Ring Current Investigations: The Quest for Space Weather Prediction [1 ed.] 012815571X, 9780128155714

Table of contents :
Cover
Ring Current
Investigations:
The Quest for Space
Weather Prediction
Copyright
Contributors
Preface
Chapter 1 - Introduction and historical background
1.1 - Historical overview
1.2 - Relation to solar wind drivers
1.3 - Space weather effects
1.4 - Book content
Acknowledgments
References
Chapter 2 - Observations and measurement techniques
2.1 - Early ring-current measurements
2.1.1 - Ring current energy density
2.1.2 - Ring current ion spectra
2.2 - Ring current composition and the source of the ring current
2.2.1 - Low-energy measurements
2.2.2 - The “bulk” of the ring current
2.2.2.1 - Storm-time energy density
2.2.2.2 - The role of the solar wind source
2.2.2.3 - Signatures of transport/loss in Ion spectra
2.2.2.4 - Statistical models, including quiet time observations
2.3 - Imaging the ring current
2.4 - Multispacecraft measurements and recent results
2.4.1 - The Cluster mission
2.4.2 - Van Allen Probes and Arase
2.4.2.1 - Ring current development
2.4.2.2 - Low L-shell heavy ion features
2.4.2.3 - Statistical studies of the ring current
2.5 - Summary
References
Chapter 3 -Theoretical description
3.1 - Motivation
3.2 - Single particle motion in electromagnetic fields
3.2.1 - Maxwell’s equations
3.2.2 - The Lorentz force
3.2.3 - Particle motion in a uniform magnetic field
3.2.4 - Particle motion in nonuniform magnetic field
3.2.5 - Magnetic mirroring
3.2.6 - Gradient-curvature drift
3.3 - Adiabatic invariants
3.4 - Statistical description: elements of kinetic theory
3.4.1 - The Boltzmann equation
3.4.2 - Macroscopic variables as moments of the distribution function
3.5 - Motion in a nonuniform magnetic field
3.6 - Bounce averaged drifts
3.6.1 - Bounce-averaged particle drifts
3.6.2 - Bounce-averaged drifts in arbitrary magnetic fields
3.6.3 - Magnetospheric electric field
3.7 - Losses
3.7.1 - Charge exchange
3.7.2 - The role of charge exchange in the loss of ring current ions
3.7.3 - Coulomb collisions
3.7.4 - Scattering via wave particle interactions
3.7.4.1 - Minimum resonant energy
3.7.5 - Wave properties in hot plasma
3.7.5.1 - Quasi-linear diffusion coefficients
3.7.6 - Convective loss
3.8 - Conclusions
Appendix A. Equatorial gyro-frequency
Appendix B. Equatorial gyro-radius
Appendix C. Bounce period
References
Chapter 4 - Modeling techniques
Abstract
Keywords
4.1 - Introduction
4.2 - Empirical models
4.2.1 - Low-dimensional models
4.2.2 - Ion and electron flux models
4.2.3 - Electric field models
4.2.4 - Magnetic field models
4.2.4.1 - The internal magnetic field
4.2.4.2 - Modeling the external magnetic field
4.3 - Theoretical models
4.3.1 - Introduction
4.3.2 - The Rice Convection Model
4.3.3 - The MSM and MSFM
4.3.4 - The RCM-Equilibrium (RCM-E)
4.3.5 - RCM-Jupiter/Saturn
4.3.6 - Fontaine, Senior, Blanc, and Peymirat convection model
