-1- THE CONTROL AND GENERATION OF MAGNETIC PULSATIONS ON THE GROUND AND IN INTERPLANETARY SPACE BY PARAMETERS OF THE SOLAR WIND Timothy Joab Odera Doctor of Philosophy University of Edinburgh 1982 S ;. N 0Cb -11- DECLARATION I hereby declare that the work presented in this thesis is my own and has not been presented for a degree in any other University; and that the thesis has been composed by myself. -111- ABSTRACT There is evidence to suggest that some Pc 3, 4 pulsations are controlled by solar wind parameters. The waves have been thought to originate as low- frequency waves generated within the solar wind. Data from five ground stations and the ISEE-2 satellite have been used in an investigation ofthe problems of the control by solar wind parameters of the generation of low-frequency (10 - 80 mHz) waves in the solar wind and their relationship to Pc 3, 4 pulsations on the ground. The five ground stations form part of the IGS array of rubidium magnetometers operated during the Inter- national Magnetospheric Studies (ThIS). The ground data have been correlated with the 7`-hourly values of the solar wind velocity (Vu), the IMF magnitude (B) and the IMF cone angle ®B• Results from statistical analysis of the ground data indicate that (a) the energy level of Pc 3, 4 pulsations on the ground increases with the increase in swV (b) the energy level rises with the decrease in 0 x (c) the Pc 3 pulsation is better related to the IMF cone angle than the Pc 4 pulsation and (d) the frequency of Pc 3, 14 pulsations depends on the IMF magnitude. The quality of the last relationship is found to be improved when the same frequency of Pc 3, 14 activity is observed over a large area of the Earth's surface. Data from the ISEE-2 satellite have been used to study the characteristics of low-frequency upstream waves. Three classes of waves have been identified. These are (a) continuous pulsations similar in type to Pc, (b) quasi- periodic incoherent oscillations, distinguished by mixed period fluctuations which often last for several hours, and (c) relatively isolated wave 'bundles'. - iv- The upstream waves are observed preferentially when the IMF direction is sunwards, and the waves are 145 0 found to be most common when the cone angle is 150 - For a set of selected events the dependence of the frequency of the upstream waves on the IMF magnitude has been tested, and a functional relationship F = C O + C 1 B, between their frequency and the IMF magnitude has been found to be a statistically better fit to the data than the form F = CB which is in common use. The upstream waves aboard the ISEE-2 spacecraft and the Pc 3, 14 pulsations recorded simultaneously on the ground stations CL = 1.8 - 14.3) have been compared. It is found that similarity of the spectra of the waves in the solar wind and the ground is very rare and that correspondence between the events in space and on the ground is extremely low. It is implied that the pulsations in the two media are generated by two different mechanisms. It is concluded that both satellite and ground pulsations are influenced by the parameters of the solar wind; but. that the waves in the solar wind are not transmitted through the magnetosheath and magnetosphere directly to appear as Pc 3, 14 pulsations observed on the ground. -v- LIST OF CONTENTS Page Title page i Declaration Abstract List of contents v List of tables ix List of captions xi CHAPTER 1 GENERAL INTRODUCTORY NOTES 1 1:1 Introduction 1 1:2 Importance of geomagnetic pulsations 2 1:3 This work 1:1 Geomagnetic pulsations 6 1:4-1 Definition 6 1:1-2 Short historical notes 8 1:14-3 Classification of geomagnetic pulsations 9 CHAPTER 2 THEORETICAL BACKGROUND 13 2:1 Solar wind and Magnetosphere 13 2:1-1 Introduction 13 2:1-2 The solar wind 13 2:1-3 Interplanetary magnetic field (IMF) 114 2:1-14 The magnetosphere and its boundaries 15 2:1-5 The dynamics of the magnetosphere 21 2:2 Origin and transmission of micro- pulsations 23 2:2-1 Introduction 23 2:2-2 Hydromagnetic waves 26 2:2-3 Simplified solutions of the hydro- magnetic equations 32 2:2-14 Generation mechanisms for micro- pulsations 314 2:2-5 Field line resonance 36 Me Page 2:2-6 Solar wind irregularities 141 2:2-7 Wave-particles interactions: plasma instabilities 142 2:2-8 Others 1414 2:2-9 Inospheric and atmospheric trans- mission 1411 CHAPTER 3 OBSERVATIONAL BACKGROUND 1.7 3:1 Solar wind controlled pulsations 147 3:1-1 Introduction 147 3:1-2 Period of Pc 3, 11 pulsations 147 3:1-3 Occurrence and/or amplitude of pulsations 53 3:1-li. Models for solar wind control of Pc 3, ii. pulsations 63 3:2 Observations of Pc 3, 14 in the UK 71 CHAPTER 14 CONTROL OF THE SOLAR WIND PARAMETERS ON THE GROUND Pc 3, 14 PULSATIONS 83 14:1 Introduction 83 )4:2 Data 81.. 