The High-Latitude Ionosphere and its Effects on Radio Propagation (Cambridge Atmospheric and Space Science Series)

The physical properties of the ionized layer in the Earth's upper atmosphere enable us to use it to support an increasing range of communications applications. This book presents a modern treatment of the physics and phenomena of the high latitude upper atmosphere and the morphology of radio propagation in the auroral and polar regions. Chapters cover the basics of radio propagation and the use of radio techniques in ionospheric studies. Many investigations of high latitude radio propagation have previously only been published in Conference Proceedings and organizational reports. This book includes many examples of the behavior of quiet and disturbed high latitude HF propagation. Ample cross-referencing, chapter summaries and reference lists make this book an invaluable aid for graduate students, ionospheric physicists and radio engineers. Cover......Page 1 Half-title......Page 3 Series-title......Page 5 Title......Page 7 Copyright......Page 8 Contents......Page 9 Dedication......Page 18 Preface......Page 19 1.1.1 The ionosphere and radio-wave propagation......Page 23 1.1.2 Why the ionosphere is so different at high latitude......Page 24 1.2.1 Nomenclature......Page 26 1.2.2 Hydrostatic equilibrium in the atmosphere......Page 27 1.2.3 The exosphere......Page 29 Sources......Page 30 Transport......Page 31 Major species......Page 32 Minor species......Page 33 1.3.1 Introduction......Page 35 1.3.2 The Chapman production function......Page 37 1.3.3 Principles of chemical recombination......Page 40 Diffusion......Page 42 1.4.1 Introduction......Page 45 Aeronomy......Page 48 Sporadic-E......Page 49 Aeronomy......Page 53 Diurnal behavior......Page 57 Radio absorption......Page 58 The peak of the F2 layer......Page 59 The protonosphere......Page 60 The phenomena......Page 61 Winds......Page 65 1.4.6 The effects of the sunspot cycle......Page 66 1.4.7 The F-region ionospheric storm......Page 68 1.5.3 The effect of a magnetic field......Page 70 1.5.5 Currents......Page 72 1.6.1 Introduction......Page 74 1.6.2 Theory......Page 75 1.6.4 The literature......Page 79 1.4 The main ionospheric layers......Page 80 1.6 Acoustic-gravity waves and traveling ionospheric disturbances......Page 81 Conference reports......Page 82 2.2.1 The geomagnetic field......Page 83 2.2.2 The solar wind......Page 85 2.2.3 The magnetopause......Page 91 2.2.4 The magnetosheath and the shock......Page 93 2.2.6 The magnetotail......Page 94 2.3.1 Principal particle populations......Page 95 2.3.2 The plasmasphere......Page 96 2.3.4 Trapped particles......Page 100 2.3.5 The ring current......Page 106 2.3.6 Birkeland currents......Page 107 2.4.1 Circulation patterns......Page 108 2.4.2 Field merging......Page 112 2.4.3 Magnetospheric electric fields......Page 113 2.4.4 The dynamics of the plasmasphere......Page 114 2.5.1 Introduction......Page 115 2.5.2 The classical magnetic storm and the Dst index......Page 116 2.5.3 Magnetic bays at high latitude; the auroral electrojet......Page 117 2.5.4 Magnetic indices......Page 118 2.5.5 Great magnetic storms and a case history......Page 122 The aurora, magnetosphere, and solar wind......Page 123 Electric-power distribution......Page 124 Micropulsations......Page 125 Instabilities......Page 126 2.6.1 Electrons......Page 127 2.6.2 Bremsstrahlung X-rays......Page 128 2.6.3 Protons......Page 129 2.2 The magnetosphere......Page 131 2.5 Magnetic storms......Page 132 Books......Page 133 Conference reports......Page 134 3.2.1 Basics of line-of-sight propagation in vacuo......Page 135 3.2.2 Principles of radar......Page 138 A simple propagating wave......Page 140 Propagation in a lossy medium......Page 141 Conductivity......Page 142 3.2.4 Interactions between radio waves and matter......Page 143 3.3.1 The refractivity of the neutral atmosphere......Page 144 3.3.2 Terrain effects......Page 146 3.3.3 Noise and interference......Page 149 The Appleton equation......Page 162 Polarization......Page 163 Reflection at vertical incidence......Page 166 3.4.3 Relations between oblique and vertical incidence......Page 167 3.4.4 Trans-ionospheric propagation......Page 169 Phase effects......Page 170 The Faraday effect......Page 171 Absorption......Page 173 Diffraction by a thin screen of weak irregularities and the concept of the angular spectrum......Page 174 