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Title of Thesis

Noor Muhammad Sheikh
Institute/University/Department Details
University Of Engineering & Technology/Electrical Engineering
Not Given
Electrical Engineering
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
aeros-satellites, f2-layer, half-thickness, electron densities, ccir numerical map, aeronomy

F2-layer peak electron densities were derived from the in-situ measurements of electron density by the 'Impedance Probe' and the 'Retarding Potential Analyzer' experiments on board the AEROS-A and B satellites. Bent’s ionospheric profiles were used for height reduction. Global latitudinal and longitudinal variations of the peak density are given at two fixed local times.

Comparisons are made with the predictions from the existing CCIR numerical map. Within the accuracy in the height reduction procedure, the agreement is found to be good over the continental areas, but important differences are observed over the oceans. The longitudinal variations are in general larger then given in the CCIR model. At mid-latitudes and at the equator, the trend of the CCIR longitudinal variation is maintained rather well, but at high and lower latitudes, the differences are large. In the southern hemisphere, the form of the variations is not correctly reproduced and over the oceans, particularly over the pacific, differences of the order of 100 % do occur. In the South Atlantic Anomaly region, latitudinal gradients larger than those given by the CCIR model are shown to exist and the values of the electron densities at night are higher than proposed by the CCIR map.

Other models such as that of CHING and CHIU are shown to produce even larger over-smoothing of the important latitudinal and longitudinal trends and are therefore worse than the CCIR compilation, which at present seems to be the best available. Global model for day and night are given using a similar. Set of mathematical functions as used in the development of the, CCIR numerical maps, but using the local time instead of the universal time. Suggestions are made for improvements in the CCIR numerical maps.

The height of the peak of the F2-layer is an important parameter and also plays a critical role when deriving peak densities from in-situ measurements. A critical review is made of the existing models of the peak height and an improved global model compatible with satellite and incoherent-scatter data is given.

The present work attempts to make a step forward in the field of Aeronomy and Radio Propagation. New results about the longitudinal variations on a global basis based on satellite observations were found. The earlier techniques could not investigate such features because ground stations were practically absent over the oceanic regions.

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2358.15 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
50.12 KB
2 1 Introduction 1
44.6 KB
3 2 Characteristics of the AEROS-Satellites 6
156.31 KB
  2.1 Impedance Probe 8
  2.1.1 Theoretical Principle 8
  2.1.2 Principle of Measurement 10
  2.1.3 Data Interpretation 11
  2.2 Retarding Potential Analyzer 11
  2.2.1 Principle of Measurement 12
  2.2.2 Obtaining Electron Density Data from RPA Data 13
  2.3 Figures 15
4 3 Numerical Mapping of the F2-layer 21
132.86 KB
  3.1 Mathematical Formulation of the CCIR Numerical Map 21
  3.2 Choice of main Latitudinal Variable 22
  3.3 Diurnal Variation 23
  3.4 Calculation of Coefficients for Geographic Coordinate Functions 24
  3.5 Effect of "Screen point" Analysis on CCIR Maps 25
  3.6 Ching and Chiu's Ionospheric Model 28
  3.7 Tables 31
  3.8 Figures 33
5 4 Bent's Ionospheric Model and its use in obtaining Peak Densities from in-situ Data 37
296.75 KB
  4.1 Bent's Ionospheric Profile 37
  4.1.1 Profile Functions 38
  4.1.2 F2-layer Critical Frequency, foF2 39
  4.1.3 F2-layer Peak Height, hmF2 39
  4.1.4 Half-thickness, Y m 39
  4.1.5 Half- thickness, Y t 41
  4.1.6 Decay Constants, k 1 , k 2 , k 3 41
  4.2 Comparison with IRI Profile 42
  4.3 Comparison with AEROS-B Data 43
  4.4 Latitudinal Dependence of Profile Parameters 45
  4.5 Some Remarks on using Bent's Model 46
  4.6 Harmonized Bent's Model 47
  4.7 Derivation of Peak Density from in-situ Measurements 49
  4.8 Maximum Error in Height Reduction 50
  4.9 Relationship between f and foF2 53
6 5 Models for the Height of the F2-1ayer Peak 73
262.3 KB
  5.1 Becker's Relation 74
  5.2 Ching and Chiu's Model 75
  5.3 Shimazaki's Relation 76
  5.4 Corrections 77
  5.4.1 Bradley and Dudeney's Correction 77
  5.4.2 Eyfrig's Correction 78
  5.5 Dudeney's Model 78
  5.6 Bent's Relation 79
  5.7 Bilitza's Model 80
  5.8 hmF2 from AEROS-B in-situ Electron Density Data 81
  5.9 Comparisons of Models and Data 83
  5.10 Improved Model 84
  5.11 Nisbet's MK1 Model 85
  5.12 Comparative Remarks 87
  5.13 Figures 89
7 6 Peak Densities from AEROS in-situ Measurements and Comparisons with CCIR Predictions 104
382.38 KB
  6.1 Longitudinal Variation of Peak Density over Four Longitude Ranges 106
  6.2 Long1tudinal Variations at higher Latitudes 108
  6.3 Comparisons with Theoretical Calculations Introducing Effects of Neutral Air Winds 109
  6.4 Density Var1ations at Night 112
  6.5 Longitudinal Variations at Mid-latitudes 115
  6.6 Longitudinal Variations at Low-Latitudes 116
  6.7 Comparison with Ching & Chiu's Model 119
  6.8 Comparison of Results for August 74 and August 75 120
  6.9 Seasonal Variations of Electron Density 120
  6.10 Electron Density in the South Atlantic Anomaly
  6.11 Region 121
  6.12 Figures 124
8 7 Modification of the CCIR Numerical Map 148
329.79 KB
  7.1 Harmonic Analysis in Longitude 148
  7.2 First Modification of the CCIR Map 151
  7.3 Second Modification of the CCIR Map 153
  7.4 Numerical Map in Local Time 156
  7.5 Conclusions 161
  7.6 Tables 163
  7.7 Figures 168
9 8 Acknowledgement 184
187.34 KB
10 9 List of Symbols 185
454.42 KB
11 10 References 186
87.72 KB
12 11 Appendix 187
237.54 KB