- Email: [email protected]
Magnetospheric physics
182
BOOK REVIEWS
no mention of lunar radiometric observations. Mutch gives a rather complete description of the Lunar Orbiter photographic system, mission profiles, final pictures, and the associated problems. Tt is rather puzzling and frustrating, however, t h a t he does this without the use of a single Orbiter picture. Despite the above criticisms, Muteh vindicates himself somewhat in the last sentence: "The entire field of 'remote sensing' emerges as one in which instrumental elegance has far outstripped understanding of physical behavior. The potential remains exciting but unrealized." Let us go now to Chapter X, Relative and Absolute Ages of Lunar Materials. E a r ly in the chapter we are given facets of one particular thermal evolution model and then expected, by default evidently, to believe that the conclusions (e.g., melting began 1.5 × 109 years after formation of the moon) reached from that study have special significance. Needless to say, such models are to be looked upon with the utmost suspicion since there are so m a n y hidden assumptions and (when the chapter was written) almost no believable boundary conditions. Continuing on, Muteh gives a good discussion of regolith thickness, including use of the 0 b e r b e e k Quaide morphological classification, but does not note t h a t those authors have shown a good correlation of variations in regolith thickness with crater density and meteoroid flux. We find mention that " A n ingenious remote analysis of the surface layer was performed by Tyler (1968)." W h y wasn't this ingenious bistatic-radar experiment using Explorer 35 given due treatment in the Remote Sensing Chapter? Muteh succinctly summarizes the problems involved in determining relative and absolute ages of lunar surfaces based on observations of crater densities. The follow-on discussion suffers, however, from a lack of the mathematical treatment of the topic (although six of Marcus' rather complete statistical treatments are referenced). Although dozens of curves exist showing relative crater densities for all large maria, many frontside highland regions, and the lunar farside and upon which a good relative time scale can be constructed, Mutch includes only one lunar crater frequeney-~iameter curve (a nondescript one from a 1962 study at that). He presents, however, a diagram showing a lunarwide relative age scale based upon a crater modification (erosion) s e h e m e - - a relatively new technique which has potential merit but which has not yet received a critical review. The last section of the chapter, Chronology for Lunar Events, is a reasonable summary but painful reading for those who are aware of
Apollo sample analysis results, which brings me to the last Chapter, Apollo X I Results. The Apollo results, unfortunately for Muteh, became available near press-time for his book. He felt obligated to include the preliminary results as an appended chapter, with no t e x t revision to earlier chapters (a wise move I suspect). The results reported in this last chapter are so preliminary however, t h a t the material has no current value in light of the detailed published analyses now available. Some statements and explanations are seriously in error or not well understood. For example, the astronauts were not forced to direct the LM 6 km west of the programmed landing site to avoid a rocky surface as the book states (their trajectory was off nearly t h a t much but the astronauts manually redirected the LM only ~600 ft to avoid West Crater). The lack of distinction between radioactive age dates based upon internal mineral isochrons and those based upon whole rock analyses makes it impossible for the uninformed reader to even begin to understand the lunar problem of the "older" soil overlaying "y o u n g er " rocks. Summing up, the good points of Geology of the Moon far outweigh the problems. Its value lies in the uniquely expressed and very readable description of how and why one "does" lunar geology, for which Mutch himself provides the best summary in Chapter X I , Lunar Stratigraphy Reconsidered. I suggest t h a t one read it first. The 324 pages belie the short time it takes to read the book for there is a cumulative equivalent of only ~160 pages of text, double spaced with two inch margins (a reviewer's delight!). The other ~160 pages are superb photographic reproductions and diagrams. At $17.50, I suggest t h a t you encourage your library to buy the book for it has a lasting reference value. I t is m y sincere hope t h a t Muteh will revise the book soon to bring it up to date and to modify or omit the weaker sections. NOEL W . HIN~ERS
Belleomm, Inc. Washington, D.C. 20024
Magnetospheric Physics. Edited by D. J. WILLIAMS and G. D. MEAD. NASA, Greenbelt, Maryland, 1969. 460 pp. Price $10.00. This book is a collection of the invitational review papers t h a t were presented at the International Symposium on the Physics of the Magnetosphere in Washington, D. C. in Septem-
BOOK R E V I E W S