Fresnel-zone effects......Page 176 Indices and simple statistics of scintillation......Page 179 Reflection at a boundary......Page 181 Sub-ionospheric propagation at ELF and VLF......Page 185 3.4.7 Whistlers......Page 189 3.5.1 Coherent scatter......Page 191 3.5.3 Incoherent scatter......Page 193 3.6 HF-propagation-prediction programs......Page 196 3.7 Summary......Page 197 Section 3.3......Page 198 Section 3.4......Page 199 Section 3.5......Page 200 Section 3.6......Page 201 General reading......Page 202 4.2.1 Ionosondes......Page 203 Capabilities and limitations......Page 208 4.2.2 Coherent oblique-incidence radio-sounding systems......Page 209 Basic principles......Page 210 Types of oblique sounders currently in use......Page 212 HF radars......Page 224 4.2.4 D-region absorption measurements......Page 225 The URSI A1a and A1b methods......Page 226 The URSI A2 method......Page 228 Imaging riometry......Page 230 URSI A3a and A3b methods......Page 231 4.2.5 Ionospheric modification by HF transmitters......Page 232 Basic principles......Page 233 Capabilities and limitations of ionospheric-modification techniques......Page 236 4.3.2 Basic principles of operation and current deployment of radio-beacon experiments......Page 237 4.3.3 Topside sounders......Page 238 4.4.1 HF spaced-receiver and Doppler systems......Page 239 4.4.2 The HF Doppler technique......Page 241 4.5 Summary......Page 242 Section 4.2......Page 243 Section 4.3......Page 246 5.1.1 Introduction......Page 249 5.1.2 Circulation patterns......Page 250 The tongue......Page 256 The UT effect......Page 257 5.2.2 The effect of the polar cusps......Page 259 5.2.3 The polar wind......Page 261 5.2.4 The F layer in and near the auroral oval......Page 262 5.3.1 Introduction......Page 264 Patches......Page 266 Blobs......Page 267 Distribution and occurrence......Page 271 The period and depth of fading......Page 274 Spectrum......Page 278 Direct measurements......Page 279 Modeling......Page 280 5.4.1 Introduction......Page 282 Observations......Page 283 A summary of principal properties (northern hemisphere)......Page 285 Formulae for variations with time and magnetic activity......Page 287 Orientation......Page 291 Electron precipitation and the poleward edge......Page 292 5.4.4 Motions of individual troughs......Page 293 The main trough caused by plasma decay......Page 295 Other mechanisms......Page 296 5.5 Troughs and holes at high latitude......Page 298 5.6 Summary and implications......Page 302 5.2 Behaviour of the F region at high latitude......Page 303 5.3 Irregularities of the F region at high latitude......Page 304 5.4 The main trough......Page 305 5.5 Troughs and holes at high latitude......Page 306 6.1 Introduction......Page 307 6.2.1 The auroral zone and the auroral oval......Page 308 6.2.2 Models of the oval......Page 310 6.3.2 The distribution and intensity of the luminous aurora......Page 313 6.3.4 Ionospheric effects......Page 324 The E region......Page 325 X-rays......Page 326 6.3.5 The outer precipitation zone......Page 327 6.4.2 The substorm in the aurora......Page 330 6.4.3 Ionospheric aspects of the substorm......Page 333 6.4.4 Substorm currents......Page 334 6.4.5 The substorm in the magnetosphere......Page 337 Behavior in the tail......Page 338 Various theories......Page 340 The magnetic power of the solar wind......Page 341 The influence of Bz on triggering......Page 342 6.4.7 Relations between the storm and the substorm......Page 343 6.5.1 Introduction......Page 344 6.5.4 The disturbed auroral E layer......Page 345 6.5.5 Auroral radar......Page 348 Observing geometry and occurrence......Page 350 6.5.6 Auroral infrasonic waves......Page 352 6.5.7 The generation of acoustic gravity waves......Page 353 6.6 Summary and implications......Page 354 6.2 Statistical distribution of the aurora......Page 355 6.4 The substorm......Page 356 6.5 The E region at high latitude......Page 357 Conference reports......Page 358 7.1 Introduction......Page 359 7.2.1 Introduction – history and technique......Page 361 7.2.2 Typical auroral-absorption events and their temporal and spatial properties......Page 362 Sharp-onset and spike events at night......Page 363 Daytime spike events......Page 367 Slowly varying events and pulsations......Page 369 Relativistic electron-precipitation events......Page 370 Latitude and longitude distributions......Page 372 The spatial extent......Page 373 The onset and