COSMIC RAYS IN INTERPLANETARY MAGNETIC FIELDS

Transcription

1 COSMIC RAYS IN INTERPLANETARY MAGNETIC FIELDS

2 GEOPHYSICS AND ASTROPHYSICS MONOGRAPHS Editor B. M. McCORMAC, Lockheed Palo Alto Research Laboratory, Palo Alto, Calif., U.S.A. Editorial Board R. GRANT ATHA Y, High Altitude Observatory, P. O. Box 3000, Boulder, CO 80307, U.S.A. PETER BANKS, Radioscience Laboratory, Stanford University, Stanford, CA 94305, U.S.A. DONALD M. HUNTEN, Department of Planetary Science, University of Arizona, Tucson, AZ 85721, U.S.A. MAX KUPERUS, University of Utrecht, Sonnenborgh Observatory, Zonnenburg 2, 3512 NL Utrecht, The Netherlands REIMAR LUST, Director General ESA,.8-1D, rue,maris-nikis, Paris Cedex 15, France ROBERT ROSNER, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A. GILBERT WEILL, Institut D'Astrophysique, 98 Bis Boulevard Arago, Paris, France

3 I. N. TOPTYGIN Department of Theoretical Physics, M. I. Kalinin Poly tech nical Institute, Leningrad, USSR COSMIC RAYS IN INTERPLANETAR Y MAGNETIC FIELDS Translated by D. G. Yakovlev D. REIDEL PUBLISHING COMPANY A MEMBER OF THE KLUWER ACADEMIC PUBLISHERS GROUP DORDRECHT I BOSTON I LANCASTER /TOKYO

4 Library of Congress Cataloging in Publication Data Toptygin, I. N. (Igor' Nikolaevich) Cosmic rays in in terplanetary magnetic fields. (Geophysics and astrophysics monographs) Translation of: Kosmicheskie luchi v mezhplanetnykh magnetnykh poliakh. Bibliography: p. Includes index. 1. Magnetic fields (Cosmic physics) 2. Solar cosmic rays. I. Title. II. Series. QC809.M25T ISBN-13 : e-isbn-13 : DOl: / Published by D. Reidel Publishing Company, P.O. Box 17, 3300 AA Dordrecht, Holland. Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 190 Old Derby Street, Hingham, MA 02043, U.S.A. In all other countries, sold and distributed by Kluwer Academic Publishers Group, P.O. Box 322,3300 AH Dordrecht, Holland. English translation from the Russian edition: KOCMflllecKHe nyqw B Me)KIIJIaHeTHbIX MarnHTIIbIX ITollilX The English edition contains additional material, making this an updated edition. All Rights Reserved Original 1983, Nauka, Moscow English edition 1985 by D. Reidel Publishing Company, Dordrecht, Holland Softcover reprint of the hardcover 1st edition 1985 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner

5 TABLE OF CONTENTS PREFACE PREFACE TO THE ENGLISH EDITION xi xiii CHAPTER I: PHYSICAL PROPERTIES OF THE INTERPLANETARY MEDIUM 1. The Solar Wind Observational Data on the Solar Wind Origin of the Solar Wind Interaction of the Solar Wind with the Interstellar Medium 8 2. Large-scale Interplanetary Magnetic Fields Observational Data on Large-scale Interplanetary Magnetic Fields and their Association with Magnetic Fields on the Sun 2.2. Theory of Interplanetary Magnetic Fields and Comparison with Experiment 3. Oscillations and Waves in Solar Wind Plasma 3.1. Disturbances of the Interplanetary Medium 3.2. Theory of MHD Waves in the Non-uniform Solar Wind 3.3. Observational Data on MHD Waves 4. Shocks and Discontinuities in the Interplanetary Medium 4.1. Possible Types of MHD Shocks and Discontinuities in Interplanetary Plasma 4.2. Observational Data on MHD Shocks and Discontinuities the Solar Wind Plasma 5. Spectral Description of Stochastic Magnetic Fields 5.1. Correlation Tensors of Stochastic Magnetic Fields 5.2. Spectra of Magnetic Fields and Plasma Parameters 5.3. On the Theory of Solar Wind Turbulence CHAPTER II: THEORY OF FAST PARTICLE MOTION IN INTERPLANETARY MAGNETIC FIELDS Qualitative Picture of Fast Particle Motion in Interplanetary Space KInetic Equation for Particles Moving in Magnetic Fields with Small-scale Inhomogeneities Initial Equation and Basic Approximations Averaging over Small-scale Magnetic Fields Kinetic Equation. The Case of Small-scale Inhomogeneities 90 the in

