Physics and Chemistry in Space – serie

The aim of this book is to describe and discuss the aurora as an optical phenomenon, one which can be observed by the naked eye as well as with more sensitive optical detectors. It continues the tradition of study­ ing that impressive and imaginative play of nature, the northern lights, seen and discussed by the Greek philosphers as early as the sixth century B.c. Today the study of the optical aurora is only one of many ways of acquiring information about a major phenomenon: the ejection of plasma from the sun, the interaction of this plasma with the geomagnetic field and the injection of fast particles into the earth's atmosphere. of the optical aurora is justified by the Hence, the separate treatment particular scientific approach: detection and interpretation of electro­ magnetic radiation, approximately in the 1000-100000 A region, produc­ ed through interaction between the auroral particles and the earth's atmosphere. Other techniques, such as radio observations, X-ray observations, direct particle detections from rockets and satellites, studies of magnetic storms, and measurements of the magnetic field and plasma properties in the magnetosphere, are as important or more important than the classical way of studying the optical aurora. Nevertheless, it was felt worthwhile to treat the optical aurora in a separate book, perhaps mainly because today one author cannot master the whole subject with sufficient competence. This book is thus one volume in a series of books giving a more complete picture of physics and chemistry in space.

On attending a conference on the Jovian satellites at UCLA, I heard Lou Lanze­ rotti vigorously present the exciting data on the sputtering of water ice by Me V protons taken with W. L. Brown at AT&T Bell Labs. In his inimitable way he made clear that this new electronic sputtering process was very poorly under­ stood and was very important for surface properties of sattelites. I was immedia­ tely hooked, and have been working ever since with Lanzerotti, Brown, my col­ league at Virginia, John Boring, and Bo Sundqvist at Uppsala on understanding the ejection of material from surfaces and applying laboratory results to intere­ sting planetary problems. In the course of writing this book I also had the benefit of spending a semester with the Planetary Geosciences group in Hawaii, thanks to Tom McCord, a period of time with Doug Nash at JPL, and a period ot time with the group at Catania. The book was started with the encouragement of Lou Lanzerotti. The writing has gone slowly as the field has been changing rapidly. Even now I feel it is incom­ plete, as the interesting Halley dust data have just recently been interpreted in detail, Voyager has recently visited Neptune, and the data on Pluto are rapidly improving. However, most of the principles for plasma ion alteration of surfaces and gases have been established allowing, I hope, a coherent and useful frame­ work for incorporating both new laboratory and planetary data.

An atmospheric phenomenon is considered as 'explained' when we have succeeded in deducing it on the basis of accepted principles of physics. (H. Ertel, Methods and problems of dynamical meteorolo­ gy,p. l) Until recently, noctilucent clouds were regarded merely as a curious atmos­ pheric phenomenon, the occurrence of which aroused only limited scientific attention. However, in the last two decades the interest they have been given has markedly increased. The clouds, usually pale blue in colour, may be seen on a clear night at high latitudes. Typical examples are illustrated in the book. Clouds looking like these in daytime would be classified as cirrostratus. What sets noctilucent clouds apart is their occurrence in the middle of the night, their very obvious pale blue colour, and their disappearance into the dawn close to the onset of civil twilight when the Sun is 6° below the horizon. as being set apart from ordinary Noctilucent clouds were first recognized clouds in 1884/1885 and in a series of sightings that followed their return in the summer of 1885. That year marked the beginning of observations and the interpretation of twilight phenomena. The impetus came from the extraordi­ nary Krakatoa eruption, which was not only one of the most spectacular volcanic eruptions in recorded history, but which also turned out to be a startling event in atmospheric science with repercussions even in our time.

