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Cosmic Rays, the Sun and Geomagnetism: The Works of Scott E. Forbush

Cosmic Rays, the Sun and Geomagnetism: The Works of Scott E. Forbush

James A. Van Allen (Editor)

ISBN: 978-1-118-66799-6

Mar 2013, American Geophysical Union

472 pages

Select type: O-Book


Published by the American Geophysical Union as part of the Special Publications Series.

This monograph is a tribute to the character and achievements of Scott Ellsworth Forbush (1904-1984) who, almost single-handedly with only technical assistance, laid the observational foundations for an important part of the subject of solar-interplanetary-terrestrial physics. The heart of his research was the meticulous and statistically sophisticated analysis of the temporal variations of cosmic-ray intensity as measured by ground-based detectors at various latitudes and altitudes.

Forbush either discovered or put on a firm basis for the first time the following fundamental cosmic-ray effects: The quasi-persistent 27-day variation of intensity.The diurnal variation of intensity. The sporadic emission of very energetic (up to ≈GeV) protons by solar flares. Worldwide impulsive decreases (Forbush decreases) in intensity followed by gradual recovery. The 11-year cycle of intensity and its anticorrelation with the solar activity cycle as measured by sunspot numbers. The 22-year cycle in the amplitude of the diurnal variations.

Editor's Foreword  vii

Acknowledgments  x

Scott E. Forbush, 1904-1984  xi
(A Tribute by Martin A. Pomerantz)
Eos, Q.Q.m, 473-475, 1984

Lectures by Scott E. Forbush entitled "Geomagnetism, Cosmic Radiation, and Statistical Procedures for Geophysicists"

Author's Preface to Lectures  1

I. Earth's Main Field and Its Secular Variation  2

1.1 Introduction 2

1.2 Potential and Field Strength 2

1.3 Gradient 2

1.4 Air-Earth Currents  4

1.5 Magnetic Dipole  4

1.6 Dipole Approximation to Earth's Field 7

1.7 Divergence and Laplace's Equation 10

1.8 Separation ofInternal and External Potential for the Earth's Field  12

1.9 Secular Variations  13

1.10 Drift of the Eccentric Dipole 14

References  19

II. Transient Geomagnetic Variations 20

2.1 Diurnal Variation 20

2.2 Electromagnetic Induction in the Earth  23

2.3 The External Part of the Sq Field 24

2.4 The Lunar Diurnal Variation 28

2.5 Theory for Solar and Lunar Diurnal Variations  30

2.6 Solar Flare Effects 35

2.7 Storm Time Variations 38

2.8 Disturbance Daily Variations  41

2.9 References  43

III. Solar Activity and Geomagnetic Effects 44

3.1 Twenty-Seven Day Recurrences in Magnetic Activity 44

3.2 Solar Cycle and Annual Variation of Magnetic Disturbance and the U-Measure of Activity 49

3.3 Variability of Wave Radiation from the Sun 57

3.4 New Measure for Storm Time Variation 59

References 59

IV. Random Fluctuations, Persistence, and Quasi-Persistence in Geophysical and Cosmical Periodicities 60

4.1 Introduction 60

4.2 General Procedure  60

4.3 Harmonic Analysis . 61

4.4 The Harmonic Dial 2

4.5 Twenty-Seven Day Waves in International

Character Figure C 64

4.6 Standard Deviations for Sine Waves and Residuals 66

4.7 Statistical Procedures for Testing Periodicities  67

4.8 Examples  74

4.9 Periodogram 76

4.10 Quasi-Persistence and Effective Expectancy 79

References 82

V. Time Variations of Cosmic-Ray Intensity 83

5.1 Introduction 83

5.2 Variation of Cosmic-Ray Intensity with Latitude 84

5.3 Magnetic Storm Effects  86

5.4 Twenty-Seven Day Variation 91

5.5 Variations with Solar Cycle 92

References 99

VI. Cosmic-Ray Variations (Continued) and Some IGY Results  99

6.1 Cosmic-Ray Equator and Intensity  99

6.2 Variations Around It  101

6.3 Solar Flare Effects  106

6.4 Alpha Particle Effects X Rays from Aurorae  109

6.5 Protons from the Sun  113

References 114