Coronal Expansion and Solar Wind PDF
Preview Coronal Expansion and Solar Wind
Physics and Chemistry in Space Volume 5 Edited by J. G. Roederer, Denver Editorial Board: H. Elsasser, Heidelberg . G. Elwert, Tiibingen L. G. Jacchia, Cambridge, Mass .. J. A. Jacobs, Edmonton N. F. Ness, Greenbelt, Md .. W. Riedler, Graz A. J. Hundhausen Coronal Expansion and Solar Wind With 101 Figures Springer-Verlag Berlin Heidelberg New York 1972 A. J. Hundhausen High Altitude Observatory, National Center for Atmospheric Research*, Boulder, CO/USA * The National Center for Atmospheric Research is sponsored by the National Science Foundation. ISBN -13 :978-3-642-65416-9 e-ISBN -13 :978-3-642-65414-5 DOl: 10.1007/978-3-642-65414-5 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, re production by photocopying machine or similar means, and storage in data banks. Under § 54 of the German Copyright Law, where copies are made for other than private use, a fee is payable to the publisher, the amount of the fee to be determined by agreement with the publisher. © by Springer-Verlag Berlin· Heidelberg 1972. Library of Congress Catalog Card Number 72-85398. Softcover reprint of the hardcover 1st edition 1972 The use of general descriptive names, trade names, trade marks etc. in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. A. J. Hundhausen Coronal Expansion and Solar Wind With 101 Figures Springer-Verlag New York Heidelberg Berlin 1972 A. J. Hundhausen High Altitude Observatory, National Center for Atmospheric Research*, Boulder, CO/USA * The National Center for Atmospheric Research is sponsored by the National Science Foundation. ISBN -13 :978-3-642-65416-9 e-ISBN -13 :978-3-642-65414-5 DOl: 10.1007/978-3-642-65414-5 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, re production by photocopying machine or similar means, and storage in data banks. Under § 54 of the German Copyright Law, where copies are made for other than private use, a fee is payable to the publisher, the amount of the fee to be determined by agreement with the publisher. © by Springer-Verlag Berlin· Heidelberg 1972. Library of Congress Catalog Card Number 72-85398. Softcover reprint of the hardcover 1st edition 1972 The use of general descriptive names, trade names, trade marks etc. in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. Dedicated to My Parents Preface Little more than ten years have passed since spaceprobe-borne instruments con clusively demonstrated the existence of the solar wind. These observations con firmed the basic validity of a theoretical model, first proposed by E. N. Parker, predicting a continuous, rapid expansion of the solar corona. The subsequent decade has seen a tremendous growth in both the breadth and sophistication of solar wind observations; the properties of the interplanetary plasma near the orbit of the earth are now known in great detail. The theory of the coronal ex pansion has also been highly refilled both in the sense of including additional physical processes, and of treating more realistic (time-dependent and non spheri cally-symmetric) coronal boundary conditions. The present volume is an attempt to synthesize the solar wind observations and coronal expansion models from this decade of rapid development. The ultimate goal is, of course, the interpretation of observed solar wind phenomena as the effects of basic physical processes occurring in the coronal and interplanetary plasma and as the natural manifestations of solar properties and structures. This approach implies an emphasis upon the "large-scale" features revealed by the observations. It requires extensive use of the concepts and methods of fluid mechanics. It is the author's intent that this presentation be intelligible to the advanced graduate student or the more experienced scientist unfamiliar with its specialized subject matter. Essential to understanding of the treatment is a grasp of the basic conservation laws of fluid and particle mechanics. Some familiarity with the terminology of solar physics (in particular that describing solar activity) is assumed. Mathematical developments will be held to a minimum. Gaussian-c. g. s. units will be used with two exceptions dictated by prevailing conventions in this field of research. Almost all solar wind observers give solar wind speeds in km sec-1 and interplanetary magnetic flux densities I B I in units of ,),=10-5 gauss. The author's viewpoints regarding the material presented herein were largely formed during his association with the Vela satellite group at the Los Alamos Scientific Laboratory. The collaboration and scientific stimulation of