ber 1968. The same set of papers was published in a single issue of Reviews of Geophysics (Feb.-May) in 1969. The book consists of 15 articles, ranging in length from 8 to 50 pages, and an introduction b y the editors. Considering the fact t h a t it is a collection of papers by a number of authors, the book provides an excellent overall view of magnetospheric physics. Further, the book is still very timely, despite the fact t h a t the papers were written over two years ago. The coverage of major magnetospherie phenomena is quite well balanced with 40 pages devoted to the magnetosheath, 98 pages to aurora and polar substorms, 62 pages to the radiation belt, 40 pages to the low-energy plasma in the geomagnetic cavity, and 32 pages to the geomagnetic tail. Other topics include quantitative models of the magnetosphere, the theory of the formation of the radiation belt, low-frequency waves in the magnetosphere, pitch angle diffusion, instabilities in the magnetospheric medium, and magnetospheric convection. An outstanding omission is a review of the studies of fluctuations in the magnetosheath. I n a brief paper on the solar wind interaction with the geomagnetic field, Parker mentions some of the problems related to physics of the magnetosphere and discusses a few of the papers on the subject. Next, the properties of the E a r t h ' s bow shock and the average flow in the magnetosheath are described by Spreiter and Alksne. This very well written paper covers both the theory of the steady state interaction of the solar wind with the geomagnetic cavity and the observations of this interaction. The theoretical model is t h a t of the flow of a perfect dissipationless gas which behaves according to the equations of magnetohydrodynamics. Schindler then discusses laboratory experiments related to the solar wind and the magnetosphere. He describes the usual choices of achievable scaling laws and reviews the results of the laboratory experiments. I n particular, he discusses terrella experiments and the simulation of plasma shocks. He then describes similarities and differences between the results obtained in the laboratory and those obtained in space. l~ext, Roederer reviews various models of the magnetic field in the geomagnetic cavity and compares these models with the observations of the distant field obtained during quiet times. H e also discusses field variations produced by changes in the solar wind pressure. I n a paper on the geomagnetic tail, Ness briefly reviews the knowledge and speculation on the geomagnetic tail as it developed during
183
the period of 1960-1964. He then reviews in considerable detail the results from the extended empirical studies via satellites t h a t began in 1964. H e describes the topology of the tail field and the properties of the plasma sheet. The book includes nearly 100 pages devoted to aurora and polar substorms, consisting of a paper by H u l t q v i s t and one by Feldstein. I n an excellent review, which includes roughly 300 references, H u l t q v i s t compares observations of aurora and polar magnetic storms with present models. After a brief summary of present candidates for the processes of auroral particle acceleration and precipitation in polar substorms, he embarks on an extremely thorough review of the observations. This discussion is unified by comparison with the previously described theoretical models. H e then discusses the energetics of these magnetospheric processes. Finally, he describes likely relationships between auroral zone phenomena and temporal variations in the radiation belt, and between these phenomena and the dynamics of the magnetospheric tail. Feldstein then reviews these same highlatitude phenomena. His approach is to use the behavior and distribution of properties of the auroral oval based on ground observations as tools in the study of the properties of the distant magnetosphere. He discusses the use of the Pi 2 magnetic micropulsations to probe plasma distribution. He also discusses the electric currents associated with polar magnetic substorms and the variations of the magnetic field over the polar caps during such events. Tverskoy then reviews ideas on the formation of the radiation belts. He describes a model in which the charged particles are injected from the geomagnetic tail to the outer magnetosphere during geomagnetic storms. These particles then diffuse inward and undergo corresponding accelerations, the diffusion process being driven by sudden geomagnetic impulses. The particles are then lost from the radiation b e l t - - t h e protons by charge exchange and the electrons by wave particle interactions. Next, Van Allen reviews the work of his group on fluctuations in the intensity of outer zone electrons with energies in the range from 40 keV to several MeV. He also describes their observations of ring current particles, their energies, time profiles of injection, and decay. He argues that the decay rates are consistent with a model in which the process responsible for the decay is charge exchange with atomic hydrogen in the magnetosphere. He then discusses observations of geomagnetically trapped alpha partic.les t h a t bear on the question of whether these radiation
184
BOOK REVIEWS