This book presents a review of those efforts that have been and are being made to determine the geochemical composition of the moon and planets. The authors have attempted to present both a review as well as their philosophy about the development of flight experiments for geo­ chemical studies. Their basic premise is that such flight experiments should emphasize the scientific objectives and a total systems approach to meeting these objectives, involving the analytical device, data handling and data interpretation. While the above seems reasonably obvious, many proposals of experiments often tend to begin with an instrument with too little concern about the constraints imposed and whether the data that can be obtained are sufficiently useful to meet the scientific objectives. This book covers the accomplishments in space science exploration, bearing on the history and composition ofthe solar system. 'It also covers the rationale behind the lunar and planetary exploration program. The latter part of the book is concerned with future plans for lunar and planetary exploration instrumentation and techniques in various stages of development. There is an exposition of the methods of remote analysis of the moon and planets, including some concepts developed by the authors as a result of their long term involvement with the space program, from its early inception to the present day preparation for remote geochemical analysis in the Apollo, Mariner and Viking missions.

Since the discovery of geomagnetically trapped radiation by Van Allen in 1958, an impressive amount of experimental information on the earth's particle and field environment has nourished research work for scores of scientists and thesis work for their students. This quest has challenged space-age technology to produce better and more sophisticated instru­ ments and has challenged the international scientific community and governments to establish more, and more effective, cooperative programs of research and information exchange. As a result, an orderly picture of the principal physical mechanisms governing the earth's radiation environment is beginning to emerge. The interest in this topic has reached far beyond the domain of geo­ physics. Indeed, we find trapped radiation elsewhere in the universe: Jupiter's radiation belts, particle trapping in sunspot magnetic fields, cosmic rays confined in interstellar fields and, possibly, ultra-high-energy particles trapped in the magnetic fields of rotating neutron stars. There is abundant technical and scientific literature available on Van Allen radiation; comprehensive reviews are published regularly in journals* or have been collected in book form**, and books have been written on the subject***. The aim of this monograph is to complement the existing literature with a concise discussion of the basic dynamical processes that control the earth's radiation belts. It is mainly intended to help a graduate student or a researcher new to this field to understand the underlying physics and to provide him with guidelines for quantita­ tive, numerical applications of the theory.

In the past two decades a succession of direct observations by satellites, and of extensive computer simulations, has led to the realization that the polar ionosphere plays a principal role in large-scale magnetospheric processes - a manifestation of the physics linkage involved in solar-terrestrial interactions. Spatial/temporal variations in high-latitude electromagnetic phenomena, such as dynamic aurorae, electric fields and currents, have proved to be extremely complex. Now the challenge is to comprehend the vast amount of complicated measurements made in this magnetosphere-ionosphere sysstem of the Earth. This book addresses the electrical coupling between the hot, but dilute, magnetospheric plasma and the cold, but dense, plasma in the ionosphere. In five major chapters, this book presents: - basic properties of magnetosphere-ionosphere coupling; - morphology of electric fields and currents at high latitudes; - global modeling of magnetosphere-ionosphere coupling; - modeling of ionospheric electrodynamics; - current issues, such as auroral particle acceleration, substorms, penetration of high-latitude fields into low latitudes.

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.

Although there are, in addition to the classic but somewhat dated books'l-, some excellent recent books on ionospheric physics and aeronomy'l-... , their scope is quite different from that of the present monograph. This monograph concentrates on the fundamental physical and chemical processes in an idealized planetary ionosphere as a general abstraction, with actual planetary ionospheres representing special cases. Such an approach appears most appropriate for a concise in­ troduction to the field, at a time when increasing experimental in­ formation on the ionospheres of other planets can be anticipated. The main purpose of this monograph, in line with that of the whole series, is to appraise where we stand, what we know and what we still need to know. It is mainly addressed to graduate students and researchers who are in the process of getting acquainted with the field. Within the scope of this monograph it would be impossible to do justice to all relevant publications. Hence, references are somewhat selective and largely limited to the more recent original papers and to authoritative reviews, the latter generally providing also detailed references regarding the historical development of the particular topic. Cgs (gaussian) units are generally used in this book, except where practical units are more appropriate. This book has evolved from a graduate course of the same title which I gave at the Catholic University of America, Washington, D. C.

