This volume is based on lectures and discussions presented at a NATO Advanced Study Institute on ELF and VLF Radio Wave Propagation, which was held in Norway April 1974. The study of propagation of electromagnetic waves with frequen cies below 100 kHz has long traditions in ionospheric physics. To-day, this frequency range is still of great importance, both to the physicist, who uses the waves as diagnostic tools to study the earth's environment and to the engineer who exploits the characteris tics of these waves to improve communications, navigation and timing systems. In recent years the active interest in the field has led to very rapid progress in the development of propagation theory as well as in the application of this theory to the solution of practical problems. The intention of the Organizing Committee for this Conference was to bring together theoreticians and experi mentalists working on the various aspects of wave propagation, in order to stimulate a fruitful discussion and exchange of ideas."

Summary of the NATO Advanced Research Workshop on Physical Signatures of Magnetospheric Boundary Layer Processes T A POTEMRA, M I PUDOVKIN, R W SMITH, V M VASYLIUNAS and A EGELAND 451 PREFACE These proceedings are based on the invited talks and selected research reports presented at the NATO Advanced Workshop on "PHYSICAL SIGNATURES OF MAGNETOSPHERIC BOUNDARY LAYER PROCESSES", held at Sundvolden Hotel, Norway, 9.-14.May 1993. The international political and scientific communities have gradually realized that the Earth's environment is more fragile than previously believed. This has led to the establishment of international research programmes directed toward the understanding of "Global Change". The Earth's magnetosphere, "the Earth-space", is a part of our environment, and physical processes in the magnetosphere and coupling between the solar energy stream, the solar wind, and the Earth-space are important in the complete understanding of our environment. Variations in the electromagnetic and particle energy output of the Sun have a significant effect on global changes. The energy transfer mechanisms at the days ide magnetospheric boundary layers and their ionospheric signatures are perhaps even more important to solar terrestrial research than the night-side processes in this connection. The dayside boundary layers and the polar cusps are the Earth's windows to outer space. The present NATO ARW was the latest in a series of conferences focused on dayside magnetospheric phenomena. It is five years since the preceding Workshop on "Electromag netic Coupling in the Polar Clefts and Caps" was held at Lillehammer in September 1988.

This book is an ordered collection of tutorial lectures on the physical processes in the polar upper atmosphere given at the NATO Advanced Study Institute (ASI) on "The Exploration of the Polar Upper Atmosphere" held at Lillehammer, Norway, May 5-16, 1980. The polar cap is an important part of the high latitude atmosphere not only because of circulation and horizontal trans port in the neutral atmosphere and convection in the ionosphere, but also because of its unique energy sources and sinks. In addition, solar wind plasma is led into-the upper atmosphere by the geomagnetic field at the poles, and the polar cap is, as stated by Tutorial Leader Roederer in this volume, "the place where outer space meets earth". The atmosphere at lower latitudes is well-known to the ground-based observer, and the advent of satellite observations was simply the beginning of a new perspective. The exploration of the atmosphere at polar latitudes, however, proceeded in quite the opposite manner, and satellite maps of the polar caps may be compared with a relatively meagre set of ground-based data. Recent efforts to extend the polar observations from the ground have resulted in the need for a review of the physical principles and processes occurring in the polar upper atmosphere. The interdisciplinary nature of these efforts led to the emphasis here on a tutorial program.

These proceedings are based upon the review lectures, the re search talks and the accompanying discussion from the NATO Advanced Study Institute on "The Dynamical and Chemical Coupling of the Neutral and Ionized Atmosphere" held at Spatind, Norway April 12-22, 1977. In recent years, in spite of the many subdivisions of atmospher ic physics it has become clear that a complete understanding of the subject matter requires an interdisciplinary effort of the scien tists working on a variety of atmospheric phenomena. This Advanced Study Institute was organized in order to meet this demand. A number of eminent scientists were invited to review the major subfields in atmospheric physics and expose the areas where the coupling between the neutral and ionized atmosphere is evident. These review papers were supported by current research results. However, the material covered here is by no means complete con sidering the range of subject matter covered by the title. The re sponsibility for this inadequacy lies with the editors and the pro gram committee, rather than with the individual contributors. Oslo, June 1977. B. Grandal J.A. Holtet. PARTICIPANTS Max-Planck-Institute for Nuclear Physics Arnold, F. P.O.Box 1248, D-0069 Heidelberg F.R.G. Bj centsrn, L. Uppsala Ionospheric Observatory S-755 90 Uppsala Sweden The Institute for Mathematical and Physical Brekke, A."

