The Ionosphere

1. Introduction


2. The International Geophysical Year


2.1 Historical


2.2 IGY Program


2.21 Regular World Days (RWD)


2.22 Alerts and Special World Intervals (SWI)


2.23 World Meteorological Intervals (WMI)


2.24 Operations on Specially Designated Days


2.25 Sounding Schedules for Ionospheric Observations


3. Ionospheric Physics


3.1 Introduction


3.11 Electromagnetic Waves


3.12 The Sun


3.13 Atomic Physics


3.14 Geophysics—The Earth and Its Atmosphere


3.2 Ionospheric Structure


3.21 The Ionospheric Regions


3.22 Nomenclature


3.23 Ionized Layer Formation


3.24 Ionization Decay and the Diurnal Variability of the Ionosphere


3.3 Behavior of Radio Waves in Ionized Media


3.31 General Description


3.32 Theory


3.33 Deductions from Equation for Refractive Index


3.34 The Concept of Virtual Height


3.35 Vertical-Incidence Sweep Frequency Soundings


3.4 Effect of the Earth's Magnetic Field


3.41 General Description


3.42 Motion of Charged Particles in a Magnetic Field


3.43 The Expression for Refractive Index in the Presence of a Magnetic Field (Neglecting Collisions)


3.44 Effects of the Geomagnetic Field on h'f Soundings


3.45 The Third Magneto-Ionic Component


3.46 The Lateral Deviation of Radio Waves in the Ionosphere


3.5 Ionospheric Absorption


3.51 General Description


3.52 Absorption Theory


3.53 Deductions from the Theory-Types of Absorption


3.54 Effects of Absorption on h'f Soundings


3.6 Scattering of Radio Waves in the Ionosphere


3.61 General Description


3.62 Spread Echoes


3.63 Sporadic E


3.7 Variability of the Ionosphere


3.71 Diurnal Variation


3.72 Seasonal Variations


3.73 Solar Cycle Variability


3.74 Short-Term Fluctuations


3.75 Ionospheric Storms


3.8 Oblique Incidence Propagation


3.81 General Description


3.82 Theory


3.83 Conversion of Vertical-Incidence h'f Curve to Corresponding Oblique-Incidence Curve


3.84 Transmission Curves


3.85 Transmission Factors


3.9 Methods of True Height Analysis


3.91 Introduction


3.92 Exact Solution Neglecting the Earth's Magnetic Field


3.93 Exact Solutions including the Earth's Magnetic Field


3.94 Approximate Methods of Solution Neglecting Magnetic Field


3.95 Approximate Methods including Effects of the Magnetic Field


3.96 The Effect of Lower Layers


4. Sounding Equipment


4.1 Pulse Measurements-General


4.2 The Typical Ionosonde


4.21 General Description


4.22 Essential Units


4.23 Accuracy and Reliability


4.24 Power Stabilization


4.25 Short Description of Different Ionosondes


4.3 Adjustments of the Ionosonde


4.31 Pulse Generator


4.32 Calibration Checks


4.33 Receiver Gain


4.34 Schedule of Sweeps


4.35 Use of Expanded Height-Scale


4.36 Oscilloscope Adjustments


4.37 Camera Focus Adjustments


4.38 Use of Auxiliary Gear


4.39 Systematic Maintenance Procedure


4.4 Antenna Systems


4.41 General Requirements


4.42 Practical Systems


4.43 Transmission Lines


4.5 Photographic Processing


4.51 Chemicals


4.52 Auxiliary Equipment


4.53 Loading Developing Reels


4.54 Processing


4.55 Time and Temperature Considerations


4.56 Washing and Drying


4.57 Splicing


5. Interpretation of Ionograms


5.1 Introduction


5.2 Selection Op The Fundamental Trace


5.21 Multiples


5.22 Magneto-Ionic Components


5.23 Transitional Phenomena


5.24 Spread Echoes


5.3 Identification of the Layers


5.31 E Region


5.32 F Region


5.33 Sporadic E


5.4 General Problems of Interpretation


5.41 Spread Echo


5.42 Scaling Es Characteristics


5.43 Other Difficulties Common to Most Locations


5.44 Interpretation Problems Peculiar to Middle and Low Latitudes


5.5 High-Latitude Interpretation Problems


5.51 G Condition


5.52 Extra F2-Layer Echo at Night


5.53 Night E


5.54 The Z Trace


5.55 Ionospheric Storms


5.56 Sporadic E at High Latitudes


5.57 Spread Echoes


6. Reduction of Ionograms


6.1 Parameters to Be Scaled


6.2 Scaling Practices


6.21 General


6.22 Selection and Exclusion Rules


6.3 Measurement of Frequency Characteristics


6.31 Critical Frequencies


6.32 Fes, F0es, and F0es


6.33 F-Min


6.4 Characteristic Heights


6.41 Minimum Virtual Height (H')


6.42 Height of Peak (Parabolic Layer) Hp


6.5 Scaling Accuracy for Critical Frequencies and Virtual Heights


6.51 Desirable Accuracy


6.52 Uncertain and Doubtful Values


6.53 Extrapolation


6.6 Transmission Factors


6.7 Descriptive Qualifying Symbols


6.8 Tabulation of Data


6.81 The Daily Tabulation Sheet


6.82 The Monthly Tabulation Sheet


6.83 The F-Plot


6.84 The H-Plot


6.85 The E-Plot


6.86 The Scaling Notes


6.87 The Observing Log


6.88 Punched-Card Systems


6.89 Data for True Height Analysis


6.9 Statistical Treatment of Data


6.91 Types of Averages


6.92 Conventions for Deriving Medians


6.93 Quartile Values


7. Data Quality


7.1 The Equipment


7.11 Indications of Equipment Malfunction Deduced from Ionograms


7.12 Calibrations


7.13 Record of Gain Settings


7.14 Miscellaneous Equipment Notes


7.2 Scaling


7.21 Frequency Characteristics


7.22 Height Characteristics


7.23 Measurement of M-Factors


7.3 Data Reports


8. References

Appendix I Scaling Symbols


1. Symbols Dropped


2. Extended Definitions


3. Symbols with New Definitions


4. Symbols Which Have Been Added


5. Conventions for Descriptive Symbols


6. Complete List of Symbols

Appendix II Sounding Schedules


1. Temperate- and Low-Latitude Stations


2. High-Latitude Stations


3. Timing


4. Schedule on Regular World Days and Special World Intervals


5. Additional Measurements

Appendix III Suggestions for Punched Card Formats

Appendix IV Interchange of Data and Regional World Centers


1. Monthly Station Booklets


2. Reproduction of Ionograms


3. Data to Be Forwarded to Regional Centers

Appendix V Suggestions for Research at Stations


1. Sunrise Effects


2. Sporadic E


3. Echo Amplitude and Absorption Studies


4. Studies of Importance to Magneto-Ionic Theory


5. Special Methods of Data Presentation

Appendix VI Calendar of Regular World Days and Special World Intervals during the International Geophysical Year