4.3.7 - The Chen ring current model
4.3.8 - The Fok ring current and the comprehensive ring current model (CRCM) models
4.3.9 - The ring current-atmosphere interactions model (RAM)
4.3.10 - The ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB)
4.3.11 - HEIDI
4.3.12 - GEMSIS
4.3.13 - Coupled global MHD models
4.3.14 - Data assimilation models
4.3.15 - Particle tracing algorithms
4.4 - Discussion and summary
Acknowledgments
References
Chapter 5 - Ring current development
5.1 - Introduction
5.2 - Ring current sources
5.2.1 - Plasma sheet
5.2.2 - Direct ionosphere to ring current plasma transfer?
5.3 - Ring current particle transport: convective and diffusive
5.4 - Effect of plasma sheet variations on ring current intensity
5.5 - Effects of magnetic self-consistency
5.6 - Model-data comparisons of ring current development
5.7 - Challenges for future understanding of ring current development
Acknowledgments
References
Chapter 6 - Ring current decay
6.1 - Introduction
6.2 - Charge exchange
6.3 - Coulomb collisions
6.4 - Precipitation losses
6.4.1 - Observations of particle precipitation
6.4.2 - Wave-particle interactions
6.4.3 - Field line curvature scattering
6.4.4 - Other mechanisms
6.5 - Magnetopause losses
6.6 - Discussion and conclusions
Acknowledgments
References
Chapter 7 - Cross-regional coupling
7.1 - Roles of ring current in magnetosphere-ionosphere coupling
7.2 - Magnetic effects of the ring current
7.3 - Ring current velocity anisotropy and plasma wave growths
7.4 - Electric coupling between the ring current and ionosphere
7.5 - Ring current moderation with the ionospheric conductivity
7.6 - Final remark
Acknowledgment
References
Chapter 8 - Space weather effects and prediction
8.1 - Effects of space weather
8.2 - Spacecraft charging and electrostatic discharges
8.2.1 - Surface charging
8.2.2 - Worst-case charging environments and spacecraft design
8.2.3 - Frame charging and differential charging
8.2.4 - Internal charging
8.2.5 - Internal charging models
8.2.6 - Space environment models and charging analyses
8.3 - Geomagnetically induced currents
8.4 - Conclusions
Acknowledgments
References
Chapter 9 - Comparative planetary ring currents
9.1 - Comparing planetary magnetospheres
9.1.1 - Solar wind versus rotation
9.1.2 - Neutral materials
9.1.2.1 - Satellites
9.1.2.2 - Gas, dust, and plasmas from satellites
9.1.2.3 - Calculating losses from passive satellites
9.2 - How does a rotationally driven magnetosphere operate?
9.3 - Comparing ring current populations
9.3.1 - Kennel-Petschek theory
9.3.2 - Limiting spectra at the target planets
9.4 - Ring current population dynamics and sources
9.5 - Ring current population losses
9.6 - Uranus (and Neptune)
9.7 - Discussion
9.8 - Appendix
References
APPENDIX
1 Frequently Used Abbreviations
APPENDIX
2 Useful Websites and Download Links
APPENDIX
3 Illustrative Movies and Other Materials
Index
Back Cover

