Preface ...................................................... xiii
1. Introductory and Background Material ........................ 1
1.1. Scope and Goals of the Text ........................... 1
1.1.1. Historical Perspective ........................ 1
1.1.2. Organization and Limitations .................. 2
1.2. Structure of the Neutral Atmosphere and the Main
Ionosphere ............................................ 4
1.3. D-Region Fundamentals ................................ 10
1.4. The Earth's Magnetic Field and Magnetosphere ......... 16
References ................................................. 25
2. Fundamentals of Atmospheric, Ionospheric, and
Magnetospheric Plasma Dynamics ............................. 27
2.1. The Basic Fluid Equations ............................ 27
2.1.1. Conservation of Mass ......................... 28
2.1.2. Equation of State ............................ 31
2.1.3. Momentum Equation for the Neutral Fluid ...... 31
2.1.4. Momentum Equations for the Plasma ............ 35
2.1.5. The Complete Equation Sets ................... 36
2.2. Steady-State Ionospheric Plasma Motions Due to
Applied Forces ....................................... 39
2.3. Generation of Electric Fields ........................ 47
2.4. Electric Field Mapping ............................... 48
2.5. Elements of Magnetospheric Physics ................... 54
2.5.1. The Guiding Center Equations and the
Adiabatic Invariants ......................... 54
2.5.2. Magnetohydrodynamics ......................... 61
2.6. Are Ionospheric Electric Fields Real? ................ 68
2.7. Coordinate Systems ................................... 69
References ................................................. 70
3. Dynamics and Electrodynamics of the Equatorial Zone ........ 71
3.1. Motions of the Equatorial F Region: The Database ..... 71
3.2. The Equatorial F-Region Dynamo ....................... 76
3.3. E-Region Dynamo Theory and the Daytime Equatorial
Electrojet ........................................... 89
3.4. Further Complexities of Equatorial Electrodynamics ... 99
3.4.1. The Prereversal Enhancement .................. 99
3.4.2. High-Latitude Effects on the Equatorial
Electric Field .............................. 102
3.5. Feedback Between Electrodynamics and Thermospheric
Winds ............................................... 113
3.6. Mesospheric and Lower Thermospheric Dynamics ........ 119
3.6.1. Atmospheric Winds in the Mesosphere and
Lower Thermosphere .......................... 119
3.6.2. A Primer on Turbulence and the Turbopause ... 122
References ................................................ 125
4. Equatorial Plasma Instabilities and Mesospheric
Turbulence ................................................ 131
4.1. F-Region Plasma Instabilities: Observations ......... 131
4.2. Development and Initiation of Convective
Equatorial Ionospheric Storms (a.k.a. Equatorial
Spread F) ........................................... 142
4.2.1. Linear Theory of the Rayleigh-Taylor
Instability ................................. 142
4.2.2. The Generalized Rayleigh-Taylor Process:
Electric Fields, Neutral Winds, and
Horizontal Gradients ........................ 149
4.2.3. The Seeding of Convective Ionospheric
Storms by Gravity Waves ..................... 152
4.2.4. Role of Velocity Shear in Convective
Ionospheric Storms .......................... 158
4.2.5. Summary of Linear Theory Results ............ 159
4.3. Nonlinear Theories of Convective Ionospheric
Storms .............................................. 160
4.3.1. Two-Dimensional Computer Simulations ........ 160
4.3.2. Simulations Including Seeding and Shear ..... 164
4.3.3. Summary of Nonlinear Theory Results ......... 168
4.4. Linkage of Large and Small Scales in CEIS ........... 169
4.4.1. Evidence for a Diffusive Subrange ........... 169
4.4.2. The Diffusive Subrange ...................... 171
4.4.3. Toward a Unified Theory for the Convective
Equatorial Ionospheric Storm Spectrum ....... 173
4.5. Convective Equatorial Ionospheric Storm Summary ..... 174
4.6. E-Region Plasma Instabilities: The Observational
Data Base ........................................... 175
4.7. Linear Theories of Electrojet Instabilities ......... 187
4.8. Nonlinear Theories of Electrojet Instabilities ...... 200
4.8.1. Two-Step Theories for Secondary Waves ....... 200
4.8.2. On the Observations That the Phase
Velocity of Type I Equatorial Waves
Is Independent of Angle ..................... 202
4.8.3. Nonlinear Gradient Drift Theories ........... 203
4.8.4. Nonlinear Studies of Farley-Buneman (FB)
Waves ....................................... 207
