Magnetoseismology E-Book

Frederick W. Menk

• Herausgeber: Wiley-VCH
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2013

Seitenzahl: 420

Beschreibung

Written by a researcher at the forefront of the field, this first comprehensive account of Magnetoseismology conveys the physics behind these movements and waves, and explains how to detect and investigate them. Along the way, it describes the principles as applied to remote sensing of near-Earth space and related remote sensing techniques, while also comparing and intercalibrating Magnetoseismology with other techniques. The example applications include advanced data analysis techniques that may find wider used in areas ranging from geophysics to medical imaging, and remote sensing using radar systems that are of relevance to defense surveillance systems. As a result, the book not only reviews the status quo, but also anticipates new developments. With many figures and illustrations, some in full color, plus additional computational codes for analysis and evaluation. Aimed at graduate readers, the text assumes knowledge of electromagnetism and physical processes at degree level, but introductory chapters will provide an overview of the relevant plasma physics and magnetospheric physics. The book will thus be of interest to entry-level and established researchers in physics of the Earth's magnetosphere and ionosphere, as well as to students, academics and scientifically literate laypersons with an interest in understanding space weather processes and how these relate to the dynamic behavior of near-Earth space.

Leseprobe

Contents

Cover

Related Titles

Title Page

Copyright

Preface

Color Plates

Chapter 1: Introduction

1.1 Purpose of This Book

1.2 The Solar Wind

1.3 Fluctuations in the Solar Wind

1.4 Early Observations of Geomagnetic Variations

1.5 Properties of Geomagnetic Variations

Chapter 2: The Magnetosphere and Ionosphere

2.1 The Geomagnetic Field

2.2 Structure of Earth's Magnetosphere

2.3 Magnetospheric Current Systems

2.4 The Radiation Belts

2.5 The Inner Magnetosphere

2.6 Formation and Properties of the Ionosphere

2.7 Geomagnetic Disturbances

2.8 Space Weather Effects

Chapter 3: ULF Plasma Waves in the Magnetosphere

3.1 Basic Properties of a Plasma

3.2 Particle Motions

3.3 Low-Frequency Magnetized Plasma Waves

3.4 The Shear Alfvén Mode in a Dipole Magnetic Field

3.5 MHD Wave Mode Coupling in One Dimension

3.6 An Alternative Derivation of the Plasma Wave Equation, from Electromagnetism

Chapter 4: Sources of ULF Waves

4.1 Introduction

4.2 Exogenic Sources

4.3 Boundary Instabilities

4.4 Field Line Resonances

4.5 Cavity and Waveguide Modes

4.6 Spatially Localized Waves

4.7 Ion Cyclotron Waves

Chapter 5: Techniques for Detecting Field Line Resonances

5.1 Introduction

5.2 Variation in Spectral Power with Latitude

5.3 Variation of Phase with Latitude

5.4 Wave Polarization Properties

5.5 Spectral Power Difference and Division

5.6 Single Station H/D

5.7 Cross-Phase from Latitudinally Separated Sensors

5.8 Using ULF Wave Polarization Properties

5.9 Automated Detection Algorithms

Chapter 6: Ground-Based Remote Sensing of the Magnetosphere

6.1 Estimating Plasma Mass Density

6.2 Travel Time Method of Tamao

6.3 Determining Electron Density

6.4 Verification of Ground-Based Mass Density Measurements

6.5 Determining Ion Concentrations

6.6 Field-Aligned Plasma Density

6.7 Plasma Density at Low Latitudes

6.8 Plasma Density at High Latitudes

Chapter 7: Space Weather Applications

7.1 Magnetospheric Structure and Density

7.2 Plasmapause Dynamics

7.3 Density Notches, Plumes, and Related Features

7.4 Refilling of the Plasmasphere

7.5 Longitudinal Variation in Density

7.6 Solar Cycle Variations in Density

7.7 Determining the Open/Closed Field Line Boundary

7.8 Determining the Magnetospheric Topology at High Latitudes

7.9 Wave–Particle Interactions

7.10 Radial Motions of Flux Tubes

Chapter 8: ULF Waves in the Ionosphere

8.1 Introduction

8.2 Electrostatic and Inductive Ionospheres

8.3 ULF Wave Solution for a Thin Sheet Ionosphere

8.4 ULF Wave Solution for a Realistic Ionosphere

8.5 FLRs and the Ionosphere

8.6 Remote Sensing ULF Electric Fields in Space

8.7 Quarter-Wave Modes

8.8 Detection of ULF Waves in the Ionosphere

8.9 Consequences for Radio Astronomy

Chapter 9: Magnetoseismology at Other Planets and Stars

9.1 Magnetoseismology at Other Planets

9.2 Magnetoseismology of the Solar Corona

9.3 Introduction to Helioseismology and Asteroseismology

9.4 Field Line Resonances at Other Stars

Appendix A: Computer Codes

Appendix B: The Transverse MHD Wave Equation for General Magnetic Field Models

References

Index

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© 2013 Wiley-VCH Verlag & Co. KGaA, Boschstr. 12, 69469 Weinheim, Germany

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Print ISBN: 978-3-527-41027-9

ePDF ISBN: 978-3-527-65208-2

ePub ISBN: 978-3-527-65207-5

mobi ISBN: 978-3-527-65206-8

oBook ISBN: 978-3-527-65205-1

Typesetting Thomson Digital, Noida, India

Cover Design Matthew Waters

Preface

One of the joys as a student was building and using relatively simple equipment – magnetometers and ionospheric sounders – to probe the region of space around Earth and gain insight into processes there. This is the essence of this book: remote sensing, mostly using ground-based instruments and techniques, to understand our space environment, the magnetosphere. This region dynamically links interplanetary space with Earth's atmosphere, and is where satellites orbit.