These proceedings are based upon introductory talks, research reports and discussions from the NATO Advanced Workshop on the "Morphology and Dynamics of the Polar Cusp," held at Lillehammer, Norway, 7-12 May, 1984. The upper atmosphere at high latitudes is called the "Earth's win dow to outer space." Through various electrodynamic coupling process es as well as through direct transfer of particles many geophysical effects displayed there are direct manifestations of phenomena occurring in the deep space. The high latitude ionosphere will also exert a feedback on the regions of the magnetosphere and atmosphere to which it is coupled, acting as a momentum and energy source and sink, and a source of particles. Of particular interest are the sections of the near space known as the Polar Cusp. A vast portion of the earth's magnetic field envelope is electrically connected to these regions. This geometry results in a spatial mapping of the magnetospheric pro cesses and a focusing on to the ionosphere. In the Polar Cusps the solar wind plasma has also direct access to the upper atmosphere. The polar regions are thus of extreme importance when it comes to under standing the physical processes in the near space and their effect on our environment. The Introductory Talks given at this workshop provided a common background for discussing and understanding the physics of the Polar Cusp. By this book we will make the information which thus was provid ed to the participants of the workshop accessible to a wider audience."

This book is an ordered collection of tutorial lectures on the physical processes in the polar upper atmosphere given at the NATO Advanced Study Institute (ASI) on "The Exploration of the Polar Upper Atmosphere" held at Lillehammer, Norway, May 5-16, 1980. The polar cap is an important part of the high latitude atmosphere not only because of circulation and horizontal trans port in the neutral atmosphere and convection in the ionosphere, but also because of its unique energy sources and sinks. In addition, solar wind plasma is led into-the upper atmosphere by the geomagnetic field at the poles, and the polar cap is, as stated by Tutorial Leader Roederer in this volume, "the place where outer space meets earth." The atmosphere at lower latitudes is well-known to the ground-based observer, and the advent of satellite observations was simply the beginning of a new perspective. The exploration of the atmosphere at polar latitudes, however, proceeded in quite the opposite manner, and satellite maps of the polar caps may be compared with a relatively meagre set of ground-based data. Recent efforts to extend the polar observations from the ground have resulted in the need for a review of the physical principles and processes occurring in the polar upper atmosphere. The interdisciplinary nature of these efforts led to the emphasis here on a tutorial program."

These proceedings are based upon the review lectures, the re search talks and the accompanying discussion from the NATO Advanced Study Institute on "The Dynamical and Chemical Coupling of the Neutral and Ionized Atmosphere" held at Spatind, Norway April 12-22, 1977. In recent years, in spite of the many subdivisions of atmospher ic physics it has become clear that a complete understanding of the subject matter requires an interdisciplinary effort of the scien tists working on a variety of atmospheric phenomena. This Advanced Study Institute was organized in order to meet this demand. A number of eminent scientists were invited to review the major subfields in atmospheric physics and expose the areas where the coupling between the neutral and ionized atmosphere is evident. These review papers were supported by current research results. However, the material covered here is by no means complete con sidering the range of subject matter covered by the title. The re sponsibility for this inadequacy lies with the editors and the pro gram committee, rather than with the individual contributors. Oslo, June 1977. B. Grandal J.A. Holtet. PARTICIPANTS Max-Planck-Institute for Nuclear Physics Arnold, F. P.O.Box 1248, D-0069 Heidelberg F.R.G. Bj centsrn, L. Uppsala Ionospheric Observatory S-755 90 Uppsala Sweden The Institute for Mathematical and Physical Brekke, A."

This volume is based on lectures and discussions presented at a NATO Advanced Study Institute on ELF and VLF Radio Wave Propagation, which was held in Norway April 1974. The study of propagation of electromagnetic waves with frequen cies below 100 kHz has long traditions in ionospheric physics. To-day, this frequency range is still of great importance, both to the physicist, who uses the waves as diagnostic tools to study the earth's environment and to the engineer who exploits the characteris tics of these waves to improve communications, navigation and timing systems. In recent years the active interest in the field has led to very rapid progress in the development of propagation theory as well as in the application of this theory to the solution of practical problems. The intention of the Organizing Committee for this Conference was to bring together theoreticians and experi mentalists working on the various aspects of wave propagation, in order to stimulate a fruitful discussion and exchange of ideas."

The Earth's magnetosphere is part of our environment, and physical processes in the magnetosphere and coupling between the solar energy stream, the solar wind, and the magnetosphere are important to our understanding of our environment. Variations in the electromagnetic and particle energy output of the Sun have a significant effect on global changes. The energy transfer mechanisms at the dayside magnetospheric boundary layers and their ionospheric signatures may be even more important to solar-terrestrial research than the nightside processes. The dayside boundary layer and the polar cusps are the Earth's windows to outer space.