4.9. D-Region Turbulence ................................. 211
4.10. Future Directions ................................... 213
References ................................................ 213
5. Hydro- and Electrodynamics of the Midlatitude
Ionosphere ................................................ 221
5.1. Introduction to the Tropical and Midlatitude
Ionospheres ......................................... 221
5.1.1. Background Material ......................... 221
5.1.2. On the Height of the Daytime F2 Layer ....... 226
5.1.3. Equations Including Vertical Flux Without
Winds or Electric Fields .................... 227
5.1.4. F-Layer Solutions with Production,
Diffusion, and Flux ......................... 229
5.1.5. More General Nighttime Solutions ............ 230
5.1.6. The Appleton Anomaly: An Equatorial
Electric Field Effect ....................... 232
5.1.7. The Corotation Electric Field and
Formation of the Plasmasphere ............... 234
5.2. Electric Fields in the Tropical and Midlatitude
Zone ................................................ 237
5.2.1. Electric Field Measurements ................. 237
5.2.2. Neutral Wind Effects ........................ 242
5.2.3. Combined Effects of Electric Fields and
Neutral Winds ............................... 244
5.2.4. Complexities of the Real Nighttime
Tropical Ionosphere ......................... 245
5.2.5. The Transition Zone Between Mid- and High
Latitudes ................................... 254
5.3. Midlatitude Lower Thermosphere Dynamics ............. 256
5.3.1. Tidal Effects ............................... 256
5.3.2. Wind Profiles ............................... 261
References ................................................ 264
6. Waves and Instabilities at Midlatitudes ................... 267
6.1. Mesoscale Vertical Organization of Ionospheric
Plasma: General Considerations ...................... 267
6.2. Oscillations of the Neutral Atmosphere .............. 268
6.3. Role of Gravity Waves and Tides in Creating
Vertical Ionospheric Structure ...................... 279
6.4. Effects of Particle Precipitation at Midlatitudes ... 286
6.5. Horizontal Structure in the Midlatitude
Ionosphere .......................................... 289
6.6. Midlatitude F-Region Plasma Instabilities ........... 293
6.6.1. F-Region Plasma Instabilities in the
Equatorial Anomaly (Equatorial Arc)
Region ...................................... 293
6.6.2. Local Midlatitude F-Region Plasma
Instabilities: A New Process ................ 302
6.6.3. Linear Theory for the Perkins Instability ... 308
6.7. Midlatitude E-Region Instabilities .................. 312
6.7.1. Radiowave Observations of Nighttime
Midlatitude E-Region Instabilities .......... 312
6.7.2. Multiexperimental Observations of
Midlatitude Structures ...................... 319
6.7.3. Midlatitude E-Region Instabilities:
Difficulties with Simple Explanations ....... 321
6.7.4. The Effect of a Wind Shear: The Kelvin-
Helmholtz Instability as a Source of
Q-P Echoes .................................. 323
6.7.5. The Role of Horizontal Structure:
Amplification by the Cowling Effect ......... 324
6.7.6. Spontaneous Structuring by the Ј5-Layer
Instability ................................. 328
6.7.7. Coupling of Es Layers and the F Layer ....... 330
6.7.8. The Wavelength Limiting Effect and Small-
Scale Instabilities ......................... 333
6.7.9. Wind-Driven Thermal Instabilities ........... 334
References ................................................ 336
7. Dynamics and Electrodynamics of the Mesosphere ............ 343
7.1. Noctilucent Clouds (NLC) and the Solstice
Temperature Anomaly ................................. 343
7.2. Gravity Wave Breaking ............................... 346
7.3. The Polar Summer Mesosphere: A Wave-Driven
Refrigerator ........................................ 348
7.4. New Observations of NLC and Related Phenomena ....... 350
7.5. Polar Mesosphere Summer Echoes (PMSE) ............... 353
7.6. The Role of Charged Ice ............................. 360
7.7. On the Possible Relationship Between PMSE, NLC,
and Atmospheric Change .............................. 362
7.8. Upward-Propagating Lightning ........................ 363
7.9. Nonlinear Mesospheric Waves ......................... 366
7.9.1. Observations ................................ 366
7.9.2. Analogy to a Hydraulic Jump ................. 368
7.9.3. Nonlinear Simulation of Mesospheric Bores ... 369
References ................................................ 373
8. High-Latitude Electrodynamics ............................. 379
8.1. Electrical Coupling Between the Ionosphere,