Citation preview

Ring Current Investigations The Quest for Space Weather Prediction Edited by

Vania K. Jordanova Raluca Ilie Margaret W. Chen

Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright © 2020 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www. elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-12-815571-4 For information on all Elsevier publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Candice Janco Acquisitions Editor: Marisa LaFleur Editorial Project Manager: Sara Valentino Production Project Manager: Joy Christel Neumarin Designer: Christian J. Bilbow Typeset by Thomson Digital

Contributors Margaret W. Chen The Aerospace Corporation, Space Sciences Application Laboratory, Los Angeles, CA, United States Mei-Ching Fok Geospace Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, United States Raluca Ilie University of Illinois at Urbana-Champaign, Champaign, IL, United States Vania K. Jordanova Los Alamos National Laboratory, Space Science and Applications, Los Alamos, NM, United States Lynn M. Kistler University of New Hampshire, Space Science Center and Physics Department, Durham, NH, United States; Nagoya University, Institute for Space Earth Environmental Research, Nagoya, Aichi, Japan Barry H. Mauk The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States James L. Roeder The Aerospace Corporation, Los Angeles, CA, United States Frank Toffoletto Rice University, Physics and Astronomy Department, Houston, TX, United States

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Preface The inner regions of the Earth’s space environment, or the inner magnetosphere, are composed of several distinct plasma populations that could be differentiated by their specific temperature or density (e.g., plasmasphere, ring current, radiation belts, and plasma sheet). These inner magnetospheric plasma populations interact with each other and with the outer magnetosphere and ionosphere through a variety of physical processes leading to particle injections, acceleration, and loss. Abrupt changes of several orders of magnitude can occur in the particle distributions, and the most dramatic variations, related to the development of large geomagnetic storms, are linked to harmful space weather effects. As society becomes more and more dependent on sophisticated technologies operating both in space and on the ground, the need to provide a timely and reliable forecast of the space environment increases. Despite years of ground-based, global imaging, and in situ satellite observations, as well as numerical modeling studies, accurate “space weather” forecasts remain a big challenge, due to the complexity of the highly dynamic near-Earth region. This book is motivated by the growing interest in space weather prediction. It provides in-depth coverage of the dynamics of energetic particles forming the ring current populations, the main signature of a geomagnetic storm, using observations, theory, and numerical modeling. The development of the Earth’s ring current depends strongly on the plasma sheet source population and the magnitude of electromagnetic fields, which control particles’ injection, depth of penetration, and trapping. Its decay is dictated by losses due to collisions with neutral and charged particles, wave-particle interactions, flow out to the dayside magnetopause, and particle precipitation into the atmosphere. With ring current observations at other strongly magnetized planets of the solar system, such as Jupiter, Saturn, Uranus, and Neptune, similarities and differences to the ring current system at Earth have been discovered. This book provides a comprehensive review of important advances in ring current research from recent publications and stimulating discussions at the International Space Science Institute in Bern, Switzerland, the American Geophysical Union Fall Meetings, and the National Science Foundation/Geospace Environment Modeling Workshops. It contains nine highly coordinated chapters that have been independently refereed, and an Appendix with useful links to illustrative video clips, public data, and opensource code downloads. The book material also reviews relevant concepts in basic plasma physics theory, electromagnetism, and kinetic theory, in the context of ring current development and decay. The book is intended to serve as

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Preface

a comprehensive reference to researchers, professors and students interested in understanding the underlying physical mechanisms of geomagnetic storms and in simulating their effects. Vania K. Jordanova Los Alamos National Laboratory, Los Alamos, NM Raluca Ilie University of Illinois at Urbana-Champaign, Urbana, IL Margaret W. Chen The Aerospace Corporation, Los Angeles, CA

CHAPTER

Introduction and historical background

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Vania K. Jordanovaa, Raluca Ilieb, Margaret W. Chenc a

Los Alamos National Laboratory, Space Science and Applications, Los Alamos, NM, United States; b University of Illinois at Urbana-Champaign, Champaign, IL, United States; cThe Aerospace Corporation, Space Sciences Application Laboratory, Los Angeles, CA, United States

1.1  Historical overview The defining characteristic feature of a geomagnetic storm that is observed in the magnetograms of near-equatorial ground-based stations is the decrease of the horizontal component of the Earth’s magnetic field and its subsequent recovery. Hourly values of the average global variation of this component, measured at low-latitude observatories (Fig. 1.1A), are used to specify the intensity of the geomagnetic storm and are referred to as the Dst index (Sugiura, 1964). This index has been compiled by the World Data Center for Geomagnetism in Kyoto, Japan, since 1964. Usually, the largest magnetic storms are preceded by a sudden impulse called storm sudden commencement (SSC), signaling the arrival of an interplanetary shock structure. The main phase of the geomagnetic storm is associated with the enhancement of the ring current due to particle energization and trapping, while the recovery phase is associated with its decay due to various loss processes. Another index available since 1932 from the Institute of Geophysics in Gottingen, and later from the GFZ Helmholtz Centre in Potsdam, Germany, and used to classify the geomagnetic activity on a global scale is the Kp index, a number between 0 and 9 indicating the level of disturbance in a given 3-hour interval of the universal day. A detailed description of various geomagnetic indices and their use is given by Mayaud (1980). Time variations in the Earth’s magnetic field were reported for the first time around 1635, in a book entitled “A discourse mathematical on the variation of the magneticall needle: Together with its admirable diminution lately discovered” by Henry Gellibrand, professor of Astronomy at the Gresham College (Gellibrand, 1635). However, it was not until 1847, when Carl Friedrich Gauss, together with Wilhelm Weber, established the first magnetic observatory in Gottingen, Germany, and measurements of the terrestrial magnetic field in various regions of the Earth were made possible. Gauss’ method of measuring the horizontal component of the terrestrial magnetic field has provided the mathematical foundation in assessing the geomagnetic disturbances on the ground. Ground disturbances were reported to have various periodicities: from diurnal, first discovered in London in 1722 by George Graham Ring Current Investigations. http://dx.doi.org/10.1016/B978-0-12-815571-4.00001-9 Copyright © 2020 Elsevier Inc. All rights reserved.

