Solar Wind Acceleration Solar Wind Acceleration By Yuri V. Pisanko, Igor S. Veselovsky and Oleg I. Yakovlev Solar Wind Acceleration By Yuri V. Pisanko, Igor S. Veselovsky and Oleg I. Yakovlev This book first published 2022 Cambridge Scholars Publishing Lady Stephenson Library, Newcastle upon Tyne, NE6 2PA, UK British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Copyright © 2022 by Yuri V. Pisanko, Igor S. Veselovsky and Oleg I. Yakovlev All rights for this book reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. ISBN (10): 1-5275-8180-2 ISBN (13): 978-1-5275-8180-7 TABLE OF CONTENTS Preface ....................................................................................................... vii Chapter 1 ..................................................................................................... 1 Introduction to the problem Eclipses and the solar corona ................................................................. 1 Comets and the solar corpuscular radiation ........................................... 8 Discovery of the solar wind ................................................................. 12 Chapter 2 ................................................................................................... 17 Acceleration region: radio-sounding with spacecraft signals Solar wind velocity .............................................................................. 20 Solar wind density................................................................................ 35 Power and acceleration ........................................................................ 46 Temporal spectra of frequency and amplitude fluctuations ................. 48 The spatial spectrum of plasma inhomogeneities ................................ 56 Radial variation of radio fluctuation intensity and fractional density fluctuations ..................................................................................... 64 The search of wavelike structures ........................................................ 71 Magnetic field estimates from radio-sounding with spacecraft signals ............................................................................................. 78 Summary of Chapter 2 ......................................................................... 80 Chapter 3 ................................................................................................... 83 Solar wind: direct measurements on spacecraft Devices for direct measurements of electric currents and magnetic fields in the solar wind plasma ....................................................... 84 An example of reconstruction of solar wind hydrodynamic parameters from electric current measurements ............................................... 94 Velocity distributions of solar wind components ............................... 102 Solar wind turbulence ........................................................................ 106 Statistics of solar wind velocity, density, temperature, magnetic field, and derivative parameters ................................................... 112 Discontinuities in the solar wind ........................................................ 130 Summary of Chapter 3 ....................................................................... 138 vi Table of contents Chapter 4 ................................................................................................. 143 Theoretical considerations of the acceleration region Evaporation of the corona .................................................................. 144 Magneto-hydrodynamic description of the solar wind ....................... 158 Parker’s model ................................................................................... 163 Relationships between the solar wind and the solar rotation ............. 169 High-speed streams ............................................................................ 195 Coronal mass ejections ...................................................................... 220 Plasma polarization electric field in the acceleration region .............. 228 Summary of Chapter 4 ....................................................................... 239 Chapter 5 ................................................................................................. 243 Aspects we still do not know about the solar wind Why does solar wind exist? ............................................................... 244 Sources and tanks of solar wind matter .............................................. 258 Solar wind acceleration region energetics .......................................... 269 Flight to the Sun ................................................................................. 289 Is it possible to forecast solar wind gusts? ......................................... 294 Summary of Chapter 5 ....................................................................... 302 Bibliography ............................................................................................ 305 References to Chapter 1 ..................................................................... 305 References to Chapter 2 ..................................................................... 308 References to Chapter 3 ..................................................................... 319 References to Chapter 4 ..................................................................... 326 References to Chapter 5 ..................................................................... 334 PREFACE In addition to sunshine, the Sun emits extensively into the interplanetary space of about one trillion tons of ionized hydrogen per second. The phenomenon is known as solar wind. Details of the solar wind acceleration near the Sun are poorly known. The purpose of our book is to elucidate the research of the solar wind acceleration region. Unique scientific information about the solar wind at heliocentric distances up to 3 solar radii obtained from receiving antennas directed almost to the Sun (that is the challenging technical task itself) during telecommunication sessions with “Mars 2”, “Mars 4”, “Venera 10”, “Venera 15”, “Venera 16” spacecraft and the solar wind acceleration region modelling underlie the fundamental basis for our book. The book is based on the lectures given by Oleg I. Yakovlev for postgraduates in the Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, as well as the lectures given by Igor S. Veselovsky for students at the chair of cosmic rays and space physics in Physical Department of Lomonosov Moscow State University and the lectures given by Yuri V. Pisanko for students at the chair of ocean’s thermo-hydromechanics in the Department of Aero-physics and Space viii Preface Research of Moscow Institute of Physics and Technology. The book’s text is not pure lecture notes but rather materials written in preparations for lectures, sometimes not quite suitable for the oral presentation during a lecture. All three courses are directed to familiarize students and postgraduates with the circumsolar “space weather kitchen” physical principles, taking into account the author’s scientific interests. We tried to arrange the book so that each chapter could be read almost separately from the others. It allowed us to introduce the most natural notation system for each chapter: in different chapters, the same symbol could denote different physical or mathematical variables, but inside each chapter, the biunique correspondence between the symbol and the variable (physical or mathematical) remained unchanged. We suppose that a reader knows the fundamentals of electrodynamics, magneto-hydrodynamics, and solar plasma physics, so there are many equations in the text. Not every equation is numbered to avoid unnecessarily burdening the text; numbered are only those mentioned in the text or used in deriving subsequent equations. We introduce abbreviations for an equation (Eq. (X.Y)) or a set of equations (Eqs. (X.Y)) when it is needed to mention these in the text. The first numeral in parenthesis (X) means the chapter number, the second (Y) means the number of the equation (equations) inside the chapter. When assigning a Solar Wind Acceleration ix number to a system of equations, the number stands mainly across the last equation of the system. All variables and equations in the text are written in “italic type”, while vectors are marked by an upper arrow in equations and are written in “bold type” in the text. As a rule, we use the Gaussian system of units everywhere except the cases when the use of other units is dictated by established practice in the area of solar wind research: almost all researchers express the solar wind velocity in kilometres per second while magnetic flux density – in Gauss or SI unit Testa (1 nT = 10–5 Gauss). SI unit Hz is used as the frequency unit. In the section devoted to the electric field in the solar wind acceleration region, we use the SI system of units where the electric field is expressed in Volts per meter and the electric charge – in Coulombs. We use the off-system Angstrom unit for light wavelength and the off-system electron-volt unit for charged particle energy. In Chapter 2, it is convenient to express the heliocentric distance in solar radii. Furthermore, the term “Astronomical Unit (AU)”, which means the average distance between the Sun and the Earth, can be found in the book. We included a few of our papers and books as references. It is stipulated by our desire to touch on subjects well known for us, which are described in detail in our listed publications. We include many references