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Lecture Notes in Physics

Volume 932

Founding Editors W. Beiglbo¨ck J. Ehlers K. Hepp H. Weidenmüller Editorial Board M. Bartelmann, Heidelberg, Germany B.-G. Englert, Singapore, Singapore P. Ha¨nggi, Augsburg, Germany M. Hjorth-Jensen, Oslo, Norway R.A.L. Jones, Sheffield, UK M. Lewenstein, Barcelona, Spain H. von Lo¨hneysen, Karlsruhe, Germany J.-M. Raimond, Paris, France A. Rubio, Hamburg, Germany M. Salmhofer, Heidelberg, Germany W. Schleich, Ulm, Germany S. Theisen, Potsdam, Germany D. Vollhardt, Augsburg, Germany J.D. Wells, Ann Arbor, USA G.P. Zank, Huntsville, USA

The Lecture Notes in Physics The series Lecture Notes in Physics (LNP), founded in 1969, reports new developments in physics research and teaching-quickly and informally, but with a high quality and the explicit aim to summarize and communicate current knowledge in an accessible way. Books published in this series are conceived as bridging material between advanced graduate textbooks and the forefront of research and to serve three purposes: • to be a compact and modern up-to-date source of reference on a well-defined topic • to serve as an accessible introduction to the field to postgraduate students and nonspecialist researchers from related areas • to be a source of advanced teaching material for specialized seminars, courses and schools Both monographs and multi-author volumes will be considered for publication. Edited volumes should, however, consist of a very limited number of contributions only. Proceedings will not be considered for LNP. Volumes published in LNP are disseminated both in print and in electronic formats, the electronic archive being available at springerlink.com. The series content is indexed, abstracted and referenced by many abstracting and information services, bibliographic networks, subscription agencies, library networks, and consortia. Proposals should be sent to a member of the Editorial Board, or directly to the managing editor at Springer: Christian Caron Springer Heidelberg Physics Editorial Department I Tiergartenstrasse 17 69121 Heidelberg/Germany [email protected]

More information about this series at http://www.springer.com/series/5304

Donald V. Reames

Solar Energetic Particles A Modern Primer on Understanding Sources, Acceleration and Propagation

Donald V. Reames Institute for Physical Science and Technology University of Maryland College Park, MD USA

ISSN 0075-8450 ISSN 1616-6361 (electronic) Lecture Notes in Physics ISBN 978-3-319-50870-2 ISBN 978-3-319-50871-9 (eBook) DOI 10.1007/978-3-319-50871-9 Library of Congress Control Number: 2017935369 © Springer International Publishing AG 2017 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

It is common for scientific texts to be organized in logical rather than historical order. Unfortunately, perhaps, nature does not always proceed in that fashion. In an actively evolving field, new ideas and observations build slowly, step by step, often reversing course, and a student should be prepared for this. Therefore, I have included much of the backing and filling and the individual observations which have led to our present understanding. In reading this book, it is important to keep in mind that a realistic understanding must incorporate different kinds of observations. No single inquiry will suffice. Like reading a murder mystery, it is normal to speculate along the way, but we must eventually consider all the evidence, which is not available early in the story. There are many pieces of evidence, of many different kinds, in this mystery. There is now a wealth of evidence on abundances of chemical elements and isotopes and their ionization states and much on electrons; there is onset timing, radio evidence, and the streaming limit; there are injection profiles, intensity dropouts, energy spectral shapes, spectral knees, and particle reservoirs, in addition to the solar associations. All of these help us find the origin, acceleration, distribution, and transport of the solar energetic particles (affectionately SEPs). This has become a rich field. Unlike the murder mystery, however, our hard-won understanding also raises new questions for future scientists to address. The story of SEPs is actually covered in five chapters. Chapter 1 provides a background and an introduction to SEP properties. Chapters 2 and 3 present the history and much of the physical evidence for the separation of impulsive and gradual SEP events. Chapters 4 and 5 consider properties of each of these classes individually. The later chapters provide supplementary information on high energies and radiation hazards of SEPs (Chap. 6) and on SEP measurements (Chap. 7) and a Summary and Conclusions (Chap. 8). I hope students of SEPs will enjoy reading this book as much as I have enjoyed writing it. College Park, MD

Donald V. Reames v

Acknowledgments

First, I would like to thank those scientists who have contributed their efforts to the progress of this field and those who have contributed the figures I have used to illustrate their discoveries. Special thanks go to Louis Barbier, Daniel Berdichevshy, Ed Cliver, Steve Kahler, Mary Ann Linzmayer, Chee Ng, Ron Turner, and Gary Zank for reading and commenting on this manuscript and for helpful discussions leading to its preparation. I would especially like to thank Chee Ng for his assistance with the theory of particle transport, wave growth, and shock acceleration.

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About the Author

Born and raised in Florida, Don Reames received his education, leading in 1964 to a PhD in Nuclear Physics, at the University of California at Berkeley. He then joined a group at NASA’s Goddard Space Flight Center in Maryland using sounding rockets and balloons to study galactic cosmic rays and energetic particles from the Sun. He subsequently used data from experiments on the Gemini, IMP, ISEE, Helios, Voyager, Wind, and STEREO missions, as well as many related solar missions, to study those particles and their origins more extensively. He retired from NASA in 2003 to assume an Emeritus position but also soon joined the Institute for Physical Science and Technology at the University of Maryland in College Park to become a Senior Research Scientist. His honors include the 2012 George Ellery Hale Prize from the Solar Physics Division of the American Astronomical Society for his work on the composition and transport of solar energetic particles.

