From the Times of London ....................................... xv
Preface ...................................................... xvii
Chapter 1 Basic principles of the ionosphere .................... 1
1.1. Introduction ............................................... 1
1.1.1. The ionosphere and radio-wave propagation ........... 1
1.1.2. Why the ionosphere is so different at high
latitude ............................................ 2
1.2. The vertical structure of the atmosphere ................... 4
1.2.1. Nomenclature ........................................ 4
1.2.2. Hydrostatic equilibrium in the atmosphere ........... 5
1.2.3. The exosphere ....................................... 7
1.2.4. The temperature profile of the neutral atmosphere ... 8
1.2.5. Composition ........................................ 10
1.3. Physical aeronomy ......................................... 13
1.3.1. Introduction ....................................... 13
1.3.2. The Chapman production function .................... 15
1.3.3. Principles of chemical recombination ............... 18
1.3.4. Vertical transport ................................. 20
1.4. The main ionospheric layers ............................... 23
1.4.1. Introduction ....................................... 23
1.4.2. The E and Fl regions ............................... 26
1.4.3. The D region ....................................... 31
1.4.4. The F2 region and the protonosphere ................ 37
1.4.5. Anomalies of the F2 region ......................... 39
1.4.6. The effects of the sunspot cycle ................... 44
1.4.7. The F-region ionospheric storm ..................... 46
1.5. The electrical conductivity of the ionosphere ............. 48
1.5.1. Introduction ....................................... 48
1.5.2. Conductivity in the absence of a magnetic field .... 48
1.5.3. The effect of a magnetic field ..................... 48
1.5.4. The height variation of conductivity ............... 50
1.5.5. Currents ........................................... 50
1.6. Acoustic-gravity waves and traveling ionospheric
disturbances .............................................. 52
1.6.1. Introduction ....................................... 52
1.6.2. Theory ............................................. 53
1.6.3. Traveling ionospheric disturbances ................. 57
1.6.4. The literature ..................................... 57
1.7. References and bibliography ............................... 58
Chapter 2 Geophysical phenomena influencing the high-
latitude ionosphere .................................. 61
2.1. Introduction .............................................. 61
2.2. The magnetosphere ......................................... 61
2.2.1. The geomagnetic field .............................. 61
2.2.2. The solar wind ..................................... 63
2.2.3. The magnetopause ................................... 69
2.2.4. The magnetosheath and the shock .................... 71
2.2.5. The polar cusps .................................... 72
2.2.6. The magnetotail .................................... 72
2.3. Particles in the magnetosphere ............................ 73
2.3.1. Principal particle populations ..................... 73
2.3.2. The plasmasphere ................................... 74
2.3.3. The plasma sheet ................................... 78
2.3.4. Trapped particles .................................. 78
2.3.5. The ring current ................................... 84
2.3.6. Birkeland currents ................................. 85
2.4. The dynamics of the magnetosphere ......................... 86
2.4.1. Circulation patterns ............................... 86
2.4.2. Field merging ...................................... 90
2.4.3. Magneto spheric electric fields .................... 91
2.4.4. The dynamics of the plasmasphere ................... 92
2.5. Magnetic storms ........................................... 93
2.5.1. Introduction ....................................... 93
2.5.2. The classical magnetic storm and the Dst index ..... 94
2.5.3. Magnetic bays at high latitude; the auroral
electrojet ......................................... 95
2.5.4. Magnetic indices ................................... 96
2.5.5. Great magnetic storms and a case history .......... 100
2.5.6. Wave phenomena of the magnetosphere ............... 103
2.6. Ionization by energetic particles ........................ 105
2.6.1. Electrons ......................................... 105
2.6.2. Bremsstrahlung X-rays ............................. 106
2.6.3. Protons ........................................... 107
2.7. References and bibliography .............................. 109
Chapter 3 Fundamentals of terrestrial radio propagation ....... 113
3.1. Introduction ............................................. 113
3.2. Electromagnetic radiation ................................ 113
3.2.1. Basics of line-of-sight propagation in vacuo ...... 113
3.2.2. Principles of radar ............................... 116
3.2.3. The significance of the refractive index .......... 118
3.2.4. Interactions between radio waves and matter ....... 121
3.3. Propagation through the neutral atmosphere ............... 122
3.3.1. The refractivity of the neutral atmo sphere ....... 122
3.3.2. Terrain effects ................................... 124
3.3.3. Noise and interference ............................ 127
3.4. Ionospheric propagation .................................. 140
