Syun-Ichi Akasofu

It has become increasingly clear that the magnetosphere becomes intermittently unstable and explosively releases a large amount of energy into the polar upper atmos phere. This particular magnetospheric phenomenon is called the magnetospheric sub storm. It is manifested as an activity or disturbance ofvarious polar upper atmospheric phenomena, such as intense auroral displays and X-ray bursts. Highly active conditions in the polar upper atmosphere result from a successive occurrence of such an element ary activity, the polar substorm, which lasts typically of order one to three hours. The concept of the magnetospheric substorm and its manifestation in the polar upper atmosphere, the polar substorm, has rapidly crystallized during the last few years. We can find a hint of such a concept in the term 'polar elementary storm' introduced by Kristian Birkeland as early as 1908. However, we are greatly indebted to Sydney Chapman, who established the basic foundation of magnetospheric physics and has led researches in this field during the last half century. Indeed, the terms 'polar magnetic substorm' and 'auroral substorm' were first suggested by Sydney Chapman. The concept of the substorm was then soon extended by Neil M. Brice of Cornell University, and Kinsey A. Anderson and his colleagues at the University ofCaliforrlia, Berkeley, who introduced the term 'magnetospheric substorm'. We owe many of these recent developments in magnetospheric physics to the great international enterprise, the International Geophysical Year (IGY) and subse quent international cooperative effort (IGC, IQSY).

Polar and Magnetospheric Substorms

Y. Kamide

As a star, the sun is continuously emitting an enormous amount of energy 33 into space, up to as much as 3. 9 X 10 erg/ s. This energy emission consists of three modes. Almost all the energy is emitted in the form of the familiar black-body radiation, commonly called sunlight. Although the amount of energy emitted is small, the sun also emits x rays, extreme ultraviolet (EUV), and UV radiations, which are absorbed above the earth's stratosphere. These constitute the second mode of solar energy, separate from the black-body radiation that penetrates the lower layers of the atmosphere. The sun has another important mode of energy emission in which the energy is carried out by charged particles. These particles have a very wide range of energies, from less than I keY to more than I GeV. Because of this wide range, it is convenient to group them into two components: particles with energies greater than 10 keY and the lower-energy particles. The former are generally referred to as solar protons or solar cosmic rays; their emission is associated with active features on the sun. Their interaction with the atmosphere is similar to that of the x ray and EUV radiation. Low-energy particles constitute plasma, a gas of equal numbers of positive and negative particles. Actually, this plasma is the outermost part of the solar atmosphere, namely the corona, which blows out continuously . For this reason, the plasma flow is called the solar wind.

The Solar Wind and the Earth

The Los Alamos Chapman Conference on Magnetospheric Substorms and Related Plasma Processes can be considered the fourth in a series devoted to magnetospheric substorms, after the Moscow (1971), Houston (1972), and Bryce Mountain (1974) meetings. The main motivation for organizing the Los Alamos Conference was that magnetospheric substorm studies have advanced enough to the point of bringing experimenters, analysts and theorists together to discuss major substorm problems with special emphasis on theoretical interpretations in terms of plasma processes. In spite of an extremely heavy schedule from 8:30 A.M. to 10:00 P.M., every session was conducted in an enjoyable and spirited atmosphere. In fact, during one of the afternoons that we had put aside for relaxation, John Winckler led a group of the attendees in a climb to the ceremonial cave of a prehistoric Indian ruin at Bandelier National Monument, near Los Alamos under a crystal blue sky and a bright New Mexico sun. There, they danced as the former dwellers of the pueblo had, perhaps as an impromptu evocation of a magnetospheric event.

Proceedings of the A.G.U. Chapman Conference ‘Magnetospheric Substorms and Related Plasma Processes’ held at Los Alamos Scientific Laboratory, Los Alamos, N.M., U.S.A. October 9–13, 1978

Dynamics of the Magnetosphere

Syun-Ichi Akasofu, Joseph C. Cain and Sydney Chapman

The Magnetic Field of a Model Radiation Belt Numerically Computed

Jack Finch

Jan Curtis

Dr. Akasofu explains the solar-driven electromagnetic forces that produce the phenomenon, concisely sums up the state of auroral science today, and ponders aspects of the aurora still not understood. Secrets of the Aurora Borealis tracks the evolution of auroral research and presents peoples fearful and poetic reactions to the lights, as well as early northern explorers awe-inspired descriptions.

Syun-Ichi Akasofu

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