Bøger af Syun-Ichi Akasofu

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 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.

Man, through intensive observations of natural phenomena, has learned about some of the basic principles which govern nature. The aurora is one of the most fascinating of these natural phenomena, and by studying it, man has just begun to comprehend auroral phenomena in terms of basic cosmic electrodynamic processes. The systematic and extensive observation of the aurora during and after the great international enterprise, the International Geophysical Year (lGY), led to the concept of the auroral substorm. Like many other geophysical phenomena, auroral displays have a dual time (universal- and local-time) dependence when seen by a ground-based observer. Thus, it was a difficult task for single observers, rotating with the Earth once a day, to grasp a transient feature of a large-scale auroral display. Such a complexity is inevitable in studying many geophysical features, in particular the polar upper atmospheric phenomena. However, it was found that their complexity began to unfold when the concept of the auroral substorm was introduced. In a book entitled Polar and Magnetospheric Substorms, the predeces­ sor to this book, I tried to describe the auroral phenomena as completely as possible in terms of the concept of the auroral substorm. At that time, the first satellite observations of particles and magnetic fields during substorms were just becoming available, and it was suggested that the auroral sub storm is a manifestation of a magnetospheric phenomenon called the magnetospheric substorm.

This book describes the history of the progress made in auroral science and magnetospheric physics by providing examples of ideas, controversies, struggles, acceptance, and success in some instances. The author, a distinguished auroral scientist, fully describes his experiences in characterizing and explaining auroral phenomena.

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. 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.

Prominent progress in science is inevitably associated with controversies. This book, which is based on my own experiences as a scientist, describes the history of the progress made in auroral science and magnetospheric physics by providing examples of ideas, controversies, struggles, acceptance, and success in some instances.