The underlying kinematical framework of radiation-belt theory is given by the adiabatic theory of charged-particle motion [3J, and the interesting dynamical phenomena are associated with the violation of one or more of the kinematical invariants of adiabatic motion.

In recent years the significant progress in satellite-based observations of plasma states and associated electromagnetic phenomena in space has resulted in the accumulation of much evidence of various plasma instabilities. Today plasma instabilities are believed to be responsible for electromagnetic radiation as well as for many of the macroscopic dynamics of plasmas in space. Most students who begin to study plasma physics are intrigued by the unstable nature of plasmas compared with other states of matter; however, they often become frustrated because there are so many in­ stabilities. Such frustration explains in part why there is no textbook which treats this subject exclusively. A description of plasma instabilities in a systematic way is nontrivial and takes a pertinacious effort. This book is an attempt to provide a basic introduction on the subject and covers most of the important instabilities. However, the author must apologize for any omission of references to contributions of individuals who deserve more credit. The reader is assumed to have a general knowledge of plasma physics obtainable in an undergraduate course. The book is intended to be used as a reference text on the subject of plasma instabilities at the under­ graduate level as well as for a text in a special course in graduate school. Because the book is part of a series on physics and chemistry in space, emphasis is placed on plasma instabilities relevant in space plasmas.

This book resulted from lectures which I gave at the Universities of Kyoto, Cologne, and Bonn. Its objective is to summarize in a unifying way two other­ wise rather separately treated subjects of atmospheric electrodynamics: elec­ tric fields of atmospheric origin, in particular thunderstorm phenomena and related problems on the one hand, and magnetic fields, in particular those which are associated with electric currents of upper atmospheric origin, on the other. Geoelectricity and geomagnetism were not always considered as be­ longing to quite different fields of geophysics. On the contrary, they were re­ cognized by the physicists of the 19th and the beginning of the 20th century as two manifestations of one and the same physical phenomenon, which we pre­ sently refer to as electromagnetic fields. This can still be visualized from the choice of names of scientific journals. For instance, there still exists the Japanese Journal of Geomagnetism and Geoelectricity, and the former name of the present American Journal of Geophysical Research was Terrestrial Magnetism and Atmospheric Electricity. Whereas geomagnetism became the root of modern magnetospheric phys­ ics culminating in the space age exploration of the earth's environment, geo­ electricity evolved as a step-child of meteorology. The reason for this is clear. The atmospheric electric field observed on the ground reflects merely the local weather with all its frustrating unpredictability. The variable part of the geomagnetic field, however, is a useful indicator of ionospheric and magneto­ spheric electric current systems.

The study of very long-distance and around-the-world propagation of HF radio waves becomes more urgent in connection with the problems of long­ distance ground-based radio communications, communications with space­ crafts and satellites, satellite-to-satellite communications, around-the-world radar scanning, around-the-world sounding of the ionosphere, etc. At pre­ sent, these investigations have acquired particular interest because transmit­ ters which make it possible to intentionally modify the ionospheric properties by powerful radio waves have become available. In the case of radio wave propagation over comparatively small distances (about 3000 - 5000 km, one - two hops), in a first approximation, the iono­ sphere can be considered homogeneous in the horizontal direction. The radio wave propagation theory in a horizontally-homogeneous, i. e. , spherically­ symmetric ionosphere was developed with sufficient completeness as early as in the 1920-1940's by Appleton, Ratcliffe, Beynon, Booker, Martyn, and others. This theory is presented in detail in the well-known monographs by Ginzburg (1967), Bremmer (1946), and Budden (1961). Based on this theory, detailed methods for the calculation of radio paths, determination of field amplitude, and interpretation of vertical and oblique ionograms have been developed. All these methods are well-known and widely used in practice, see monographs by Al'pert (1974), Shchukin (1940), and Davies (1969). An altogether different situation takes place in the case of very long-dis­ tance multihop and around-the-world propagation.

