheric Electric Field (UNH-IMEF) Model 249
Influence of Electric Field Models on the Plasmapause Position Modeling 253
Summary 254
Acknowledgements 255
References 255
Index 262
Bibliography 268