The subject of geomagnetic micropulsations has developed extremely rapidly and it is difficult to know when is an appropriate time to pause and assess the sum total of our knowledge-both observational and theoretical. There has in recent years been a tremendous increase in both the quantity and quality of data and also many theoretical ad vances in our understanding of the phenomenon. Undoubtedly there will be further progress in both areas but it seems worthwhile now to review both our knowledge and our ignorance. This book was essen tially completed by the end of April 1969 and tries to give a summary of the subject up to that time. The Earth is enclosed in the magnetosphere, a hollow carved out of the solar wind by the Earth's magnetic field. Above the ionosphere there is a very tenuous thermal plasma of partially ionized hydrogen in diffusive equilibrium with magnetic and gravitational forces, and ener getic protons and electrons that constitute the trapped Van Allen ra diation belts. Throughout this anisotropic and inhomogeneous plasma, natural and man-made electromagnetic energy propagates in a wide variety of modes and frequency bands. This book is concerned with that class of natural signals called geomagnetic micropulsations-short period (usually of the order of seconds or minutes) fluctuations of the Earth's magnetic field.

The purpose of this study is to investigate and, if possible, establish the feasibility of producing artificial geomagnetic micropulsations by using a large horizontal current loop on the ground. Most natural micropulsations appear to be produced by hydromagnetic (hm) waves propagating in the ionosphere and/or the magnetosphere, and the term 'artificial micropulsations' is used to mean artificially produced hm waves with propagation characteristics similar to those of the natural signals. The critical quantity in the generation process for the hm waves is to the amplitude of the magnetic field variation that can be produced in the ionospheric E-region by the ground-based loop. Currents are induced in the conducting earth beneath the loop whenever its current is varied, and these currents have a magnetic field opposing the magnetic field of the loop. If either the conductivity of the earth or the variation frequency is too high the field at E-region heights may be reduced to a level where negligible hm wave amplitudes are produced. The effect of these earth currents is calculated for an assumed single-layer earth and for a wide range of frequencies and earth conductivities. (Author).

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Physical and chemical studies of the earth and planets along with their sur roundings are now developing very rapidly. As these studies are of essentially international character, many international conferences, symposia, seminars and workshops are held every year. To publish proceedings of these meetings is of course important for tracing development of various disciplines of earth and plane tary sciences though publishing is getting fast to be an expensive business. It is my pleasure to learn that the Center for Academic Publications Japan and the Japan Scientific Societies Press have agreed to undertake the publication of a series "Advances in Earth and Planetary Sciences" which should certainly become an important medium for conveying achievements of various meetings to the aca demic as well as non-academic scientific communities. It is planned to publish the series mostly on the basis of proceedings that appear in the Journal of Geomagnetism and Geoelectricity edited by the Society of Terrestrial Magnetism and Electricity of Japan, the Journal of Physics of the Earth by the Seismological Society of Japan and the Volcanological Society of Japan, and the Geochemical Journal by the Geochemical Society of Japan, . although occasional volumes of the series will include independent proceedings. Selection of meetings, of which the proceedings will be included in the series, will be made by the Editorial Committee for which I have the honour to work as the General Editor.

At the sub-auroral-zone latitude (+54 degrees geomagnetic) of the AFCRL field station, geomagnetic micropulsations associated with the auroral oval are observed only during large nighttime disturbances. Hourly amplitudes of the horizontal component of the micropulsations in octave period bands in the 0.5 to 1024 sec period range are used as measures of the activity. Near local midnight, consistently small values are observed with local K indices

Geomagnetism, Volume 4 focuses on the processes, methodologies, technologies, and approaches involved in geomagnetism, including electric fields, solar wind plasma, pulsations, and gravity waves. The selection first offers information on solar wind, magnetosphere, and the magnetopause of the Earth. Discussions focus on magnetopause structure and transfer processes, magnetosphere electric fields, geomagnetically trapped radiation, microstructure of the solar wind plasma, and hydro magnetic fluctuations and discontinuities. The text then examines geomagnetic tail, neutral upper atmosphere, and geomagnetic pulsations and plasma waves in the Earth's magnetosphere. Topics include plasma waves and instabilities in the magnetosphere, waves in a magneto plasma, gravity waves, atmospheric tides, balance equations for mass, momentum and energy, and absorption of solar and particle radiation. The publication takes a look at auroras and physical processes producing magnetosphere substorms and magnetic storms, including aurora theory and morphology, structure of the magnetosphere, and models of magnetosphere substorms. The selection is a valuable source of data for researchers wanting to explore geomagnetism. - Covers upper atmosphere physics, the magnetosphere, and solar wind - Expert team of contributors from all over the world - The fourth volume of the only comprehensive treatise covering all aspects of geomagnetism

During the last week of September 1968, ESRIN (the European Space Research Institute) held the ESRIN-ESLAB Symposium on 'Low-Frequency Waves and Irregularities in the Ionosphere' in Frascati, near Rome. The symposium was attended by about 60 participants, including speakers from most of the ESRO member states, the U.S.A., the U.S.S.R., and Peru. The main topics covered were: (a) observations of ionospheric irregularities by radar scattering, (b) scintillations of satellite signals, (c) geomagnetic micropulsations, and (d) whistlers. Both theoretical and observational aspects were treated. In addition, laboratory results on low-frequency waves in plasmas were discussed, emphasis being given to their possible relevance to low-frequency ionospheric phenomena. Finally, a brief presentation (not included in these proceedings) of the ESRO rocket and satellite program was given by Dr. Pedersen of ESLAB. The symposium provided an exchange of information among workers in closely related fields. It was also valuable in bringing together people whose experience is predominantly in ionospheric observations with others whose field of interest is mainly in plasma physics (theoretical or laboratory) - a combination that seemed particularly appropriate to ESRIN's program and functions.

Physics of Geomagnetic Phenomena, Volume II covers the advances in geomagnetism and the penetrations into the generation of geomagnetic field phenomena. This book is composed of three chapters and begins with a discussion on various types of phenomenal disturbances, such as ionospheric and geomagnetic disturbance, aurora, and storm. The next chapter describes certain aspects of space geomagnetism based on satellite and rocket observations. This chapter also examines the origins of geomagnetic disturbance phenomena. The last chapter surveys the problems connected with studies of geomagnetic storms and auroras, along with a hydromagnetic model of these phenomena. This book will be of value to physicists, theoreticians, and scientists in allied fields of geomagnetism.