Drs. S. 1. Bame, M. D. Montgomery, and R. A. Gentry of that institution were of incal culable value to the author. Among the influences exerted by colleagues from other institutions, those of Drs. A. Barnes, L. F. Burlaga, D. S. DeYoung, 1. T. Gosling, 1. Hirshberg, N. F. Ness, K. H. Schatten, and 1. M. Wilcox have had the greatest impact upon the ideas set forth here. VIII Preface Special acknowledgements are due to Drs. S. J. Bame and A. J. Lazarus for permission to use unpublished data. The manuscript was typed with diligence and accuracy by Mrs. Ruby Fulk. Its reading by Dr. J. T. Gosling produced abun dant and detailed criticisms to the author's benefit. Final credit must go to my wife Joan, not only for her patience during the struggle, but for application of the mathematical and grammatical reins. October 1972 A. J. Hundhausen Contents Chapter I History and Background I.1 Introduction. . . . . . . . . . . . . . . . . . . . . 1 1.2 Indirect Evidence for the Existence of the Solar Wind . . . 1 1.3 The Extension of the Solar Corona into Interplanetary Space 3 1.4 The Expansion of the Solar Corona into Interplanetary Space. 5 1.5 The Extension of the Solar Magnetic Field into Interplanetary Space 11 1.6 An Alternative Model of the Coronal Expansion . . . . . 14 1.7 Confirmation of the Existence of the Solar Wind by In Situ Spacecraft Observations. . . . . . . . . . . . . . . . 16 Chapter II The Identification and Classification of Some Important Solar Wind Phenomena II.i Introduction....................... 20 II.2 The Classification of Solar Wind Phenomena . . . . . . . . . 21 II.3 An Identification, Description, and Classification of Some Solar Wind Phenomena. . . . . . . . . . . . . 25 Persistent, High-Speed Solar Wind Streams. 25 Flare-Produced Interplanetary Shock Waves 26 Interplanetary Filaments. . . . 28 Alfven Waves . . . . . . . . 29 Hydromagnetic Discontinuities. 30 IIA Summary and Plan of Action. . . 35 Chapter III The Dynamics of a Structureless Coronal Expansion III.1 Introduction. . . . . . . . . . . . . . 36 II1.2 In Search of the Structureless Solar Wind . 37 III.3 The Physical Properties of Low-Speed Solar Wind. 43 III.4 A "One-Fluid" Model of the Steady, Spherically-Symmetric Coronal Expansion . . . . . . . . . . . . . . . . . . 45 x Contents Ill. 5 A "Two-Fluid" Model of the Steady, Spherically-Symmetric Coronal Expansion . . . . . . . . . . . . . . . . . . 49 III. 6 A Comparison of Solar Wind Observations with Predictions of the Basic One-Fluid and Two Fluid-Models . . . . . . . . 53 Ill. 7 The Energetics of the Coronal Expansion . . . . . . . . . 55 IlLS The Effects of Hydromagnetic Waves on th~ Coronal Expansion 61 III.9 The Effects of Magnetic Forces on the Coronal Expansion . . . 66 111.10 The Effects of the Magnetic Modification of Heat Conduction on the Coronal Expansion . . . . . . . . . . . . . . . . . . 67 IlUl The Effects of Viscosity on the Coronal Expansion . . . . . . 71 IlU2 The Effects of Noncollisional Energy Exchange Mechanisms on the Coronal Expansion . . . . . . . . . . . . . . . . . . 74 IlU3 The Effects of a Reduced Thermal Conductivity on the Coronal Expansion. . . . . . . . . . . . . . . . . . . . . 75 111.14 Another Look at the Energetics of the Coronal Expansion SO 111.15 Angular Momentum in the Coronal Expansion S4 111.16 Evaporative Models of the Coronal Expansion . . . . . 90 Chapter IV Chemical Composition of the Expanding Coronal and Interplanetary Plasma IV.l Introduction. . . . . . . . . . . . . . . . . . . . . . .. 94 IV.2 The Determination of the Average Solar Wind Helium Abundance 95 IV.3 A Comparison of the Solar and Interplanetary Helium Abundances 100 IV.4 Theoretical Models of the Expansion ofa Corona Containing Helium . . . . . . . . . . . . . . . . . . . . . . . .. 101 IV.5 The Relationship between the Photospheric and Coronal Helium Abundances . . . . . . . . . . . . . . . . . . . . . .. 107 IV.6 General Conclusions Regarding the Chemical Composition of the Expanding Solar Atmosphere. . . . . . . . . . . . . . . lOS IV.7 Observations of Solar Wind Ions Other than 1 H+ and 4He + + . 109 IV.S The Ionization State of Expanding Coronal Plasma 114 (1) Collisional Ionization by Electron Impact. . . . . . . . 115 (2) Radiative Recombination. . . . . . . . . . . . . . . 115 IV.9 Possible Interplanetary Modification of the Solar Wind Ionization State . . . . . . . . . . . . . . . . . . . . . . . . . .. 119 Chapter V High-Speed Plasma Streams and Magnetic Sectors V.l Introduction ............. . 121 V.2 Observed Features of High-Speed Plasma Streams. 121
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