Preface

The year 2000 ushered in a major sunspot maximum period. Occurring every eleven years, spectacular sporadic solar outbursts of particles and fields bombard our Earth's space and continue at a high level for several years. In this time of majestic auroras and satellite-destroying magnetic storms, global interest focuses upon the curious Earth magnetism that guides the solar particles, with fields that penetrate our environment and affect our lives.

Earth magnetism has been of public interest for centuries but with the recent onset of the space age, the magnetic field study has become so scientific that the general public often seems to have been excluded from the developments. To remedy this situation, I have written this book for the interested nonscientist. Explanation of magnetism facts and study results will replace mathematics. You will have a personal, guided tour through these Earth field effects in just five chapters.

My purpose for Chapter 1 is to describe some historical details and to refresh our definitions of a few science words that we will need to use in our tour. (If you feel secure about the review topics in this first chapter, just start with the second.) See Figure C.l.

Chapter 2 concerns the more exciting topic of magnetic applications in today's world. Here I introduce you to the ways that natural magnetic fields impact our daily lives—from navigation to high-tech satellites to communications and power supplies. We will discuss how correlations are established and then debunk some popular misconceptions about magnetism. See Figure C.2.

FIGURE C.1 ► NATURE'S MAGNETISM: Guidebook in hand, a tourist starts out on a path through Earth fields as indicated by the multitude of dipole magnetic-field flowers. We see his route through the subject matter of the chapter: atoms, Chinese compass, opposing fields, magnetic-dip instrument, helical windings, and ghosts of patriarchs rising from their tombstones. In the distance are ships and satellites and the big-dipper constellation, all involved in magnetic navigation. Fishy Stuff (Nonsense) is watching nearby in the ocean, ready to misinterpret everything.

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FIGURE C.2 ► VISTAS OF LIVES IN FIELDS: Our tourist finds herself at the center of the Earth's magnetic field effects—amazed by the consequences of magnetism (real and imagined) upon her daily life. These chapter topics are seen dispersed about her on the great Earth dipole field lines of force.

FIGURE C.3 ► SAILING THE MAGNETIC SEAS IN CALM WINDS: Under conditions of calm solar winds, explorer-tourists are aboard ships sailing toward a variety of north poles. Patterns on the successive sails follow the time evolution of the scientific field models. Fishy Stuff (Nonsense) believes that a magnetic mountain exists at the pole, and Bear Facts (Good Science) is worrying about the many pole positions. Both wish to be involved in the trip.

FIGURE C.3 ► SAILING THE MAGNETIC SEAS IN CALM WINDS: Under conditions of calm solar winds, explorer-tourists are aboard ships sailing toward a variety of north poles. Patterns on the successive sails follow the time evolution of the scientific field models. Fishy Stuff (Nonsense) believes that a magnetic mountain exists at the pole, and Bear Facts (Good Science) is worrying about the many pole positions. Both wish to be involved in the trip.

In Chapter 3, our tour visits the deep-Earth source of the principal magnetic field and its surface image. The five different representations of the Earth's magnetic pole positions will be explained. We will also view quiet-time daily variations that are regularly superposed on our main field. Together, the quiet-time "everyday" variation levels and the main field form a "bottom line" from which scientists measure the magnificent geomagnetic storms. Our tour will also include an interesting quiet-time, Earth's polarregion field that gives indirect evidence of the Sun's magnetic field direction. See Figure C.3.

FIGURE C.4 ► UMBRELLA FOR MAGNETIC STORMS: Our tourist tries an umbrella for protection from the bombardment of particles and fields that attend magnetic storms. The destructive solar wind is driven from the Sun to the Earth's protective main magnetic field.

In Chapter 4, our tour follows the spectacular field disturbances that start as blasts of particle ejections from our active Sun. Although such solar-terrestrial storms are of special interest to space scientists and satellite users, these storms can affect the daily lives of all of us who live in modern developed countries. We will examine the storm impact at the Earth, field appearances on magnetic records, and indices of such activity. See Figure C.4.

Chapter 5 ends our tour with questions and answers for those tourists who have developed a curiosity about how the fields are measured, what researched is now in progress, how field records can be obtained, and what books and electronic Web sites are recommended for further information. See Figure C.5.

FIGURE C.5 ► HARVESTING THE FIELDS: Seated at his desk, our tourist has magnetic field questions that can be answered by a display of Web sites on the computer screen or the supply of references on his bookshelf. A picture of Chapman, the modern father of space magnetism, is prominently displayed. Fishy Stuff (Nonsense) has been relegated to the position of a stuffed bookend. Bear Facts (Good Science) is away, waiting for further discoveries by the next generation of researchers.

Now, let us start the tour. Have no fear, I will see that we stay clear of mathematical equations and focus our time on the important ideas about our Earth's magnetism.

W.H.C. November 2000

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