Magnetosphere, and Solar Wind ....................... 379
8.1.1. General Relationships ....................... 379
8.1.2. A Qualitative Description of Convection
for Southward IMF ........................... 381
8.1.3. Energy Transfer ............................. 387
8.1.4. Additional Complexities ..................... 392
8.2. Observations of Ionospheric Convection .............. 395
8.2.1. Observations During Southward IMF ........... 396
8.2.2. Observations During Northward IMF ........... 400
8.3. Simple Models of Convection in the Magnetosphere .... 403
8.3.1. Models for Southward IMF .................... 404
8.3.2. Models for Northward IMF .................... 411
8.4. Empirical and Analytical Representations of
High-Latitude Convection ............................ 412
8.5. Observations of Field-Aligned Currents .............. 417
8.5.1. Current Patterns for a Southward IMF ........ 419
8.5.2. Current Patterns for a Northward IMF ........ 421
8.5.3. Dependence on Magnetic Activity, IMF,
and Season .................................. 422
8.6. Horizontal Currents at High Latitudes ............... 423
References ................................................ 429
9. Ionospheric Response to Electric Fields ................... 433
9.1. Ionospheric Effects of Parallel Plasma Dynamics ..... 433
9.1.1. Ionospheric Composition at High Latitudes ... 433
9.1.2. Hydrodynamic Theory of the Polar Wind ....... 435
9.2. Ionospheric Effects of Perpendicular Plasma
Dynamics ............................................ 440
9.2.1. The Role of Horizontal Transport ............ 440
9.2.2. Ion Heating Due to Collisions ............... 445
9.2.3. Velocity-Dependent Recombination ............ 449
9.2.4. Positive and Negative Ionospheric Storms .... 450
9.3. Electrodynamic Forcing of the Neutral Atmosphere .... 451
9.3.1. J x B Forcing ............................... 451
9.3.2. Global Observations and Simulations ......... 456
9.4. Particle Acceleration in the Topside Ionosphere ..... 459
9.4.1. Parallel Electric Fields in the Upper
Ionosphere .................................. 459
9.4.2. Ion Outflows and Perpendicular Ion
Acceleration ................................ 462
9.5. Summary ............................................. 465
References ................................................ 465
10. Instabilities and Structure in the High-Latitude
Ionosphere ................................................ 469
10.1. Planetary and Large-Scale Structures in the
High-Latitude F Region .............................. 469
10.1.1. Convection and Production as Sources of
Planetary Scale Structure in the High-
Latitude Ionosphere ......................... 470
10.1.2. Some Effects of Plasma Transport and Loss
on the Large-Scale Horizontal Structure of
the Ionosphere .............................. 471
10.1.3. Longitudinal Structures Due to Localized
Sub-Auroral Electric Fields ................. 476
10.1.4. Temperature Enhancements in the Trough and
Stable Auroral Red Arcs ..................... 480
10.1.5. Horizontal Plasma Variations Due to
Localized Plasma Production and Heating ..... 480
10.1.6. Summary 490
10.2. Intermediate-Scale Structure in the High-Latitude
F Region ............................................ 490
10.2.1. The Generalized E x B Instability at High
Latitudes ................................... 490
10.2.2. Turbulent Mixing as an Alternative to
Plasma Instabilities ........................ 499
10.2.3. Diffusion and Image Formation ............... 502
10.3. Small-Scale Waves in the High-Latitude F Region ..... 510
10.4. E-Region Layering at High Latitudes ................. 515
10.5. Plasma Waves and Irregularities in the High-
Latitude E Region: Observations ..................... 516
10.5.1. Radar Observations .......................... 518
10.5.2. Rocket Observations of Auroral Electrojet
Instabilities ............................... 519
10.5.3. Simultaneous Data Sets ...................... 523
10.5.4. Summary ..................................... 526
10.6. Linear Auroral Electrojet Wave Theories ............. 526
10.6.1. The Gradient Drift Instability .............. 528
10.6.2. The Two-Stream Instability and Type 4.
Radar Echoes ................................ 532
10.6.3. Type 3. Radar Echoes: Are They Due to Ion
Cyclotron Waves? ............................ 533
10.6.4. Nonlinear Theories .......................... 536
10.7. Summary ............................................. 538
References ................................................ 538
Index ......................................................... 545
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