The experimental study of magnetospheric processes consists of several disci­ plines or methods, developing in two general directions. The first, internal trend covers the progress in experimental techniques and methods and re­ search specific to this discipline. The other trend combines with other methods in a mutual attempt at understanding the boiling whirlpool of the disturbed magnetosphere. Investigations of auroral X-rays began after Van Allen's (1957) discovery of hard radiation in the upper atmosphere of the auroral zone, and are based on high latitude balloon observations. Scientific apparatus, payload equip­ ment, and particular questions of scientific ballooning are discussed in Chap­ ter 1. Chapter 2 concludes the internal trend of the subject by describing the problems of X-ray generation at the boundary of the atmosphere and propa­ gation downward to balloon altitudes. Auroral X-rays are closely related to most of the processes of the disturbed magnetosphere through energetic auroral electrons; precipitating into the at­ mosphere, the latter create bremsstrahlung photons able to penetrate to an at­ mospheric depth of 10- 20 g cm - 2. In quiet periods auroral electron flux ex­ ists only in embryo, as a hot plasma layer at the inner edge of the plasma sheet: in general it is a transient phenomenon caused by magnetospheric distur­ bances and carrying valuable information of the magnetospheric dynamics.

Spacecraft study of the Solar system is one of humanity's most outstanding achievements. Thanks to this study, our present knowledge of properties of and conditions on the planets exceeds many-fold that of 20 years ago: planets have been rediscovered. This is especially the case for planetary atmospheres, whose properties were for the most part either not at all or only erroneously known. Much research has been invested in the study of the atmospheres of Mars and Venus, and their chemical composition and photochemistry are basic problems in these studies. In the present publication I have tried to summarize all findings in this field. The English version of the book includes new data in the field from the last 3 years since the book was published in Russian. I wish to thank U. von Zahn, who initiated my talks with Springer-Verlag and acted as technical editor. December 2, 1985 V. A. KRASNOPOLSKY Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Chemical Composition and Structure of the Martian Atmosphere 4 1. 1 Carbon Dioxide and Atmospheric Pressure . . . . . . . . . . . . . . . . . . . 4 1. 2 CO and O Mixing Ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2 1. 3 Ozone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. 4 Water Vapor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1. 5 Composition of the Upper Atmosphere as Determined from Airglow Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1. 6 Mass Spectrometric Measurements of the Atmospheric Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 31 1. 7 Ionospheric Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 1. 8 Temperature Profile of the Lower Atmosphere. . . . . . . . . . . . . . . . 36 1. 9 Temperature of the Upper Atmosphere . . . . . . . . . . . . . . . . . . . . . . 40 1. 10 Eddy Diffusion Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2 Photochemistry of the Martian Atmosphere . . . . . . . . . . . . . . . . . .

One of the most fundamental discoveries of the solar system was the detection of four moons in orbit around Jupiter by Galileo Galilei in 1610. The discovery was significant not only in the context of Jupiter; it gave credence to and was instrumental in firmly establishing the heliocentric system of Nicolaus Copernicus. Almost four centuries after Galileo's discovery, exten­ sive observations by the two Voyager spacecrafts have once again revolu­ tionized our thinking about the major planets, their composition, structure, origin, and evolution. This book is an attempt at summarizing our present understanding of the atmospheres and ionospheres in the outer solar system, with particular emphasis on the relevant physics and chemistry. I was motivat­ ed to prepare this manuscript for the following reasons. First, after under­ going rapid expansion in the recent past, the subject has finally attained suf­ ficient maturity to warrant a monograph of its own. Second, I have felt that as a result of recent observations, new and challenging problems have arisen whose resolution requires unconventional analysis and theoretical interpreta­ tion of existing data, as well as the collection of new kinds of data. I believe the time is ripe to put these issues in the appropriate scientific perspective, with the hope of stimulating novel theoretical, observational, and laboratory studies. I have highlighted the significant scientific problems throughout the book, especially at the end of each chapter.