6 vi TABLE OF CONTENTS 8. Transport Equation Diffusion Approximation. Convective Transport and Adiabatic Variation of Particle Energy Transport Equation for Scattering of Particles on MHD Discontinuities and Magnetic Clouds Second-order Acceleration Effects for Regular Large-scale Plasma Motions Derivation of the Transport Equation on the Basis of Drift Approximation Scattering and Transport of Particles in Strong Magnetic Fields Averaging over Particle Rotations Round Magnetic Field Lines and Over Large-scale Random Magnetic Fields Evaluation of Pitch-angle Diffusion Coefficient Diffusion Equation. Longitudinal Diffusion Coefficient Transverse Diffusion Coefficient Evaluation of Diffusion Coefficient from Experimental Data on Spectra of Magnetic Fluctuations and Comparison with Experiment 134 CHAPTER III: PROPAGATION OF ENERGETIC SOLAR PARTICLES Basic Observational Data on Energetic Particles 6f Solar Origin Overall Data Abundance of Energetic Solar Particles (Nucleon Component) Events Enriched by He and Heavy Elements Spectra of Energetic Solar Particles Temporal Rises of Energetic Solar Particle Intensity Anisotropy of Low-energy Solar Protons Coronal Propagation Quasi-stationary Background of Low-energy Particles in Interplanetary Space Anomalous Component Solar Electrons Total Energy of Particles Accelerated in Solar Flares II. Anisotropic Propagation of Solar Cosmic Rays Stationary Propagation of Particle Streams with Large Anisotropy Temporal Variation of Intensity for Large Particle Transport Paths Scattering at pitch Angles Close to ~/2. Coherent Propagation of Solar Particles Numerical Simulations of Solar Proton Propagation Stationary Transport 6f Solar Cosmic Rays Diffusion and Convection of Solar-flare Cosmic Rays Transport of Non-relativistic Protons Temporal Variation of Anisotropy Numerical Simulations of Transport of Solar-flare Particles with Allowance for Convection and Adiabatic Deceleration 183

7 TABLE OF CONTENTS vii CHAPTER IV: PARTICLE ACCELERATION PROCESSES IN INTERPLANETARY SPACE 14. Observational Data on Energy Variations of Cosmic Rays in Interplanetary Space Observations of Adiabatic Particle Deceleration Basic Data on Acceleration Processes in Interplanetary Space Particle Acceleration in Corotating High-speed Streams Anomalous Component Acceleration Particle Acceleration in Planetary Magnetospheres Particle Acceleration at the Heliomagnetosphere Boundary Particle Acceleration Due to Random Plasma Motions: Fermi Mechanism Particle Acceleration in the Moving Cloud Model Acceleration Due to Large-scale Motions of the Medium Particle Acceleration by Gyrotropic Turbulence Particle Acceleration bymhd Turbulence Acceleration by Small-scale Fields. Energy Diffusion Acceleration of Non-confined and Confined Particles by Large-scale Fields List of Main Results Estimates of the Turbulent Acceleration Coefficient in Interplanetary Space Formation of Spectra of Accelerated Particles Spectra of Particles Accelerated by MHD Turbulence Non-stationary Acceleration in a Uniform System Acceleration with Account for Spatial Diffusion Effect of Acceleration on Transport of Solar Protons The Effects of Adiabatic Losses and Acceleration Joint Account for Adiabatic Losses, Acceleration and Spatial Diffusion Particle Acceleration in the Magnetosphere of Jupiter Acceleration and Transport of Particles by MHD Shocks Fast Particle Interaction with Shock Front: Acceleration, Reflection and Crossing Fermi Acceleration of Particles Near a Shock in a Turbulent Medium. Boundary Conditions for Fast Particles at MHD Shock Fronts Acceleration and Transport of Solar-flare protons by Interplanetary Shocks (Diffusion Model) Monte Carlo Simulations of Proton Transport by Shocks Short-term Enhancements with Large Anisotropies and Soft Spectra Proton Acceleration to Relativistic Energies in Interplanetary Space Acceleration of Particles from the Uniform Background and Formation of the "Universal" Spectrum of Cosmic Rays