14:2-1 Ground data 81.. )4:2-2 Satellite data 90 Analysis and Results 101 li.:3-1 Inter-relation of V , Q and B 101 5W xB 14: 3 General distribution of V , B, -2 sw e xB 106 4:3-3 Geomagnetic pulsations occurrence and variation with local time 107 4:3- 4 Effect of solar wind velocity 109 1i.:3-5 Effect of IMF cone angle 12 14 11:3-6 Effect of IMF magnitude on the frequency of Pc 3, 11 pulsations 151 -vii- Page CHAPTER 5 LOW-FREQUENCY WAVES IN THE INTERPLANETARY MEDIUM 171 5:1 Introduction 171 5:2 Interplanetary magnetic field data selection and processing 178 5:2-1 Introduction 178 5:2-2 Selection procedure 179 5:3 Results 181 5:3-1 Classification of waves in the IMP 181 5:3-2 Period and amplitude of waves in the IMP 188 5:3- 3 Effects of IMP orientation 192 5:3-4 Spectral character of IMP waves 203 CHAPTER 6 CORRELATION OF GROUND AND SATELLITE PULSATIONS 225 6:1 Introduction 225 6:2 Direct comparison 232 6:2-1 High latitude station 232 6:2-2 Mid-latitude station 249 6:3 Statistical comparison 266 CHAPTER 7 SUMMARY, DISCUSSIONS, INTERPRETATIONS AND CONCLUSIONS 271 7:1 Scatter in the E - Vsw relation 271 7:2 Limitation of the use of the cone angle, 274 9x 7:3 Low-frequency waves in the solar wind: summary and discussions 277 7:4 Derived relations, F - B in space and on the ground 292 7:5 Interplanetary origin of Pc 3, it pulsations 294 7:6 What model? 301 -viii - Page 7:7 Summary and conclusions 307 7:8 Suggestions for further work 311 APPENDIX Al 311 ACKNOWLEDGEMENTS 315 REPERECNES 317 -ix- Tables Page 1:1 Periods of geomagnetic variations. 7 1:2 Period ranges of pulsations. 12 3:1 Locations of observations used in the studies of pulsations and solar wind, and quantities that were correlated. 14:1 Recording stations locations. S. 14:2 Orbital parameters of ISEE-2 satellite for different epoch. 01 14:3 Summary: Intreiation of the solar wind parameters. 1014 14:14 Correlation coefficients of the solar wind parameters. 105 11:5 Summary of the EVsw relation. 123 11:6 Summary of the cone angle effect on the pulsation energy. 150 24:7 Summary of the F - B relation of the Pc 3, 14 pulsations on the ground. 159 14:8 Pc 3 regression results. 161 11:9 Regression results of simultaneous events. 1614 5:1 Statistics of Sunward/Antisunward. ThIF in relation to the presence of pulsations in the interplanetary medium. 197 -x- Tables Page 5:2 Summary of result of regression analysis. 218 5:3 Significance test of the slopes and intercepts of the regression lines for the F - B relation. 222 5:11 Significance test: Regression lines forced through origin. 223 7:1 Number of data points. 7:2 Observational relations between solar wind parameters and Pc 3, 4 pulsations. 309 -xi- FIGURE CAPTIONS Figure Caption Page 2:1 The lines of force of the quiet-day inter- planetary magnetic field resulting from extension of the general solar field by an idealized uniform 300 km/sec quiet day solar wind directions (adapted from Parker, 1963). 16 2:2 Schematic view of the magnetosphere in the noon- midnight magnetic meridian, plane (Ness, 1967). 18 2:3 Model of the magnetosphere according to Heikkila (1973). 19 2:4 The symmetry relations at magnetically conju- gate points for oscillation of the lines of magnetic force. H, horizontal component; D, east declination (Sugiura and Wilson, 19614). 33 2:5 Schematic diagram of variation of amplitude and polarization as a function of L for unstable surface wave on the magnetopause coupled to a resonant field line. 39 2:6 Variation of low frequency micropulsation polarization as a function of local time and latitude (Samson et al., 1971). Amplitude is maximum at the lower latitude point (line AB) where polarization changes. 39 3:1 Average interplanetary magnetic field magnitude versus period of magnetic pulsations seen at a mid-latitude observatory (Troitskaya et al., 1972). 49 Figure Caption Page 3:2 Two- versions of the observational results relating the IMF magnitude (B) to the period (T) of daytime pulsations. The curves are drawn from T = 160/B. 0 50 3:3 Histograms of the occurrence of interplanetary field strengths for each level of the Borok-B- index (Russell and Fleming, 1976).