main event in the night sector......Page 376 Motions on the global scale......Page 381 The drift of the pre-onset bay......Page 383 The relation between the bay and the onset......Page 385 Co-rotation......Page 386 A relation to HF radio propagation......Page 387 Calculation of Q(1)......Page 389 The log-normal distribution......Page 391 7.2.6 The wider geophysical significance of auroral absorption events......Page 393 Incoming electron fluxes......Page 395 The onset and dynamics of the substorm......Page 399 Conjugate behavior......Page 401 7.3.1 Introduction......Page 404 Occurrence and duration......Page 406 Variation from month to month......Page 409 7.3.3 The relation to solar flares and radio emissions......Page 411 Effects in interplanetary space......Page 412 Effects in the magnetosphere......Page 414 Midday recovery......Page 417 Upper-atmosphere ionization during a proton event......Page 420 Day–night variation and twilight effects......Page 422 Effects on the neutral-species composition......Page 427 7.4 Coherent scatter and the summer mesopheric echo......Page 428 7.5 Summary and implications......Page 431 7.2 Auroral radio absorption......Page 433 7.3 The polar cap event......Page 436 7.4 Coherent scatter and the polar mesosphere summer echo......Page 437 8.1 Introduction......Page 439 8.2 ELF and VLF propagation......Page 441 8.3 LF and MF propagation......Page 451 8.4.1 Tests carried out between Alaska and Scandinavia on fixed frequencies......Page 461 HF trans-polar propagation data for the maximum of sunspot cycle 19......Page 463 The College–Stanford circuit (basically a mid-latitude path, D=3500 km)......Page 470 The College–Boston circuit (tangential to the auroral oval, D=5300 km)......Page 471 The College–Kiruna circuit (trans-polar, D=5300 km)......Page 472 College–Kjeller and Thule–Kjeller propagation-path analysis (SSN=38.3–80.2)......Page 474 8.4.4 College–Kiruna absorption studies at fixed frequencies......Page 479 The strong PCA event (SSN=155.8)......Page 490 The weak PCA event of 13 May 1960 (SSN=117.0)......Page 491 Thule–College path......Page 495 Auroral-E modes......Page 497 Other winter modes......Page 498 Off-path modes......Page 499 The Andøya–College path (D=5000 km)......Page 500 8.4.7 Other results from HF high-latitude studies from c.1956–1969......Page 501 Auroral-E ionization effects......Page 502 NGC modes......Page 503 Possible ducted modes......Page 511 8.4.8 Doppler and fading effects on HF high-latitude propagation paths......Page 514 8.5 VHF/UHF and microwave propagation......Page 551 8.6 Summary......Page 553 Section 8.1......Page 554 Section 8.3......Page 555 Section 8.4......Page 556 Section 8.5......Page 557 9.1 Introduction......Page 559 9.2.2 Current high-latitude models......Page 560 9.2.3 Validation of ionospheric models......Page 567 Validation of ELF/VLF prediction......Page 568 Validation of HF prediction......Page 569 A description of the PENEX......Page 575 Specific results of the PENEX......Page 580 The Wales–Rock Springs, Pennsylvania path......Page 581 Auroral ovals and DMSP images applied to the PENEX......Page 587 9.4 Recent efforts at validation of ionospheric models......Page 590 9.5.1 Early attempts......Page 594 9.5.2 Mitigation using solar–terrestrial data......Page 595 9.5.3 Adaptive HF techniques......Page 596 9.5.4 Realtime channel evaluation......Page 602 9.5.5 Recent advances in assessment of HF high-latitude propagation channel......Page 608 9.6.1 Large bearing errors on HF high-latitude paths......Page 613 9.6.2 Effects of substorms on auroral and subauroral HF paths......Page 615 9.6.3 Use of GPS/TEC data to investigate HF auroral propagation......Page 616 9.7 Summary and discussion......Page 619 Section 9.2......Page 629 Section 9.4......Page 631 Section 9.6......Page 632 Appendix: some books for general reading......Page 634 Index......Page 635 This book presents a modern treatment of the physics and phenomena of the high latitude upper atmosphere and the morphology of radio propagation in the auroral and polar regions. Chapters cover the basics of radio propagation and the use of radio techniques in ionospheric studies. Many investigations of high latitude radio propagation have previously only been published in Conference Proceedings and organizational reports. This book also includes many examples of the behavior of quiet and disturbed high latitude HF propagation.