belt particles are originally of solar wind or ionospheric origin. Next, Vernov et al. review the properties of particles of electrons with energies above 40 keV in the outer radiation belts. They discuss the spectral intensity during quiet times, and the variations during intervals marked by geomagnetic disturbances. The results discussed in t h e review show t h a t new particles first appear in the outer belt near the equatorial plane and then spread gradually to the northern and southern hemispheres as they diffuse inward. In the first phase of a geomagnetic storm, the rate of inward diffusion of these particles is an order of magnitude higher than it is during magnetically quiet periods. Further, the electron intensity in the belt depends on the average level of geomagnetic activity. I t decreases with decreasing activity. They argue, on the basis of the observations obtained to date, t h a t particle injection occurs in the manner described by Tverskoy. In this model, particles are injected into the outer region of the outer belt by the return of lines of magnetic force from the geomagnetic tail to the magnetosphere. This return causes particles to be trapped on these lines of force, and thus transfers particles to the magnetosphere with an accompanying betatron acceleration; they argue further t h a t particle diffusion is effective as close as L = 2.7 where the m a x i m u m of high energy electrons (5-7 MeV) is sometimes observed; that an accelerating mechanism must exist during the period of magnetic storm main phase m a x i m u m ; and that, during magnetically quiet periods, electron diffusion across magnetic shells is the main mechanism forming the belt. Next, Helliwell reviews the properties of electromagnetic waves in the frequency range from l0 s to 105 Hz. He first discusses the properties of waves with sources below the lower edge of the ionosphere. The primary interest here is the study of the manner in which these waves propagate through the magnetosphere. H e then discusses waves called emissions that originate within the magnetosphere. F o r both types he reviews first the empirical knowledge and then the interpretations of these phenomena in terms of some straightforward theoretical models. He emphasizes the importance of studies of these waves to the mapping of magnetospheric parameters. Thus, for example, most ducted propagation from the ground is observed to occur within the plasmasphere. Further, the boundary of the plasmasphere is an especially active region for such waves. He summarizes by describing the distribution of low frequency waves in the geomagnetic meridian
plane on the day side of the E a r t h and by stating some of the outstanding unsolved problems in this area. In a paper on pitch-angle diffusion of t h e geomagnetically trapped radiation belt electrons, Roberts discusses the theory t h a t is based upon the assumption t h a t the F o k k e r - P l a n c k equation is applicable. He then reviews the empirical evidence t h a t diffusion is an important process in the radiation belts, and finally the mechanisms that seem likely to cause the pitch angle scattering that is required to produce this diffusion. These include cyclotron resonance with whistler mode waves, bounce resonance, and resonance with electrostatic oscillations. Gringauz provides a very thorough review of the particles with energies from thermal to 50 keV, in which he covers some 10 years of satellite data. H e includes about 150 references. H e discusses the plasmasphere during both quiet and disturbed times. H e also discusses particles with energies below 40 keV in t h e radiation belts and their relationship to the magnetospheric ring current. He then discusses t h e particle distributions in the plasma sheet of the geomagnetic tail and in the magnetosheath. Next, Kennel also discusses pitch angle diffusion and cyclotron harmonic wave particle interactions as a cause of this diffusion. H e estimates the resulting diffusion coefficients. He then discusses the discontinuities or boundaries in the distributions of electrons and protons in the magnetosphere. He first reviews the evidence for these boundaries and their properties and then argues that they are produced by precipitation from flux tubes as the tubes are convected in from the tail to the earth's night side. Thus, he provides a model for a coupling between convection and precipitation in the magnetosphere. I-Ie then argues that the electron boundary is unstable to micropulsations, thus accounting for the apparent equivalence of the lines of force of the inner edge of the plasma sheet and the lines of force that are associated with extensive Pi 1 micropulsation activity. Finally, he discusses fast radial diffusion, a process t h a t must be faster than the usual mechanisms involving the violation of the third adiabatic invariant in order to account for the injection of protons into the Van Allen belt. I n this connection, he considers the possibility t h a t Bohn diffusion is important. Finally, Axford reviews the state of knowledge of magnetospheric convection. He describes the acceleration of particles by quasi-static electric fields. He reviews the empirical evidence for magnetospheric convection and the argument
BOOK REVIEWS
t h a t field line reconnection is i m p o r t a n t in driving the convection. H e discusses t h e c o n v e c t i o n p a t t e l ~ in t h e o u t e r m a g n e t o s p h e r e a n d its relationship to the r a d i a t i o n belts, t h e aurora, a n d t h e plasmapause. H e t h e n describes t h e u n s t e a d y m a g n e t o s p h e r i e c o n v e c t i o n a n d its relationship to the g e o m a g n e t i c substorms. All in all, t h e book should be quite useful. A n u m b e r of t h e authors h a v e gone to considerable effort to provide e x t e n s i v e lists of references. F u r t h e r , several of t h e m h a v e concisely outlined t h e o u t s t a n d i n g p r o b l e m s in t h e i r p a r t i c u l a r areas of m a g n e t o s p h e r i c physics. PAUL J . COLEMAN, JR.