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CHAPTER 1  Introduction and historical background

FIGURE 1.1 (A) Hourly Dst values during the geomagnetic storm of July 9 1966 based on groundbased data from Honolulu, Tucson, San Juan, Guam and Surlari magnetometers. (B) Directional intensities of protons with energies between 31 and 49 keV as a function of radial distance, during the July 9, 1966 geomagnetic storm. Source: From Frank (1967).

(a clockmaker also interested in astronomy and geomagnetism), to secular; however, some irregular disturbances were also reported and remained unexplained until 1912, when Carl Stormer interpreted them as a consequence of the formation of a donutshape equatorial ring of electrons, moving on closed field lines in a region between 30,000 and 10,000,000 km (Stormer, 1912). This is the first time the existence of a “ring current” is hypothesized. It was not until 1967, when ring current particles were first detected by instruments onboard the OGO 3 spacecraft (Frank, 1967); Fig. 1.1B shows the first measurements of ring current proton fluxes during the geomagnetic storm of July 9, 1966. Numerous studies followed, that focused on the detection and estimation of ring current characteristic properties (Hoffman and Cahill, 1968; Konradi et al., 1973; Longanecker and Hoffman, 1973; Cahill, 1973; Williams and Lyons, 1974; Berko et al., 1975). In 1951, observations of precipitating energetic neutral hydrogen into the upper atmosphere during auroral substorms were linked to the existence of energetic neutral atoms (ENAs) by Meinel (1951), and were discovered to contribute to the ring current decay (Fite et al., 1958; Dessler and Parker, 1959; Stuart, 1959) by means of charge exchange between protons and neutral atmospheric hydrogen atoms. These discoveries led to the first global image of the ring current, based on measurements of actual energetic neutral atom fluxes (Roelof, 1987) from the ISEE-1 spacecraft. Besides the ring current, which is of major interest to this book, other magnetospheric current systems are the tail, field-aligned, and magnetopause currents

1.2 Relation to solar wind drivers

FIGURE 1.2 Schematic illustration of Earth’s magnetosphere, showing the major distinct regions and electric current systems. Source: From Pollock et al. (2003).

(Fig. 1.2). The relative contribution of each of these currents to Dst is not well established and was estimated by different authors as being minor (Burton et al., 1975; O’Brien and McPherron, 2000; Turner et al., 2000), major (Alexeev et al., 1996), or storm-dependent (e.g., Ganushkina et al., 2004).

1.2  Relation to solar wind drivers Satellite observations have shown that our planet Earth is immersed into the continuous flow of plasma from the Sun called the solar wind, traveling on average at about 400 km/s, with a particle density of ∼10 cm–3, and carrying a magnetic field of about 5 nT. The bulk of this flow is diverted around the planet by the strong intrinsic magnetic field of the Earth, forming a tear-drop shaped magnetic cavity known as the magnetosphere (Fig. 1.2). This cavity is populated by thermal plasma and energetic charged particles whose motion is governed by the surrounding electric and magnetic fields. At near-Earth distances, low-energy (electronvolt, eV) plasma corotates with the Earth and forms the plasmasphere (Carpenter and Anderson, 1992), populated by outflow from the ionosphere. Particles at relativistic (MeV) energies