3.4.1. Magnetoionic theory ............................... 140
3.4.2. Reflection of radio waves from an ionospheric
layer ............................................. 144
3.4.3. Relations between oblique and vertical
incidence ......................................... 149
3.4.4. Trans-ionospheric propagation ..................... 147
3.4.5. Principles of radio scintillation ................. 152
3.4.6. Propagation involving reflection from a sharp
boundary and full-solutions ....................... 159
3.4.7. Whistlers ......................................... 167
3.5. Ionospheric scatter ...................................... 169
3.5.1. Coherent scatter .................................. 169
3.5.2. Forward scatter ................................... 171
3.5.3. Incoherent scatter ................................ 171
3.6. HF-propagation-prediction programs ....................... 174
3.7. Summary .................................................. 175
3.8. References and bibliography .............................. 176
Chapter 4 Radio techniques for probing the ionosphere ......... 181
4.1. Introduction ............................................. 181
4.2. Ground-based systems ..................................... 181
4.2.1. Ionosondes ........................................ 181
4.2.2. Coherent oblique-incidence radio-sounding
systems ........................................... 187
4.2.3. Incoherent-scatter radars ......................... 203
4.2.4. D-region absorption measurements .................. 203
4.2.5. Ionospheric modification by HF transmitters ....... 210
4.3. Space-based systems ...................................... 214
4.3.1. A history of Earth-satellite and radio-rocket
probing ........................................... 214
4.3.2. Basic principles of operation and current-
deployment of radio-beacon experiments ............ 215
4.3.3. Topside sounders .................................. 216
4.3.4. In situ techniques for satellites and rockets ..... 216
4.3.5. Capabilities and limitations ...................... 217
4.4. Other techniques ......................................... 217
4.4.1. HF spaced-receiver and Doppler systems ............ 217
4.4.2. The HF Doppler technique .......................... 218
4.4.3. Ionospheric imaging ............................... 219
4.5. Summary .................................................. 220
4.6. References and bibliography .............................. 221
Chapter 5. The high-latitude F region and the trough .......... 227
5.1. Circulation of the high-latitude ionosphere .............. 227
5.1.1. Introduction ...................................... 227
5.1.2. Circulation patterns .............................. 228
5.2. The behavior of the F region at high latitude ............ 234
5.2.1. The F region in the polar cap ..................... 234
5.2.2. The effect of the polar cusps ..................... 237
5.2.3. The polar wind .................................... 239
5.2.4. The F layer in and near the auroral oval .......... 240
5.3. Irregularities of the F region at high latitude .......... 242
5.3.1. Introduction ...................................... 242
5.3.2. Enhancements: patches, and blobs .................. 244
5.3.3. Scintillation-producing irregularities ............ 249
5.4. The main trough .......................................... 260
5.4.1. Introduction ...................................... 260
5.4.2. Observed properties and behavior of the main
trough ............................................ 261
5.4.3. The poleward edge of the trough ................... 269
5.4.4. Motions of individual troughs ..................... 271
5.4.5. Mechanisms and models ............................. 273
5.5. Troughs and holes at high latitude ....................... 276
5.6. Summary .................................................. 280
5.7. References and bibliography .............................. 281
Chapter 6. The aurora, the substorm, and the E region ......... 285
6.1. Introduction ............................................. 285
6.2. Occurrence zones ......................................... 286
6.2.1. The auroral zone and the auroral oval ............. 286
6.2.2. Models of the oval ................................ 288
6.3. The auroral phenomena .................................... 291
6.3.1. The luminous aurora ............................... 291
6.3.2. The distribution and intensity of the luminous
aurora ............................................ 291
6.3.3. Auroral spectroscopy .............................. 302
6.3.4. Ionospheric effects ............................... 302
6.3.5. The outer precipitation zone ...................... 305
6.4. The substorm ............................................. 308
6.4.1. History ........................................... 308
6.4.2. The substorm in the aurora ........................ 308
6.4.3. Ionospheric aspects of the substorm ............... 311
6.4.4. Substorm currents ................................. 312
6.4.5. The substorm in the magnetosphere ................. 315
6.4.6. The influence of the IMF and the question of
substorm triggering ............................... 319
6.4.7. Relations between the storm and the substorm ...... 321
6.5. The E region at high latitude ............................ 322
6.5.1. Introduction ...................................... 322
6.5.2. The polar E layer ................................. 323