Dept of Planetary and Space Science Institute of Geophysics and Planetary Physics University of California Los Angeles, California Planets and Life. P. H. A. SNEATH. T h a m e s a n d H u d s o n , L o n d o n W o r l d of Science Library. 216 pp. P r i c e : £1.
This book is an interesting p r e s e n t a t i o n of life, its f u n d a m e n t a l r e q u i r e m e n t s , its origin and distribution in the solar system, a n d some possibilities for deriving i n f o r m a t i o n on the origin and distribution of life t h r o u g h space t r a v e l and interstellar c o m m u n i c a t i o n .
185
The book, in general, comes off r a t h e r well p r i m a r i l y because t h e a u t h o r includes two chapters t h a t are fairly n o v e l a n d t h o u g h t p r o v o k i n g - - C h a p t e r 3 - - T h e N a t u r e of L i v i n g Systems, and Chapter 6 - - A l t e r n a t i v e BiGchemistries. To me, these c h a p t e r s p r o v i d e t h e m a j o r c o n t r i b u t i o n of t h e hook. T h e others are either reasonably well done or fair. T h e book is v e r y well illustrated; however, b y comparison, t h e bibliography is e x t r e m e l y poor, being composed all to often of o u t d a t e d references or none at all. T h e r e a p p e a r to be few factual errors, a l t h o u g h t h e reference to t h e d e t e c t i o n of m e t h a n e a n d a m m o n i a on Mars b y t h e Mariner spacecraft should be corrected. The section on life d e t e c t i o n is c o m p l e t e l y out of date, and in m y opinion, too little a t t e n t i o n is p a i d to t h e c h a p t e r on t h e origin of terrestrial life. The book is a good i n t r o d u c t i o n to w h a t we k n o w a b o u t life in t h e universe, w h a t kinds of research are r e l e v a n t to t h e origin of life, a n d w h a t speculations a b o u t living processes elsewhere in t h e universe are reasonable. The c h a p t e r s m e n t i o n e d a b o v e will be of special interest to people working in t h e field. RICHARD S. YOUNG
Chief, Exobiology, BioScience Programs O~ce of Space Science and Applications N A S A , Washington, D.C. 20546
BOOK REVIEWS
no mention of lunar radiometric observations. Mutch gives a rather complete description of the Lunar Orbiter photographic system, mission profiles, final pictures, and the associated problems. Tt is rather puzzling and frustrating, however, t h a t he does this without the use of a single Orbiter picture. Despite the above criticisms, Muteh vindicates himself somewhat in the last sentence: "The entire field of 'remote sensing' emerges as one in which instrumental elegance has far outstripped understanding of physical behavior. The potential remains exciting but unrealized." Let us go now to Chapter X, Relative and Absolute Ages of Lunar Materials. E a r ly in the chapter we are given facets of one particular thermal evolution model and then expected, by default evidently, to believe that the conclusions (e.g., melting began 1.5 × 109 years after formation of the moon) reached from that study have special significance. Needless to say, such models are to be looked upon with the utmost suspicion since there are so m a n y hidden assumptions and (when the chapter was written) almost no believable boundary conditions. Continuing on, Muteh gives a good discussion of regolith thickness, including use of the 0 b e r b e e k Quaide morphological classification, but does not note t h a t those authors have shown a good correlation of variations in regolith thickness with crater density and meteoroid flux. We find mention that " A n ingenious remote analysis of the surface layer was performed by Tyler (1968)." W h y wasn't this ingenious bistatic-radar experiment using Explorer 35 given due treatment in the Remote Sensing Chapter? Muteh succinctly summarizes the problems involved in determining relative and absolute ages of lunar surfaces based on observations of crater densities. The follow-on discussion suffers, however, from a lack of the mathematical treatment of the topic (although six of Marcus' rather complete statistical treatments are referenced). Although dozens of curves exist showing relative crater densities for all large maria, many frontside highland regions, and the lunar farside and upon which a good relative time scale can be constructed, Mutch includes only one lunar crater frequeney-~iameter curve (a nondescript one from a 1962 study at that). He presents, however, a diagram showing a lunarwide relative age scale based upon a crater modification (erosion) s e h e m e - - a relatively new technique which has potential merit but which has not yet received a critical review. The last section of the chapter, Chronology for Lunar Events, is a reasonable summary but painful reading for those who are aware of