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CHAPTER 1  Introduction and historical background

FIGURE 1.3 Adiabatic flow pattern (solid arrows) of magnetospheric protons (E ∼10 − 200 keV) in the equatorial plane. Dashed curves represent boundaries of plasma sheet and plasmasphere. Source: From Schulz and Lanzerotti (1974).

get trapped on closed geomagnetic field lines thereby forming the radiation belts, whose source is still the subject of intensive research (Mauk et al., 2013). The intermediate-energy (keV) charged particles that are injected from the plasma sheet, and for which the electric and magnetic drifts are of comparable importance, form the ring current (Fig. 1.3). The strength of the ring current is commonly used as a measure of geomagnetic storm intensity through the Dst index. The ring current is centered at the magnetic equatorial plane, with an outer boundary located where the magnetic field is no longer able to maintain closed particle orbits around the Earth (stable trapping), and an inner boundary determined by the dense atmosphere. For typical ring current energies from ∼1 keV to 300 keV, the inner magnetosphere region under consideration thus extends between ∼2 and 8 Earth radii (RE) (Schulz and Lanzerotti, 1974). Gonzalez et al. (1994) suggested a definition of a geomagnetic storm as “an interval of time when a sufficiently intense and long-lasting interplanetary convection electric field leads, through a substantial energization in the magnetosphereionosphere system, to an intensified ring current strong enough to exceed some key threshold of the quantifying storm time Dst index”. Furthermore, from all observed Dst values during 1976–1986, approximately 1% were more negative than −100 nT and were classified as great (intense) storms, approximately 7% were between −50 nT and −100 nT and were classified as moderate storms, and Dst values between −30 nT and −50 nT, which occurred less than 20% of the time, were classified as

1.2 Relation to solar wind drivers

FIGURE 1.4 Schematic of the solar-interplanetary-magnetosphere coupling during solar maximum years, during which a coronal mass ejection is the most important solar source for interplanetary and magnetospheric disturbances. Source: From Gonzalez et al. (1994).

weak storms. The main process coupling the solar wind momentum and energy to the magnetosphere and driving magnetospheric energization and geomagnetic storms is thought to be reconnection of the interplanetary and Earth’s magnetic fields at the low-latitude dayside magnetopause (Dungey, 1961) as shown in Fig. 1.4. The passage at Earth of solar wind plasma carrying a strong and persistent southward-oriented interplanetary magnetic field (IMF) causes an intensification of the large-scale electric field across the magnetotail (Fig. 1.2). As a result, the earthward flow of ions and electrons inside the magnetosphere increases, the ring current grows significantly, and the Dst index decreases rapidly; a geomagnetic storm occurs. Kamide et al. (1998) thus found that for more than 50% of intense geomagnetic storms, the main phase undergoes a two-step growth in the ring current that could be associated with the arrival of double-structured southward IMF at the magnetosphere. During intense geomagnetic storms the efficiency of energy transfer through large-scale magnetopause reconnection was estimated on the basis of various coupling functions to ∼10% (Gonzalez et al., 1989). Wave motions produced by viscous interaction between the solar wind plasma and the magnetospheric plasma (Axford and Hines, 1961) seemed to have a minor contribution, and were estimated to be ∼1% efficient during intense northward IMF (Tsurutani et al., 1992). Because of the variety of phenomena occurring on the Sun, solar wind conditions are not constant but may change abruptly with time, and so does the energy input

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CHAPTER 1  Introduction and historical background

to the magnetosphere. Most important is the 11 year solar cycle which results from the periodic reversal of that part of the Sun’s internal magnetic field that impacts the interplanetary environment, with “solar maximum” and “solar minimum” phases greatly influencing the conditions within Earth’s magnetosphere. The overall geomagnetic activity also has a seasonal variability with maxima at the equinoxes (Russell and McPherron, 1973), and tends to become enhanced during the descending phase of the solar cycle, near solar minimum (Legrand and Simon, 1991). Intense storms (peak Dst