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The Sun As a Guide to Stellar Physics This Page Intentionally Left Blank the Sun As a Guide to Stellar Physics The Sun as a Guide to Stellar Physics This page intentionally left blank The Sun as a Guide to Stellar Physics Edited by Oddbjørn Engvold Professor emeritus, Rosseland Centre for Solar Physics, Institute of Theoretical Astrophysics, University of Oslo, Oslo, Norway Jean-Claude Vial Emeritus Senior Scientist, Institut d’Astrophysique Spatiale, CNRS-Universite´ Paris-Sud, Orsay, France Andrew Skumanich Emeritus Senior Scientist, High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado, United States 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 © 2019 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: 978-0-12-814334-6 For information on all Elsevier Publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Candice Janco Acquisition Editor: Marisa LaFleur Editorial Project Manager: Tasha Frank Production Project Manager: Nilesh Kumar Shah Designer: Miles Hitchen Typeset by TNQ Technologies (Main image) Anatomy of the Sun - Image of the Sun showing the Corona, Chromosphere and Photosphere, with a cut-away portion showing its interior, i.e. through the Convective and Radiative Zone into the Sun’s Core. Credit: Bernhard Fleck, SOHO/ESA/NASA. (Left) An image of a sunspot group near solar disk center observed with the Swedish 1-m Solar Telescope on 15 July 2002. Credit: Go¨ran B. Scharmer and Mats G. Lo¨fdahl, Institute for Solar Physics, Stockholm University. (Middle) Composite image of the Sun showing a Coronal Mass Ejection heading for Earth’s magnetic field and an artistic view of the Earth’s bullet-shaped magnetosphere. Credit: ESA/NASA/SOHO/LASCO/EIT. (Right) Coronal loops seen above the solar edge with the TRACE (Transition Region and Coronal Explorer) instrument in the light of eight times ionized Iron (Fe 17.1 nm). Credit: Alan Title, Solar Astrophysics Laboratory, Lockheed Martin Advanced Technology Center, Palo Alto, California. Contents List of Contributors................................................................................. xv Preface ............................................................................................... xvii CHAPTER 1 Discoveries and Concepts: The Sun’s Role in Astrophysics ....................................................... 1 Jack B. Zirker and Oddbjørn Engvold 1. The Solar Constant.............................................................. 2 2. The Sun’s Chemical Composition .......................................... 3 2.1 Spectroscopic Methods ...................................................3 2.2 Modeling of the Sun’s Atmosphere...................................4 2.3 Settling of Light Elements...............................................5 3. Internal Structure and Helioseismology................................... 6 3.1 Detection of Oscillatory Pattern........................................6 3.2 Interpretation of Solar Oscillations....................................7 4. The Magnetic Sun and Its Variability...................................... 8 4.1 Solar Cycle...................................................................9 4.2 Magnetic Fields.............................................................9 4.3 Internal Structure and Location of the Magnetic Dynamo ..................................................................... 10 5. The Solar Corona and Wind.................................................11 5.1 The Temperature of the Corona...................................... 11 5.2 The Shape of the Corona............................................... 13 5.3 The Solar Wind........................................................... 13 6. EartheSun Connection........................................................14 6.1 Aurora and Geomagnetic Storms.................................... 14 6.2 The Carrington Event ................................................... 15 6.3 Solar Flares, X-Rays and Energetic Particles .................... 16 6.4 Reconnection of Magnetic Fields.................................... 17 6.5 Coronal Mass Ejections ................................................ 18 7. Testing Two Concepts.........................................................19 7.1 Neutrino Oscillations in the Sun..................................... 19 7.2 Testing General Relativity............................................. 22 8. Concluding Remarks...........................................................23 Acknowledgments ..................................................................24 References.............................................................................24 v vi Contents CHAPTER 2 Stellar and Solar Chromospheres and Attendant Phenomena............................................................27 Thomas R. Ayres 1. Introduction ......................................................................27 2. Why Chromospheres Exist...................................................28 2.1 Stellar Convection Zones .............................................. 28 2.2 The Solar Chromosphere............................................... 29 2.3 Stellar Chromospheres.................................................. 31 2.4 Why Are Chromospheres So Thick? ............................... 32 2.5 The WilsoneBappu Effect............................................. 43 3. The RotationeAgeeActivity Connection ...............................45 3.1 Background ................................................................ 45 3.2 PosteSkumanich Law Insights Into the Rotatione AgeeActivity Connection ............................................. 46 3.3 Theory Behind the Skumanich Law ................................ 50 4. Stellar Activity Cycles ........................................................52 References.............................................................................56 CHAPTER 3 The Sun’s Atmosphere............................................59 Alexander I. Shapiro, Hardi Peter, and Sami K. Solanki 1. Introduction ......................................................................59 2. Observations of the Solar Atmosphere ...................................60 3. The Solar Spectrum............................................................61 4. Physics of the Photosphere/Chromosphere..............................65 4.1 One-Dimensional Models.............................................. 65 4.2 Three-Dimensional Models............................................ 70 5. Physics of the Chromosphere/Corona.....................................73 5.1 Coronal Emission and Magnetic Structure........................ 74 5.2 Basic Considerations of the Energetics ............................ 76 5.3 Heating Processes and Modern Models............................ 77 5.4 Connection to the Low Atmosphere ................................ 78 Acknowledgments...................................................................79 References.............................................................................79 CHAPTER 4 Helioseismic Inferences on the Internal Structure and Dynamics of the Sun .........................87 Sarbani Basu and William J. Chaplin 1. Introduction ......................................................................88 2. Theoretical Background ......................................................89 2.1 Equations Governing Solar Oscillations........................... 90 2.2 Properties of Solar Oscillations ...................................... 92 2.3 Relating Frequency Changes to Changes in Structure......... 94 Contents vii 2.4 Effects of Rotation......................................................
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