The agents involved are ultralow-frequency plasma waves, since they propagate from the solar wind through the magnetosphere and atmosphere to the ground. These waves transfer energy and momentum and are not only involved in many types of instabilities and interactions but can also be used as a diagnostic monitor of these processes. This book focuses on the second aspect through understanding of the first.

With the move to online data access, undergraduate students can conduct original research using observations from ground arrays, radar networks, and satellites. The magnetosphere is there for everyone to explore. This in turn provides wonderful insight into all the relevant physics, from the cycles of the Sun to the nature of the geomagnetic field and the atmosphere, and exploring other planets.

This book focuses on the underlying principles and their interconnectedness. We do not assume familiarity with physics or mathematics concepts beyond undergraduate level.

Many people have guided our personal journeys. Our scientific mentors include Brian Fraser, John Samson, Keith Cole, and Valerie Troitskaya. Other colleagues include Sean Ables, Brian Anderson, Mark Clilverd, Bob Lysak, Ian Mann, Pasha Ponomarenko, Murray Sciffer, Peter Sutcliffe, and Tim Yeoman. Many students taught us at least as much as we taught them. The development of this monograph was patiently and enthusiastically guided by our editors at Wiley, Nina Stadthaus and Christoph Friedenburg. Of course, this book would not have been possible without the continual support of our families and wives, who suffered in silence a great many evenings while we disappeared into offices to pursue our arcane endeavors.

Newcastle, July 2012

Frederick W. MenkColin L. Waters

Color Plates

Figure 1.1 Comet Hale–Bopp, showing a white dust tail and a blue ion tail, resulting from the effect of the solar wind and entrained magnetic field. Source: Alessandro Dimai and Davide Ghirardo (Associazione Astronomica Cortina) at Passo Giau (2230 m), Cortina d'Amprezzo, Italy, March 16, 1997, 03:42 UT. e-mail: [email protected], web: www.cortinastelle.it - www.skyontheweb.org. (This figure also appears on page 2.)

Figure 2.3 Mercator projection of the total intensity F of the main geomagnetic field computed using the 2010 World Magnetic Model. Contour interval is 1000 nT. From Maus et al. (2010). (This figure also appears on page 17.)

Figure 2.5 Variation in (a) strength and (b) location of the minimum in the total field intensity F in the South Atlantic Anomaly region during the past century. From Finlay et al. (2010). (This figure also appears on page 18.)

Figure 2.9 Yearly averaged 2–6 MeV electron flux measured at low altitudes by the SAMPEX spacecraft during 1993–2001, showing location and intensity of the radiation belts. Data courtesy of Shri Kanekal and SAMPEX Data Center staff. (This figure also appears on page 28.)

Figure 3.1 Charged particle motions in the magnetosphere, showing gyration around a field line, bouncing between mirror points, and azimuthal drift along L shells. Pitch angle is θ. (This figure also appears on page 47.)

Figure 4.3 Schematic representation of the magnetopause, bow shock, and the ion foreshock region (shaded) where ULF waves are likely generated. The IMF is shown northward, and thick arrows represent plasma streamlines. Field lines (solid) map around the magnetopause and the plasma convects antisunward. (This figure also appears on page 66.)

Figure 5.9 Dynamic cross-phase spectra data recorded on February 9, 1995 by the Churchill line of magnetometers of the Canadian array. Time axis is from 0800 to 0530 UT and local noon is at 1800 UT. Cross-phase scale is from 0° to 120°. (This figure also appears on page 99.)

Figure 5.10 The “ellipticity” spectra computed from the north–south component magnetic field data from pairs of latitudinal spaced stations of the Canadian Churchill line. The processing used the same time series as Figure 5.9. (This figure also appears on page 102.)

Figure 5.11 The automatic FLR detection algorithm in Berube, Moldwin, and Weygand (2003) applied to the cross-phase data in Figure 5.9. (This figure also appears on page 104.)

Figure 5.12 The automatic FLR detection algorithm in Berube, Moldwin, and Weygand (2003) applied to the ellipticity data in Figure 5.10. (This figure also appears on page 105.)

Figure 6.1 Logarithm of magnetosphere plasma mass density in units of H+ cm−3 as a function of radial distance and MLT, derived from FLRs detected with the CANOPUS magnetometer array on February 9, 1995. From Waters et al., (2006). (This figure also appears on page 109.)