8 viii TABLE OF CONTENTS IS.S. Generation of Turbulence by Accelerated Particles near Interplanetary Shock Fronts IS.9. The Role of Energy Losses and Particle Injection into the Regime of Acceleration by a Shock IS.10. The Effect of Accelerated Particles on Shock Front Structure IS.II. Fast Particle Acceleration by a Moving Spherical Shock 27S 2S CHAPTER V: MODULATION OF GALACTIC COSMIC RAYS Basic Observational Data on Galactic Cosmic Rays Abundances of Galactic Cosmic Rays Energy Spectra of Primary Cosmic Rays Intensity Variations of Galactic Cosmic Rays Due to Interaction with Interplanetary Magnetic Fields year Variation day Variations Forbush Decreases Short-term Variations (Intensity Fluctuations) of Cosmic Rays Anisotropy of Galactic Cosmic Rays Radial and Latitudinal Gradients of Galactic Cosmic Rays Theory of Galactic Cosmic Ray Modulation by Solar Hind Magnetic Field The Diffusion-convection Model The Effect of Drifts in Non-uniform Interplanetary Magnetic Fields on Modulation of Galactic Cosmic Rays Particle Acceleration in the Region where the Solar Hind Interacts with the Interstellar Medium Short-term Variations of Cosmic Ray Intensity The Sources of Short-term Cosmic Ray Variations Equation for Two-particle Distribution Function Intensity Fluctuations of High-energy Cosmic Rays Equation for Two-particle Distribution Function in the Drift Approximation Fluctuations of Moderate-energy Particles Comparison with Experiment 330 CONCLUDING REMARKS 332 APPENDICES 336 I. The Green Function of the Stationary Transport Equation 336 II. Solution to Non-stationary Transport Equation for a Constant Diffusion Coefficient 339 III. Adiabatic Invariant of Charged Particle Crossing a Transverse Shock 340 IV. Adiabatic Invariant of Charged Particle Crossing an Ob lique Shock 342 REFERENCES 349 INDEX 371

9 To the memory of Academician Sergej Vernov, an outstanding person and scientist, whose contribution to the investigation of cosmic rays is enormous

10 PREFACE Fast particles of natural or1g1n (cosmic rays) have been used for a long time as an important source of astrophysical and geophysical information. A study of cosmic ray spectra, time variations, abundances, gradients, and anisotropy provides a wealth of data on physical conditions in the regions of cosmic ray generation as well as in the media through which cosmic rays propagate. Astrophysical aspects of cosmic ray physics have been considered in a number of monograpqs. The most detailed seems to be "The Origin of Cosmic Rays" by V. L. Ginzburg and S. 1. Syrovatskij (1964) which is, however, concerned mainly with galactic cosmic rays. The physics of the circumsolar space is discussed in this book only rather briefly. Several other monographs have been devoted mostly to the physics of the interplanetary medium and cosmic rays in interplanetary space. These include the books by Dorman (1963, 1975a, b), Parker (1963), Dorman and Miroshnichenko (1968). The present monograph differs from the above mentioned books in two main aspects: (i) It presents a unified theoretical approach to analys{ng the properties of fast particles in interplanetary space, based upon consideration of cosmic rays as a highly energetic component of the interplane~ary plasma, which makes use of the plasma physics methods to describe the behaviour of cosmic rays. (ii) It includes a large amount of new data which has not yet been described in the review literature. The monograph reviews important recent experimental and theoretical results which have so far appeared as original publications only, particularly, the results obtained by the author and his colleagues. The main subject of the monograph, theoretical and experimental aspects of energetic particle propagation in interplanetary space, is presented after a short consideration of the physical properties of the interplanetary medium upon which the subsequent theory is based. In this part, particularly, the latest data on the solar wind and interplanetary magnetic field in the outer heliosphere and on the relation between coronal and interplanetary fields are described. The theory of galactic and solar cosmic ray propagation is developed on the basis of up-to-date kinetic theory of charged particle motions in random fields. The theory of energetic particle propagation (including particle drifts, multiple scattering and convective transport), together with the energy exchange processes between energetic particles xi

