Geomagnetic micropulsations with emphasis placed on the properties and interpretation of pearls

Abstract

The thesis can be divided into three somewhat divergent parts, historical, experimental, and theoretical. The first chapter is an attempt to survey the literature concerning all types of micropulsations. A classification scheme is presented which is in agreement with that adopted by the IAGA at Berkeley, California in 1963, though I have retained the older nomenclature. A summary of the known properties of the various types of micropulsations is presented along with a discussion of controversial points. The next four chapters describe the experimental work performed in cooperation with the Boulder laboratories of NBS, and some observations resulting therefrom. In contrast to the first chapter this section is confined exclusively to pearls. Pearls were found to show little correlation with ionospheric and magnetic data. Exception should be made for two riometer absorption events which can possibly be matched against pearl events. As about 60 to 70 per cent of the pearls observed at College and Macquarie can be matched against each other, pearls are considered to occur simultaneously at conjugate points. At College pearls are shown to be polarized in a plane perpendicular to the magnetic field line. The last chapter develops hydromagnetic wave theory as is pertinent to propagation through the upper magnetosphere. The various assumptions used are examined critically to justify their applicability to the upper magnetosphere. It is found that the magnetosphere below 10,000 km cannot be considered uniform for waves in the 1 cps range. Hence, harmonic solutions to the wave equation cannot be used and more elaborate techniques to treat this problem must be developed. It is suggested that pearls are Alfven waves which propagate along field lines to auroral latitudes. These waves then couple to other modes for propagation to lower latitudes.