During the 30 years of space exploration, important discoveries in the near-earth environment such as the Van Allen belts, the plasmapause, the magnetotail and the bow shock, to name a few, have been made. Coupling between the solar wind and the magnetosphere and energy transfer processes between them are being identified. Space physics is clearly approaching a new era, where the emphasis is being shifted from discoveries to understanding. One way of identifying the new direction may be found in the recent contribution of atmospheric science and oceanography to the development of fluid dynamics. Hydrodynamics is a branch of classical physics in which important discoveries have been made in the era of Rayleigh, Taylor, Kelvin and Helmholtz. However, recent progress in global measurements using man-made satellites and in large scale computer simulations carried out by scientists in the fields of atmospheric science and oceanography have created new activities in hydrodynamics and produced important new discoveries, such as chaos and strange attractors, localized nonlinear vortices and solitons. As space physics approaches the new era, there should be no reason why space scientists cannot contribute, in a similar manner, to fundamental discoveries in plasma physics in the course of understanding dynamical processes in space plasmas.

Physics of the Inner Heliosphere gives for the first time a comprehensive and complete summary of our knowledge of the inner solar system. Using data collected over more than 11 years by the HELIOS twin solar probes, one of the most successful ventures in unmanned space exploration, the authors have compiled 10 extensive reviews of the physical processes of the inner heliosphere and their connections to the solar atmosphere. Researchers and advanced students in space and plasma physics, astronomy, and solar physics will be surprised to see just how closely the heliosphere is tied to the sun and how sensitively it depends on our star. The four chapters of Volume I of the work deal with large-scale phenomena: - observations of the solar corona - the structure of the interplanetary medium - the interplanetary magnetic field - interplanetary dust.

Physics of the Inner Heliosphere gives for the first time a comprehensive and complete summary of our knowledge of the inner solar system. Using data collected over more than 11 years by the HELIOS twin solar probes, one of the most successful ventures in unmanned space exploration, the authors have compiled six extensive reviews of the physical processes of the inner heliosphere and their relation to the solar atmosphere. Researchers and advanced students in space and plasma physics, astronomy, and solar physics will be surprised to see just how closely the heliosphere is tied to, and how sensitively it depends on, the sun. Volume 2 deals with particles, waves, and turbulence, with chapters on: - magnetic clouds - interplanetary clouds - the solar wind plasma and MHD turbulence - waves and instabilities - energetic particles in the inner solar system

In the years since the pioneering efforts of Sir Edward Appleton, M. A. F. Barnett, G. Breit, and M. A. Thve, many radio techniques have been employed to investigate the terrestrial ionosphere. The purposes of this book are to exam­ ine the basic physical interaction process of radio waves with the ionosphere, scrutinize each of the radio techniques currently in use, and describe the elements of each technique, as well as assess their capabilities and limitations. I have included some of the history of each technique, since we often tend to forget the efforts of the "pioneers". The interaction of radio waves with the terrestrial ionosphere has been described in considerable detail in several "classic" treatments, e.g., Ratcliffe (1959), Al'pert (1963), Budden (1961) and Davies (1965), Rishbeth and e.g., Flock (1979), Davies Garriott (1969), and in other more recent books, (1990), Hargreaves (1979), and Budden (1985). A few of the radio techniques have been described by Hargreaves (1979) and a book by Giraud and Petit (1978) has also included discussion of several of the techniques. The "WITS" handbook No. 2 (1989) also contains description of several radio techniques.