Apollo sample analysis results, which brings me to the last Chapter, Apollo X I Results. The Apollo results, unfortunately for Muteh, became available near press-time for his book. He felt obligated to include the preliminary results as an appended chapter, with no t e x t revision to earlier chapters (a wise move I suspect). The results reported in this last chapter are so preliminary however, t h a t the material has no current value in light of the detailed published analyses now available. Some statements and explanations are seriously in error or not well understood. For example, the astronauts were not forced to direct the LM 6 km west of the programmed landing site to avoid a rocky surface as the book states (their trajectory was off nearly t h a t much but the astronauts manually redirected the LM only ~600 ft to avoid West Crater). The lack of distinction between radioactive age dates based upon internal mineral isochrons and those based upon whole rock analyses makes it impossible for the uninformed reader to even begin to understand the lunar problem of the "older" soil overlaying "y o u n g er " rocks. Summing up, the good points of Geology of the Moon far outweigh the problems. Its value lies in the uniquely expressed and very readable description of how and why one "does" lunar geology, for which Mutch himself provides the best summary in Chapter X I , Lunar Stratigraphy Reconsidered. I suggest t h a t one read it first. The 324 pages belie the short time it takes to read the book for there is a cumulative equivalent of only ~160 pages of text, double spaced with two inch margins (a reviewer's delight!). The other ~160 pages are superb photographic reproductions and diagrams. At $17.50, I suggest t h a t you encourage your library to buy the book for it has a lasting reference value. I t is m y sincere hope t h a t Muteh will revise the book soon to bring it up to date and to modify or omit the weaker sections. NOEL W . HIN~ERS
Belleomm, Inc. Washington, D.C. 20024
Magnetospheric Physics. Edited by D. J. WILLIAMS and G. D. MEAD. NASA, Greenbelt, Maryland, 1969. 460 pp. Price $10.00. This book is a collection of the invitational review papers t h a t were presented at the International Symposium on the Physics of the Magnetosphere in Washington, D. C. in Septem-
BOOK R E V I E W S
ber 1968. The same set of papers was published in a single issue of Reviews of Geophysics (Feb.-May) in 1969. The book consists of 15 articles, ranging in length from 8 to 50 pages, and an introduction b y the editors. Considering the fact t h a t it is a collection of papers by a number of authors, the book provides an excellent overall view of magnetospheric physics. Further, the book is still very timely, despite the fact t h a t the papers were written over two years ago. The coverage of major magnetospherie phenomena is quite well balanced with 40 pages devoted to the magnetosheath, 98 pages to aurora and polar substorms, 62 pages to the radiation belt, 40 pages to the low-energy plasma in the geomagnetic cavity, and 32 pages to the geomagnetic tail. Other topics include quantitative models of the magnetosphere, the theory of the formation of the radiation belt, low-frequency waves in the magnetosphere, pitch angle diffusion, instabilities in the magnetospheric medium, and magnetospheric convection. An outstanding omission is a review of the studies of fluctuations in the magnetosheath. I n a brief paper on the solar wind interaction with the geomagnetic field, Parker mentions some of the problems related to physics of the magnetosphere and discusses a few of the papers on the subject. Next, the properties of the E a r t h ' s bow shock and the average flow in the magnetosheath are described by Spreiter and Alksne. This very well written paper covers both the theory of the steady state interaction of the solar wind with the geomagnetic cavity and the observations of this interaction. The theoretical model is t h a t of the flow of a perfect dissipationless gas which behaves according to the equations of magnetohydrodynamics. Schindler then discusses laboratory experiments related to the solar wind and the magnetosphere. He describes the usual choices of achievable scaling laws and reviews the results of the laboratory experiments. I n particular, he discusses terrella experiments and the simulation of plasma shocks. He then describes similarities and differences between the results obtained in the laboratory and those obtained in space. l~ext, Roederer reviews various models of the magnetic field in the geomagnetic cavity and compares these models with the observations of the distant field obtained during quiet times. H e also discusses field variations produced by changes in the solar wind pressure. I n a paper on the geomagnetic tail, Ness briefly reviews the knowledge and speculation on the geomagnetic tail as it developed during
183