6.5.3. The auroral E layer under quiet conditions ........ 323
6.5.4. The disturbed auroral E layer ..................... 323
6.5.5. Auroral radar ..................................... 326
6.5.6. Auroral infrasonic waves .......................... 330
6.5.7. The generation of acoustic gravity waves .......... 331
6.6. Summary and implications ................................. 332
6.7. References and bibliography .............................. 333
Chapter 7. The high-latitude D region ......................... 337
7.1. Introduction ............................................. 337
7.2. Auroral radio absorption ................................. 339
7.2.1. Introduction history and technique ............. 339
7.2.2. Typical auroral-absorption events and their
temporal and spatial properties ................... 340
7.2.3. General statistics in space and time .............. 350
7.2.1. Dynamics .......................................... 354
7.2.5. The relation to geophysical activity, and
predictions of auroral absorption ................. 365
7.2.6. The wider geophysical significance of auroral-
absorption events ................................. 371
7.3. The polar-cap event ...................................... 382
7.3.1. Introduction ...................................... 382
7.3.2. Observed properties of PCA events ................. 384
7.3.3. The relation to solar flares and radio
emissions ......................................... 389
7.3.4. Effects arising during the proton's journey
to Earth .......................................... 390
7.3.5. Non-uniformity and the midday recovery ............ 395
7.3.6. Effects in the terrestrial atmosphere ............. 398
7.4. Coherent scatter and the summer mesospheric echo ......... 406
7.5. Summary and implications ................................. 409
7.6. References and bibliography .............................. 411
Chapter 8. High-latitude radio propagation: part 1 -
fundamentals and early results ..................... 417
8.1. Introduction ............................................. 417
8.2. ELF and VLF propagation .................................. 419
8.3. LF and MF propagation .................................... 429
8.4. HF propagation ........................................... 439
8.4.1. Tests carried out between Alaska and
Scandinavia on fixed frequencies .................. 439
8.4.2. Tests involving transmission between Alaska and
the continental USA ............................... 448
8.4.3. Other trans-polar HF experiments on fixed
frequencies ....................................... 456
8.4.4. College-Kiruna absorption studies at fixed
frequencies ....................................... 457
8.4.5. Effects of auroral-zone-absorption events on
HF propagation .................................... 473
8.4.6. Sweep-frequency experiments ....................... 473
8.4.7. Other results from HF high-latitude studies
from с. 1956-1969 ................................. 479
8.4.8. Doppler and fading effects on HF high-latitude
propagation paths ................................. 492
8.5. VHF/UHF and microwave propagation ........................ 529
8.6. Summary .................................................. 531
8.7. References and bibliography .............................. 532
Chapter 9. High-latitude radio propagation: part 2 -
modeling, prediction, and mitigation of problem .... 537
9.1. Introduction ............................................. 537
9.2. Ionospheric ray-tracing, modeling, and prediction of
propagation .............................................. 538
9.2.1. Ionospheric ray-tracing ........................... 538
9.2.2. Realistic high-latitude models .................... 538
9.2.3. Validation of ionospheric models .................. 545
9.2.4. The performance of ELP-HF predictions at high
latitudes ......................................... 546
9.2.5. Recent validation of selected ionospheric
prediction models using HF propagation data ....... 553
9.3. Predictions of VHF/UHF propagation ....................... 568
9.4. Recent efforts at validation of ionospheric
models ................................................... 568
9.5. Mitigation of disturbance of HF propagation .............. 572
9.5.1. Early attempts .................................... 572
9.5.2. Mitigation using solar-terrestrial data ........... 572
9.5.3. Adaptive H F techniques ........................... 574
9.5.4. Realtime channel evaluation ....................... 580
9.5.5. Recent advances in assessment of HF high-
latitude propagation channels ..................... 586
9.6. Other high-latitude propagation phenomena and
evaluations .............................................. 591
9.6.1. Large bearing errors on HF high-latitude paths .... 591
9.6.2. Effects of substorm on auroral and subauroral
paths ............................................. 593
9.6.3. Use of GPS/TEC data to investigate HF auroral
propagation ....................................... 594
9.6.4. The performance of HF modems at high latitude
using multiple frequencies ........................ 597
9.7. Summary and discussion ................................... 597
9.8. References and bibliography .............................. 607
Appendix: some books for general reading ...................... 612
Index ......................................................... 613
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