This book is a study of plasma waves which are observed in the earth's magnetosphere. The emphasis is on a thorough, but concise, treatment of the necessary theory and the use of this theory to understand the manifold varieties of waves which are observed by ground-based instruments and by satellites. We restrict our treatment to waves with wavelengths short compared with the spatial scales of the background plasma in the mag­ netosphere. By so doing we exclude large scale magnetohydrodynamic phenomena such as ULF pulsations in the Pc2-5 ranges. The field is an active one and we cannot hope to discuss every wave phenomenon ever observed in the magnetosphere! We try instead to give a good treatment of phenomena which are well understood, and which illustrate as many different parts of the theory as possible. It is thus hoped to put the reader in a position to understand the current literature. The treatment is aimed at a beginning graduate student in the field but it is hoped that it will also be of use as a reference to established workers. A knowledge of electromagnetic theory and some elementary plasma physics is assumed. The mathematical background required in­ cludes a knowledge of vector calculus, linear algebra, and Fourier trans­ form theory encountered in standard undergraduate physics curricula. A reasonable acquaintance with the theory of functions of a complex vari­ able including contour integration and the residue theorem is assumed.

The geomagnetic field observed on the surface of the earth has been an important source of information on the dynamic behavior of the magnetosphere. Because the· magnetosphere and its environment are filled with plasma in which electric current can easily flow, dynamic processes that occur in the magnetosphere tend to produce perturba­ tions in the geomagnetic field. Geomagnetic data have therefore pro­ vided valuable means for sensing the processes taking place at remote locations, and such basic concepts as the magnetosphere, solar wind, and trapped radiation were derived in early, presatellite days from geomagnetic analyses. Because of this advantage, geomagnetic observations have been widely utilized for monitoring the overall condition of the magneto­ sphere. Although the advent of space vehides has made it possible to observe magnetospheric processes in situ, supplementary information on the overall magnetospheric condition is frequently found to be indispensable for interpreting these observations in the proper perspec­ tive. Hence for magnetospheric physicists involved in various branches of the field it has become a common practice to employ geomagnetic data as a basic diagnostic tool.

The subject of geomagnetic micropulsations has developed extremely rapidly and it is difficult to know when is an appropriate time to pause and assess the sum total of our knowledge-both observational and theoretical. There has in recent years been a tremendous increase in both the quantity and quality of data and also many theoretical ad­ vances in our understanding of the phenomenon. Undoubtedly there will be further progress in both areas but it seems worthwhile now to review both our knowledge and our ignorance. This book was essen­ tially completed by the end of April 1969 and tries to give a summary of the subject up to that time. The Earth is enclosed in the magnetosphere, a hollow carved out of the solar wind by the Earth's magnetic field. Above the ionosphere there is a very tenuous thermal plasma of partially ionized hydrogen in diffusive equilibrium with magnetic and gravitational forces, and ener­ getic protons and electrons that constitute the trapped Van Allen ra­ diation belts. Throughout this anisotropic and inhomogeneous plasma, natural and man-made electromagnetic energy propagates in a wide variety of modes and frequency bands. This book is concerned with that class of natural signals called geomagnetic micropulsations-short period (usually of the order of seconds or minutes) fluctuations of the Earth's magnetic field.

Nonlinear effects in the ionosphere (cross modulation of radio waves) have been known since the 1930s. Only recently, however, has the rapid increase in the power and directivity of the radio transmitters made it possible to alter the properties of the ionosphere strongly and to modify it artificially by applying radio waves. This has revealed a variety of new physical phenomena. Their study is not only of scien­ tific interest but also undisputedly of practical interest, and is presently progressing very rapidly. This monograph is devoted to an exposition of the present status of theoretical research on this problem. Particular attention is paid, naturally, to problems in the development of which the author himself took part. It is my pleasant duty to thank V. L. Ginzburg, L. P. Pitaevskii, V. V. Vas'kov, E. E. Tsedilina, A. B. Shvartsburg, and Va. S. Dimant for useful discussions and for valuable remarks during various stages of the work on the problem considered in this book. Contents 1. Introduction . . . . . . . . . . . . . . . . . . .