Preface ....................................................... vii
1. Ancient Solar Astronomy ..................................... 1
1.1. Mythologies about the Sun .............................. 1
1.1.1. In Early Europe ................................. 1
1.1.1.1. Norse .................................. 2
1.1.1.2. England/Ireland/Scotland ............... 3
1.1.2. North America ................................... 5
1.1.2.1. Among the Navajo Indians ............... 5
1.1.2.2. Among the Pueblo American Indians ...... 6
1.1.2.3. Among the Anasazi Indians .............. 6
1.1.3. South America ................................... 7
1.1.3.1. In Aztec Culture ....................... 7
1.1.3.2. In Mayan Civilization .................. 7
1.1.3.3. Among the Inca in Peru ................. 8
1.1.3.4. Among the Mamaiuran Amazon Indian ...... 9
1.1.4. Egypt and the Middle East ....................... 9
1.1.4.1. In Egypt ............................... 9
1.1.4.2. Middle East ........................... 11
1.1.5. Greek and Roman Mythology ...................... 12
1.1.6. In Asia ........................................ 13
1.1.6.1. In India .............................. 13
1.1.6.2. In China, Japan and Korea ............. 14
1.2. Major Ancient Solar Observing Sites ................... 15
1.2.1. In Europe ...................................... 16
1.2.1.1. The Stonehenge ........................ 16
1.2.1.2. In Ireland at Newgrange ............... 18
1.2.1.3. In Ancient Germany .................... 19
1.2.2. In Ancient Egypt ............................... 19
1.2.3. In Ancient Babylon ............................. 21
1.2.4. In the Early Americas .......................... 21
1.2.4.1. Solar Astronomy among Native
American Indians ...................... 21
1.2.4.2. Solar Astronomy among Aztecs .......... 25
1.2.4.3. Solar Astronomy in Maya
Civilization .......................... 26
1.2.5. In Far East - Asia ............................. 26
1.2.5.1. In Ancient China ...................... 26
1.2.5.2. In Early Japan ........................ 27
1.2.5.3. In Early Korea ........................ 27
1.2.6. In Ancient India ............................... 28
1.2.7. Solar Astronomy in the Medieval Period ......... 29
1.2.7.1. Solar Observatories at Maraga, Iran
and Samarkand ......................... 29
1.2.7.2. Solar Observatories in India .......... 30
2. Modern Solar Observatories ................................. 33
2.0. Introduction .......................................... 33
2.1. Ground based Solar Optical Facilities ................. 33
2.1.1. Optical Solar Observatories in North and
South America .................................. 34
2.1.2. Solar Observatories on the European
Continent ...................................... 42
2.1.3. Solar Observatories in Asia-Australia .......... 53
2.2. Solar Radio Observatories ............................. 58
2.3. Current Solar Space Missions .......................... 62
2.3.1. Planned Solar Space Missions ................... 68
3. Structure of Solar Atmosphere .............................. 72
3.1. From the Solar Interior to the Photosphere ............ 72
3.1.1. Hydrostatic Equilibrium in Solar Interior ...... 72
3.1.2. Energy Generation .............................. 76
3.1.2.1. Proton - Proton (p-p) Chain ........... 78
3.1.3. Energy Transport and Solar Model ............... 81
3.1.4. The Neutrino Behavior .......................... 87
3.1.4.1. Neutrino Flux ......................... 87
3.1.4.2. Detection of Solar Neutrino ........... 87
3.1.4.3. The Case of Missing Neutrinos ......... 89
3.1.4.4. Kamiokande and Sudbury Neutrino
Observatory Results ................... 90
3.1.4.5. Solution of the Solar Neutrino
Puzzle ................................ 92
3.2. The Solar Constant - Solar Irradiance ................. 92
3.3. Limb Darkening ........................................ 94
3.3.1. Limb Polarization .............................. 97
3.4. Solar Rotation ........................................ 97
3.4.1. Solar Rotation from Sunspot Tracers ............ 99
3.4.2. Variation of Rotation Rate with Solar Cycle ... 103
3.4.3. Rotation of Photospheric Magnetic Field ....... 108