11 xii PREFACE and interplanetary plasma (adiabatic losses, particle acceleration by macroscopic plasma motions, low-amplitude MHD waves and shocks), is considered in the frame of the unified formalism based upon the Boltzmann kinetic equation and theory of random functions. In particular, the monograph discusses the following recently developed problems: acceleration and transport of energetic particles by shocks; particle acceleration by supersonic turbulence; acceleration in corotating streams in the outer heliosphere; coherent propagation of solar cosmic rays; the effect of acceleration in interplanetary space on transport of solar protons; particle acceleration at the boundary between the solar wind and the interstellar medium; the anomalous component of cosmic rays; the effect of drifts on the modulation of galactic cosmic rays. A detailed discussion of observational aspects of the above phenomena is presented along with the theory; theoretical conclusions are compared with the results of measurements. The author has made an attempt to present the most significant published results concerned with energetic particles in interplanetary space available up to the middle of 1981, including the results presented at the XVIIth International Cosmic Ray Conference (Paris, July 1981). Nevertheless, more than a few interesting problems which do deserve attention probably remain unmentioned by the author, who apologises most sincerely to those of his colleagues whose work he has been unable to discuss properly in this book, for one reason or another. The author hopes tha-t the book will be helpful for a wide enough circle of specialists in the field of cosmic ray physics, solar physics, geophysics, astrophysics, and space physics. Some results may be of interest for those whose fields are theoretical physics or plasma physics. The book is written in such a way as to be accessible even to readers who wish to be acquainted with the subject from the very beginning, particularly for undergraduates and postgraduates of related fields. Some parts of the monograph have been used in work with students who specialize in cosmic physics and with postgraduates at the M. I. Kalinin Leningrad Poly technical Institute. The author's thanks are due to Academician S. N. Vernov for continuous support of this work and to N. F. Pisarenko, the referee of the book, for valuable advice concerning improvement of the material included, especially the observational data. Leningrad December 1981 I. Toptygin

12 PREFACE TO THE ENGLISH EDITION The English edition of the monograph, which is published two years after the Russian one, includes new data. While making these additions, I have attempced to review the most important results obtained recently in the field of study and published in the scientific literature, including those reported at the XVIII International Cosmic Ray Conference (Bangalore, August-September 1983). In particular, I have added the latest observational results on particles of solar origin as well as on the cosmic ray acceleration and propagation processes in the heliomagnetosphere. Rather large addenda have also been made to Chapter I; they are mainly devoted to the solar wind properties, large-scale magneto-plasma structures and solar wind turbulence. In addition, I have included some earlier results which seem to have aroused great interest in recent years. These are the theoretical estimates of non-linear MHD wave damping ( 3.2) and the elements of cosmic ray drift theory ( 8.4). It is a pleasure to recognize that the book, published in English by D. Reidel Publishing Company, will be more accessible to English-speaking readers and, in particular, to young researchers. I hope that the book represents a useful contribution to urgent problems of cosmic physics which have been the subject of active and cooperative studies by many scientists from different countries. Leningrad February 1984 I. Toptygin xiii