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Contents

1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 The Structure of the Sun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 The Solar Magnetic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Coronal Mass Ejections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Interplanetary Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Solar Energetic Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 Time Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.2 Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.3 The Solar Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.4 Relativistic Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 2 3 4 6 7 7 7 10 11 12

2

History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 The First SEPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Solar Radio Bursts and Electrons . . . . . . . . . . . . . . . . . . . . . . . 2.3 The Spatial Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Diffusion and the Birdcage Model . . . . . . . . . . . . . . . . 2.3.2 Large Scale Shock Acceleration and CMEs . . . . . . . . . . 2.3.3 The Longitude Distribution . . . . . . . . . . . . . . . . . . . . . 2.3.4 Scatter-Free Events . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.5 Field-Line Random Walk . . . . . . . . . . . . . . . . . . . . . . . 2.4 Element Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 First Ionization Potential (FIP) and A/Q . . . . . . . . . . . . 2.4.2 3He-Rich Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.3 The Seed Population . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Ionization States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Shock Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Disappearing-Filament Events . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 “The Solar Flare Myth” . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15 15 16 17 17 17 18 18 19 20 21 22 24 27 29 29 30

. . . . . . . . . . . . . . . . .

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2.9 Wave Generation and the Streaming Limit . . . . . . . . . . . . . . . . . 2.10 SEP–CME Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

31 31 33

3

Distinguishing the Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 SEP Onset Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Realistic Shock-SEP Timing and Correlations . . . . . . . . . . . . . 3.3 Injection Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 High-Energy Spectra and Spectral Knees . . . . . . . . . . . . . . . . . 3.5 Intensity Dropouts and Compact Sources . . . . . . . . . . . . . . . . . 3.6 Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 SEPs as Probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . .

39 39 42 44 45 46 47 48 50 52

4

Impulsive SEP Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Selecting Impulsive Events . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Sample Impulsive Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Energy Dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Abundances for Z  26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Abundances for 34  Z  82 . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Power-Law Enhancements in A/Q: Source-Plasma Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Associations: CMEs, Flares, and Jets . . . . . . . . . . . . . . . . . . . . 4.8 Can We Have It Both Ways? . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Nuclear Reactions: Gamma-Ray Lines and Neutrons . . . . . . . . 4.10 Open Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . .

55 56 57 58 59 59

. . . . . .

61 63 67 68 69 70

Gradual SEP Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Parallel Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Diffusive Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Wave Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 Particle Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.4 Initial Abundance Ratios . . . . . . . . . . . . . . . . . . . . . . . . 5.1.5 The Streaming Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.6 Electron Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Angular Distributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Models and Shock Acceleration . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Shock Acceleration In Situ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Abundances and FIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Source-Plasma Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Spatial Distributions and the Reservoir . . . . . . . . . . . . . . . . . . . 5.8 Non-thermal Variations: Impulsive Vs. Gradual SEPs . . . . . . . . . 5.9 Open Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

73 74 74 75 76 77 78 81 81 81 83 87 87 92 95 97 98

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Contents

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6

High Energies and Radiation Effects . . . . . . . . . . . . . . . . . . . . . . . . 6.1 High-Energy Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 The Streaming Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Radial Dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 A Mission to Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 The Upper Atmosphere of Earth . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

103 103 106 108 109 110 110

7

Measurements of SEPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Single-Element Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 ΔE Versus E Telescopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 An Example: LEMT . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Isotope Resolution: SIS . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Time-of-Flight Versus E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 NOAA/GOES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 High-Energy Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Problems and Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

113 114 115 116 118 119 121 121 122 124

8

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

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List of Abbreviations

CME DH DSA EMIC ESA FIP GCR GLE GSFC ICME LSSA NASA NOAA QLT SEP SPR TAC UV

Coronal mass ejection Decametric-hectometric (radio-emission frequencies) Diffusive shock acceleration Electromagnetic ion cyclotron (plasma waves) European Space Agency First ionization potential Galactic cosmic ray Ground-level event, Ground-level enhancement event Goddard Space Flight Center Interplanetary CME Large-scale shock acceleration National Aeronautics and Space Administration National Oceanic and Atmospheric Administration Quasi-linear theory Solar energetic particle Solar particle release (time at the Sun) Time-to-amplitude converter Ultraviolet

Instruments AIA AMS EIT EPS LASCO HEPAD LEMT

Atmospheric Imaging Assembly, on SDO Alpha Magnetic Spectrometer, on International Space Station Extreme-Ultraviolet Imaging Telescope, on SOHO Energetic-Particle Sensor, on GOES Large-Angle and Spectrometric Coronagraph, on SOHO High-Energy Proton and Alpha Detector, on GOES Low-Energy Matrix Telescope, on Wind xv

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SIS SIT STEP ULEIS

List of Abbreviations

Solar Isotope Spectrometer, on ACE Suprathermal Ion Telescope, on STEREO SupraThermal Energetic Particle, on Wind Ultralow-Energy Isotope Spectrometer, on ACE

Spacecraft ACE GOES IMP ISEE PAMELA SDO SOHO STEREO

Advanced Composition Explorer Geostationary Operational Environmental Satellites Interplanetary Monitoring Platform International Sun–Earth Explorer Payload for Antimatter Exploration and Light-nuclei Astrophysics Solar Dynamics Observatory Solar and Heliospheric Observatory Solar Terrestrial Relations Observatory