AN ANALYSIS OF IQSY METEOR WIND AND GEOMAGNETIC FIELD DATA by EDWARD HAROLD BLISH B.S., Syracuse University (1963) SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 29, 1969 Teo I ) Signature of Author ( Department of Meteorology, 29 September 1969 Certified by 4 Thesis Supervisor 1i 4 Accepted by Departmental Committee on Graduate Students ftWN AN ANALYSIS OF IQSY METEOR WIND AND GEOMAGNETIC FIELD DATA by Edward Harold Blish Submitted to the Department of Meteorology on 29 September 1969 in partial fulfillment of the requirement for the degree of Master of Science ABSTRACT Meteor wind observations at Sheffield, U.K. for forty weekly twenty-four hour periods during the IQSY were harmoni- cally analyzed for their prevailing, solar tidal, and short- period components. Corresponding magnetic field measurements at Hartland, U.K. were similarly analyzed for their harmonic components. The results were compared to other published values and to those of tidal and dynamo theory. Significant linear correlations between the amplitudes and phase angles of the meteor wind and magnetic field harmonic components demonstrate the existence of systematic relationships between the magnetic field and ionospheric wind variations as predicted by the dynamo theory. Significant correlations re- producable by a simple dynamo mechanism were also found between the magnetic activity indices, the magnetic field, and the pre- vailing ionospheric wind components. Ionospheric current densities and electric fields were esti- mated using the overhead Sq approximation, a simplified conduc- tivity model, and the horizontal current-layer dynamo theory equations. The ionospheric dynamo electric field alone was found to be too small to account for the observed quiet-day magnetic field variations inferring that an additional ionos- pheric electric field of possible magnetospheric origin is probably the primary driving force for the ionospheric currents. Thesis Supervisor: Reginald E. Newell Title: Professor of Meteorology TABLE OF CONTENTS I. INTRODUCTION 8 II. DYNAMO THEORY RESEARCH 10 III. DATA SELECTION AND ACQUISITION 17 A. Ionospheric Wind Data 17 B. Magnetic Field Data 19 C. Notation and Units 20 D. Classification of Data 21 IV. DATA PROCESSING 30 A. Meteor Wind Data 30 1. Discussion of methods of harmonic analysis 30 2. Harmonic analysis method used in present study 39 3. Time averaging of harmonically analyzed values 42 B. Magnetic Field Data 44 1. Harmonic analysis 44 2. Magnetic activity indices 47 C. Statistical Methods 48 1. Description 48 2. Application 51 V. RESULTS AND DISCUSSIONS 68 A. Harmonic Analyses 68 1. Amplitudes 68 2. Phase angles 71 B. Harmonic Parameter Correlations 75 1. Amplitudes 76 2. Phase angles 78 C. Momentum Transports 79 D. Meteor Wind and Magnetic Index Correlations 81 VI. DYNAMD THEORY APPLICATION 131 A. Formulation 131 B. Computations 136 C. Results and Discussions 139 VII. CONCLUSIONS 160 VIII. RECOMMENDATIONS 162 BIBLIOGRAPHY 163 ACKNOWLEDGE MENTS 170 LIST OF TABLES 1. Notation and units of meteor wind and electromagnetic 23 variables used in this study. 2. Additional notation for meteor wind and magnetic field 25 harmonic components used in this study. 3. List of data sources for this study. 26 4. Data classification for this study. 27 5. Coding and definition of seasons for this study. 28 6. Seasonal classification of data days for this study. 28 7. Conversion table for K-Indices and amplitudes of the 55 total deviation of the most disturbed magnetic field component from an established Sq variation. 8. Minimum absolute sample correlation coefficient values 55 significantly different from zero for a given sample size. 9. Means and standard deviations for daily meteor wind 89 and magnetic field harmonic amplitudes by season and by magnetic activity. 10. Comparison of mean daily ionospheric tidal amplitudes 96 by season to other published values. 11. Means and standard deviations for daily meteor wind 97 and magnetic field harmonic phase angles by season and by magnetic activity. 12. Comparison of mean daily ionospheric tidal phase angles 99 by season to other published values. 13. Correlation coefficients for daily meteor wind and 100 magnetic field harmonic amplitudes by season and by magnetic activity. 14. Correlation coefficients for daily meteor wind and 106 magnetic field harmonic phase angles by season and by magnetic activity. 15. Mean daily northward meteor wind tidal momentum trans- 108 ports by season. 16. Longitudinal variations in means, standard devia- 109 tions and correlation coefficients of daily sums of K-Indices. (a) all data days (b) undisturbed data days only 17. Latitudinal variations in means, standard devia- 110 tions and correlation coefficients of daily sums of K-Indices. (a) all data days (b) undisturbed data days only 18. Correlation coefficients for daily absolute ratios 111 of meteor wind harmonic amplitudes and daily Kp sums. (a) all data days (b) undisturbed data days only 19. Correlation coefficients for daily meteor wind harmonic 112 amplitudes and daily magnetic field indices. (a) all data days (b) undisturbed data days only 20. Correlation coefficients for daily meteor wind harmonic 113 amplitudes with daily Kp sums by season. LIST OF FIGURES 1. Geographic location of principal data sources. 