3.4.4 Rotation in the Solar Interior ................. 108
3.5. Fast and Slow Streams - the Torsional Oscillations ... 111
3.6. Rotation of the Chromosphere and Corona .............. 114
3.6.1. Coronal Rotation from LASCO Observations ...... 116
4. The Quiet Sun ............................................. 117
4.0. Introduction ......................................... 117
4.1. The Quiet Photosphere ................................ 118
4.1.1. Granulation ................................... 118
4.1.1.1. Early Visual Observations ............ 118
4.1.1.2. Early Photographic Observations ...... 119
4.1.1.3. Granules as Convection Cells ......... 121
4.1.1.4. Shape of Granules .................... 121
4.1.1.5. Granule Size, Brightness and
Contrast ............................. 122
4.1.1.6. Evolution and Life-times of
Granules ............................. 124
4.1.1.7. Center-limb Visibility of
Granulation .......................... 125
4.1.1.8. Granule Velocity and Brightness
Variation ............................ 127
4.1.1.9. Granulation and Magnetic Fields ...... 129
4.1.2. Supergranulation .............................. 130
4.1.3. Mesogranulation ............................... 135
4.2. The Quiet Chromosphere ............................... 135
4.2.1. Introduction .................................. 135
4.2.1.1. Early Observations of the
Chromosphere ......................... 136
4.2.1.2. Early Spectroscopic Observations ..... 137
4.2.1.3. Observations of the Flash Spectrum ... 138
4.2.2. Chromospheric Heating and it's Spectrum ....... 139
4.2.2.1. Heating by Turbulent Motion .......... 141
4.2.2.2. Heating by Wave Motion ............... 142
4.2.2.3. Heating by Magnetic Field ............ 144
4.2.2.4. Heating by 5-minute Oscillations ..... 145
4.2.3. Quiet Chromospheric Structure ................. 145
4.2.3.1. Chromosphere on the Disk ............. 145
4.2.3.2. Chromosphere at the Limb -
Spicules ............................. 147
4.2.3.3. Spicules on the Disk ................. 148
4.2.3.4. Evolution of Spicules ................ 150
4.2.4. Quiet Chromospheric Model ..................... 151
4.3. Transition Region .................................... 153
4.4. The Quiet Corona ..................................... 154
4.4.1. Introduction .................................. 154
4.4.2. Coronal Components, Brightness and
Structure ..................................... 155
4.4.3. Coronal Structure ............................. 157
4.4.4. Observations in Short Wavelengths & Coronal
Hole .......................................... 161
4.4.5. Temperature and Density Profile of the
Corona ........................................ 165
4.4.6. Coronal Bright Points ......................... 166
4.4.7. Radio, EUV and X-ray emissions from the
Corona ........................................ 167
4.4.8. Coronal X-ray and Extreme Ultra Violet
Emissions ..................................... 172
4.4.9. Coronal Magnetic Fields ....................... 173
4.4.10.Coronal Heating ............................... 176
5. The Active Sun ............................................ 179
5.0. Introduction ......................................... 179
5.1. Photospheric Activity ................................ 179
5.1.1. Sunspots ...................................... 180
5.1.1.1. Pre-telescopic Observations of
Sunspots ............................. 180
5.1.1.2. Early Telescopic Observations of
Sunspots ............................. 182
5.1.1.3. Evolution of 'Pores' and Single
Sunspots ............................. 184
5.1.1.4. Evolution of Sunspot Groups .......... 187
5.1.2. Sunspot Penumbra .............................. 189
5.1.2.1. Bright Ring around Sunspots .......... 190
5.1.2.2. Motions in Sunspot Penumbrae ......... 191
5.1.2.3. Asymmetric Evershed Flow and
'Flags' in Sunspot Spectra ........... 194
5.1.2.4. Wave Motions in Sunspots ............. 197
5.1.2.5. Proper Motions of Sunspots ........... 198
5.1.3. Structure of Sunspot Umbrae ................... 198
5.1.3.1. Umbral Granules or Dots .............. 198
5.1.3.2. Umbral Light Bridges ................. 199
5.1.4. Bipolar Characteristics of Sunspots ........... 200
5.1.4.1. Magnetic Fields in Sunspots .......... 201