Figure 6.14 Normalized, mean trace spectral power over 0.1–9 mHz from magnetometer data recorded at Davis, Antarctica. The data are for the full year 1996 and local magnetic noon is near 0940 UT. (This figure also appears on page 129.)

Figure 6.16 Extent in latitude of field line tension and torsion that affects FLR frequencies. (a) Estimates using the Tsyganenko 1996 model. (b) Normalized trace spectra of the horizontal components of magnetometer data from various stations in the Scandinavian IMAGE magnetometer array for the year 1996. (This figure also appears on page 131.)

Figure 7.2 Plasma mass density map for October 16–18, 1990, based on observations from two magnetometer arrays separated by 10 h in local time. Adapted from Menk et al. (1999). (This figure also appears on page 135.)

Figure 7.7 Whole-day L = 2.67 cross-phase frequency–time spectra for (a) September 30, 2002 and (b) October 5, 2002 when a density biteout occurred. (This figure also appears on page 140.)

Figure 7.10 Dynamic cross-phase spectra for May 14, 2001, showing cross-phase polarity reversals, arrowed, at 0730 and 1200–1230 UT. From Kale et al. (2007). (This figure also appears on page 143.)

Figure 7.11 Dynamic cross-phase spectra for station pairs centered on L = 3.9 and L = 3.2 on June 11, 2001, a day after a Kp = 6 storm. A cross-phase reversal with time appears in the upper plot, and a reversal with frequency in the lower plot. (This figure also appears on page 144.)

Figure 7.13 (a) Equatorial electron density (solid line) and resultant resonant frequency profiles for 19–20 UT on June 11, 2001 from a 2.5D numerical model. (b) Corresponding predicted power spectral density for the north–south ground-level magnetic perturbation. (c) Predicted ground cross-phase profile for an interstation spacing of 2°. (This figure also appears on page 145.)

Figure 7.21 Doppler velocity oscillations in beam 5 of the Finland (Hankasalmi) HF radar from 0400–0800 UT on January 6, 1998. (This figure also appears on page 156.)

Figure 8.4 (a) The polarization azimuth computed from ULF bx and by for a frequency of 16 mHz and dip angle of I = 70° at solar maximum ionosphere conditions. The wave numbers are kx = 10−10 m−1 and ky varying between 10−8 and 10−4 m−1. (b) The amplitude of the field-aligned (compressional) component of the ULF wave magnetic field for the parameters used in panel (a). From Sciffer, Waters, and Menk (2005). (This figure also appears on page 175.)

Figure 8.16 The variation in differential phase for a 70 MHz signal due to changes in TEC from a 15 mHz ULF wave with ULF wave mix of 80% shear Alfvén mode at 1000 km altitude, as a function of the ULF wave spatial scale size. Conditions were for local noon using the divergence term (last term in Equation 8.42) only. From Waters and Cox (2009). (This figure also appears on page 193.)

1

Introduction

1.1 Purpose of This Book

This book describes how measurements of naturally occurring variations of Earth's magnetic field can be used to provide information on the near-Earth space environment. This is a complex and highly dynamic region, the home of space weather that affects orbiting spacecraft and technological systems on the ground. The measurements come mostly from ground-based magnetometers but also from high-frequency radars, very low-frequency radio propagation circuits, and satellite platforms. Such remote sensing is possible because magnetic field lines originating in Earth extend through the atmosphere into space and respond to perturbations in the solar wind, which are transmitted earthward by periodic magnetic and electric field perturbations called plasma waves.

This area of research is called magnetoseismology. Its study and use for remote sensing require knowledge of and provide information on the solar wind, the interface between the solar wind and Earth's (geo)magnetic field, the near-Earth plasma environment and its variable particle populations, the ionized region of the atmosphere, and to some extent the subsurface structure of the ground.

The book does not assume familiarity with concepts in space physics and plasma physics. However, there is a strong emphasis on understanding of the core concepts and the consequent science applications. This is a new and exciting field, which greatly extends the utility of ground and in situ observations and mathematical descriptions of the observed phenomena.

1.2 The Solar Wind

Our planet Earth is immersed in the Sun's outer atmosphere. Particles streaming outward from the Sun exert pressure upon interplanetary matter, evident from observations of comet tails. As seen in Figure 1.1, comets may form two tails: a dust tail arising from the combined effects of radiation pressure on the low-mass dust particles and inertia of the heavier grains, and an ion tail due to the pressure exerted on gas in the comet's coma by the streaming solar particles and an embedded magnetic field. Biermann (1951) thus deduced that particles flow continuously outward from the Sun with velocities of order 103 km s−1. Parker (1959) called this stream the solar wind and showed that it arises from the supersonic expansion of the solar corona into space along magnetic lines of force originating in the Sun and due to the pressure gradient between the coronal gas (~10−3 Pa) and interplanetary space (~10 Pa). Further details appear in a number of reviews (e.g. Aschwanden, 2005; Goldstein , 2005; Hundhausen, 1995; Watermann , 2009). The solar wind energy flux reaching Earth's magnetosphere boundary is around 10 W, imparting a force of order 4 × 10 N.