29 2. Experimental meteor wind velocities and computed fitted 56 curves for a typical data day. 3. Error in meteor wind velocity measurement as a function 57 of the number of meteor echoes used in its computation. 4. Hourly rates of meteor echoes. 58 5. Upper and lower height limits on meteor echoes as a 58 function of meteor radar wavelength. 6. Annual number of meteor echoes as a function of height. 59 7. Hourly mean height of meteor echoes as a function of 60 time of day. 8. Meteor wind components at Sheffield on 14 April 1965. (a) Northwest component 61 (b) Southwest component 62 9. Magnetic field measurements at Hartland on 14 April 1965. (a) Horizontal component 63 (b) Declination 64 (c) Vertical component 65 (d) Northward horizontal component 66 (e) Eastward horizontal component 67 10. Prevailing amplitude of the eastward and northward 114 meteor wind components at Sheffield between August 1964 and August 1965. 11. Harmonic amplitudes of the eastward and northward meteor wind components at Sheffield between August 1964 and August 1965. (a) Diurnal amplitude 115 (b) Semidiurnal amplitude 116 (c) 8-hour period amplitude 117 (d) 6-hour period amplitude 118 12. Harmonic phase angles of the eastward and northward meteor wind components at Sheffield between August 1964 and August 1965. (a) Eastward diurnal phase angle 119 (b) Northward diurnal phase angle 120 12. (continued) (c) Eastward semidiurnal phase angle 121 (d) Northward semidiurnal phase angle 122 (e) Eastward 8-hour period phase angle 123 (f) Northward 8-hour period phase angle 124 (g) Eastward 6-hour period phase angle 125 (h) Northward 6-hour period phase angle 126 13. Harmonic phase angle difference between the eastward and northward meteor wind components at Sheffield between August 1964 and August 1965. (a) Diurnal phase angle difference 127 (b) Semidiurnal phase angle difference 128 (c) 8-hour period phase angle difference 129 (d) 6-hour period phase angle difference 130 14. Diurnal variation of the height-integrated asymmetri- 145 cal conductivity at the equinoxes. 15. Horizontal height-integrated E-region current density on 14 April 1965. (a) Southward component 146 (b) Eastward component 147 16. Mean horizontal height-integrated current density. (a) Southward component 148 (b) Eastward component 149 17. Seasonal mean horizontal dynamo electric field. (a) Southward component 150 (b) Eastward component 151 18. Mean horizontal total electric field. (a) Southward component 152 (b) Eastward component 153 19. Mean horizontal residual electric field. (a) Southward component 154 (b) Eastward component 155 20. Seasonal mean horizontal height-integrated current density. (a) Southward component 156 (b) Eastward component 157 21. Seasonal mean horizontal total electric field. (a) Southward component 158 (b) Eastward component 159 I. INTRODUCTION According to the dynamo theory of the ionosphere as first sug- gested by Stewart (1882) and developed mathematically by Schuster (1908), daily quiet day variations in the earth's magnetic field (Sq) are attributed to small superimposed magnetic fields of ionospheric currents. These currents are induced by daily periodic ionospheric winds as they move electrically conducting air in a thin layer (90-150 km) across the earth's magnetic field lines. Reviews of the dynamo theory and its mathematical formulation can be found in Chapman and Bartels (1940), Chapman (1963), and Sugiura and Heppner (1966). These daily periodic ionospheric winds are believed to consist primarily of diurnal and semidiurnal thermal tidal components. These tides originate in source regions above and below the ionosphere, i.e., atomic oxygen absorption in the thermosphere, water vapor absorption in the troposphere, and ozone absorption in the upper stratosphere (Sugiura, 1968). Thus the Sq variations would depend primarily on four ionospheric factors: (1) the ionospheric motions as forced by solar heating, (2) the anisotropic electrical conductivity of the ionospheric medium as a func- tion of the particle density and the intensity of the ionizing solar radiation, (3) the vertical propagation of tidal modes from their source regions, and (4) the main magnetic field strength and orientation with respect to the motion of the ionospheric particles. The prevailing and irregular ionospheric winds also contribute, but to a lesser extent and in an even more complicated manner (Van Sabben, 1962 and Hines, 1963). In the past the dynamo theory has been used either to derive the magnetic variations from an assumed tidal wind system, (V-,*J formulation), 9. or to derive the effective tidal wind system from the observed magnetic variations, (J-->V formulation). In both methods quite arbitrary assump- tions had to be made concerning the space and time variations of the mag- netic field and of the ionospheric winds, currents, and conductivities.