5.1.4.2. Measurements of Sunspot Magnetic
Fields ............................... 202
5.1.4.3. Distribution of Magnetic Fields in
Sunspots ............................. 204
5.1.4.4. Center-limb Variation of Magnetic
Fields in Sunspots ................... 205
5.1.4.5. Variation of Magnetic Field across
a Sunspot ............................ 205
5.1.4.6. Direction of Lines of Force in
Sunspots ............................. 206
5.1.5. Sunspot Models ................................ 206
5.1.5.1. Umbral Model ......................... 207
5.1.5.2. Penumbra Model ....................... 211
5.1.6. Wilson Effect ................................. 211
5.1.7. Life-times, Number and Latitude Variations
of Sunspots ................................... 213
5.2. Faculae .............................................. 216
5.2.1. Photospheric Faculae .......................... 216
5.2.2. Chromospheric Faculae or Flocculi or Plages ... 217
5.3. Chromospheric Activity ............................... 218
5.3.1. Ellerman Bombs - Moustaches ................... 219
5.4. Evolution of Chromospheric Active Regions ............ 221
5.4.1. Magnetic Fields and Chromospheric Flocculi .... 223
5.5. Large Scale Magnetic Fields .......................... 224
5.5.1. Fine Scale and Ephemeral Magnetic Regions ..... 227
5.5.2. Dispersion and Annihilation of Magnetic
Fields ........................................ 229
5.5.3. Polar Magnetic Fields ......................... 229
5.5.4. Migration of Fields ........................... 232
5.5.5. Generation of Magnetic Fields ................. 234
5.6. Solar Prominences and Filaments ...................... 237
5.6.1. Classification of Prominences ................. 238
5.6.2. Filaments ..................................... 241
5.6.3. Quiescent Prominences ......................... 242
5.6.4. Disparition Brusque ........................... 243
5.6.5. Active Prominences ............................ 245
5.6.6. Loop Prominences .............................. 245
5.6.7. Eruptive Prominences .......................... 246
5.6.8. Surges and Sprays ............................. 249
5.7. Support and Stability of Prominences ................. 250
5.8. Solar Flares ......................................... 252
5.8.1. Flare Classification .......................... 253
5.8.2. Temporal Characteristics of Flares ............ 254
5.8.3. Optical Flares ................................ 256
5.8.4. Two Ribbon Flares ............................. 257
5.8.5. Homologous Flares ............................. 259
5.8.6. Filament - Associated Flares .................. 259
5.8.7. Limb Flares ................................... 259
5.8.8. White Light Flares ............................ 260
5.8.9. Flare Associated Phenomena .................... 260
5.8.10.Radio Emission from Flares .................... 266
5.8.11.EUV and X-ray Flare Emissions ................. 268
5.8.12.Gamma Ray Flares .............................. 272
5.8.13.Cosmic Ray and Proton Flares .................. 273
5.8.14.Flare Theories ................................ 273
5.8.15.Flare Energy Build-up ......................... 274
5.8.16.Flare Energy Release .......................... 275
5.8.17.Flare Models .................................. 277
5.9. Coronal Mass Ejection (CME) .......................... 280
5.9.1. Morphology and Development of CMEs ............ 280
5.9.2. Source Regions of CMEs ........................ 283
5.9.3. Mechanism for Generation of CME ............... 283
5.9.4. Driving Mechanism ............................. 284
5.9.5. X-ray Blow Outs (XBO) ......................... 284
6. Observational Techniques .................................. 287
6.1. Evaluating Solar Seeing .............................. 287
6.2. Determination of Fundamental Solar Parameters ........ 289
6.2.1. Solar Parallax and Distance ................... 289
6.2.2. Solar Mass .................................... 290
6.2.3. Solar Diameter, Density and Surface Gravity ... 290
6.2.4. Solar Luminosity L0 ........................... 291
6.2.5. Temperature of the Sun ........................ 292
6.2.5.1. Effective Temperature ................ 292
6.2.5.2. Brightness Temperature ............... 293
6.2.5.3. Color Temperature .................... 294
6.2.5.4. Kinetic Temperature .................. 294
6.2.5.5. Excitation Temperature ............... 295
6.2.5.6. Ionization Temperature ............... 296
6.2.6. Position Determination of Solar Features ...... 296
6.2.6.1. Determining Solar E-W ................ 299
6.2.6.2. Grid Overlay Template Method ......... 302
6.2.6.3. Mathematical Method .................. 303
7. Solar Optical Instrumentation ............................. 307
7.1. Solar Optical Telescopes ............................. 307
7.1.1. Coelostat ..................................... 308
7.1.2. Heliostat and Siderostat ...................... 310
7.1.3. Coronagraph ................................... 313
7.2. Solar Image Guiders .................................. 314
7.2.1. Active Mirrors and Adaptive Optics ............ 315
7.3. Spectrographs ........................................ 317
7.4. Imaging the Sun ...................................... 319
7.4.1. Spectroheliograph ............................. 321
7.4.2. Narrow Band Filters ........................... 323
7.4.2.1. Principle of Lyot Type
Birefringent Filters ................. 323
7.4.2.2. Principle of the Birefringent Sole
Filter ............................... 327
7.4.2.3. Transmitted Intensity through
Birefringent Filter .................. 328
7.4.2.4. Contrast Element ..................... 331
7.4.2.5. Tuning of Birefringent Filters ....... 331
7.4.2.6. Field of View of Filters ............. 334
7.4.2.7. Throughput or Filter Transmission .... 336
7.4.3. Principle of Fabry-Perot (F-P) Filter ......... 337
7.4.3.1. Mica Solid F-P Etalon Filter ......... 340
7.4.3.2. Lithium Niobate Solid F-P Filter ..... 342
7.4.4. Special Purpose Narrow Band Filters ........... 342
7.4.4.1. Magneto-Optical Filter ............... 342
7.4.4.2 Polarizing Michelson Interferometer ... 344
7.4.5. Filter-based Solar Magnetograph ............... 346
8. Solar Eclipses ............................................ 351
8.1. Eclipse Geometry ..................................... 351
8.1.1. Saros Cycle ................................... 354
8.2. Eclipses as Time Keepers ............................. 357
8.3. Solar Corona and Cosmic Magnetism .................... 358
8.4. Scientific Results from Eclipse Observations ......... 360
8.5. Observing a Total Solar Eclipse ...................... 361
8.5.1. Logistic, Site & Weather Conditions etc. ...... 362
8.5.2. Eye Protection ................................ 363
8.5.3. What to Look for .............................. 363
9. Solar Interior and Helioseismology ........................ 366
9.0. Introduction ......................................... 366
9.1. Solar Oscillations ................................... 366
9.1.1. l-v Diagram ................................... 370
9.1.2. Solar Standard Model (SSM) .................... 371
9.1.3. Observations of Solar Oscillations ............ 375
9.1.3.1. Observations from Space .............. 376
9.1.4. Spherical Harmonic Quantum numbers l, m, and
n ............................................. 377
9.2. Salient Results from Helioseismology ................. 379
9.2.1. Tachocline .................................... 380
9.2.2. Helium Abundance .............................. 381
9.2.3. Temperature and Frequency Variation with
Solar Cycle ................................... 381
9.2.4. Back Side View of the Sun ..................... 382
9.2.5. Sunquakes ..................................... 384
9.2.6. Velocity Structure & Rotation in the Solar
Interior ...................................... 385
9.2.7. The Neutrino Puzzle ........................... 386
10. On the Joy of Observing the Sun - A Personal
Experience ............................................... 387
Appendix I. Basic Units, Conversion Factors, Physical and
Astronomical Constants .......................... 389
Appendix II. Glossary ........................................ 391
Appendix III. References ...................................... 418
Appendix IV. Acknowledgement for Illustrations ............... 433
Appendix V. Index ........................................... 436
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