the period of 1960-1964. He then reviews in considerable detail the results from the extended empirical studies via satellites t h a t began in 1964. H e describes the topology of the tail field and the properties of the plasma sheet. The book includes nearly 100 pages devoted to aurora and polar substorms, consisting of a paper by H u l t q v i s t and one by Feldstein. I n an excellent review, which includes roughly 300 references, H u l t q v i s t compares observations of aurora and polar magnetic storms with present models. After a brief summary of present candidates for the processes of auroral particle acceleration and precipitation in polar substorms, he embarks on an extremely thorough review of the observations. This discussion is unified by comparison with the previously described theoretical models. H e then discusses the energetics of these magnetospheric processes. Finally, he describes likely relationships between auroral zone phenomena and temporal variations in the radiation belt, and between these phenomena and the dynamics of the magnetospheric tail. Feldstein then reviews these same highlatitude phenomena. His approach is to use the behavior and distribution of properties of the auroral oval based on ground observations as tools in the study of the properties of the distant magnetosphere. He discusses the use of the Pi 2 magnetic micropulsations to probe plasma distribution. He also discusses the electric currents associated with polar magnetic substorms and the variations of the magnetic field over the polar caps during such events. Tverskoy then reviews ideas on the formation of the radiation belts. He describes a model in which the charged particles are injected from the geomagnetic tail to the outer magnetosphere during geomagnetic storms. These particles then diffuse inward and undergo corresponding accelerations, the diffusion process being driven by sudden geomagnetic impulses. The particles are then lost from the radiation b e l t - - t h e protons by charge exchange and the electrons by wave particle interactions. Next, Van Allen reviews the work of his group on fluctuations in the intensity of outer zone electrons with energies in the range from 40 keV to several MeV. He also describes their observations of ring current particles, their energies, time profiles of injection, and decay. He argues that the decay rates are consistent with a model in which the process responsible for the decay is charge exchange with atomic hydrogen in the magnetosphere. He then discusses observations of geomagnetically trapped alpha partic.les t h a t bear on the question of whether these radiation
184
BOOK REVIEWS
belt particles are originally of solar wind or ionospheric origin. Next, Vernov et al. review the properties of particles of electrons with energies above 40 keV in the outer radiation belts. They discuss the spectral intensity during quiet times, and the variations during intervals marked by geomagnetic disturbances. The results discussed in t h e review show t h a t new particles first appear in the outer belt near the equatorial plane and then spread gradually to the northern and southern hemispheres as they diffuse inward. In the first phase of a geomagnetic storm, the rate of inward diffusion of these particles is an order of magnitude higher than it is during magnetically quiet periods. Further, the electron intensity in the belt depends on the average level of geomagnetic activity. I t decreases with decreasing activity. They argue, on the basis of the observations obtained to date, t h a t particle injection occurs in the manner described by Tverskoy. In this model, particles are injected into the outer region of the outer belt by the return of lines of magnetic force from the geomagnetic tail to the magnetosphere. This return causes particles to be trapped on these lines of force, and thus transfers particles to the magnetosphere with an accompanying betatron acceleration; they argue further t h a t particle diffusion is effective as close as L = 2.7 where the m a x i m u m of high energy electrons (5-7 MeV) is sometimes observed; that an accelerating mechanism must exist during the period of magnetic storm main phase m a x i m u m ; and that, during magnetically quiet periods, electron diffusion across magnetic shells is the main mechanism forming the belt. Next, Helliwell reviews the properties of electromagnetic waves in the frequency range from l0 s to 105 Hz. He first discusses the properties of waves with sources below the lower edge of the ionosphere. The primary interest here is the study of the manner in which these waves propagate through the magnetosphere. H e then discusses waves called emissions that originate within the magnetosphere. F o r both types he reviews first the empirical knowledge and then the interpretations of these phenomena in terms of some straightforward theoretical models. He emphasizes the importance of studies of these waves to the mapping of magnetospheric parameters. Thus, for example, most ducted propagation from the ground is observed to occur within the plasmasphere. Further, the boundary of the plasmasphere is an especially active region for such waves. He summarizes by describing the distribution of low frequency waves in the geomagnetic meridian
plane on the day side of the E a r t h and by stating some of the outstanding unsolved problems in this area. In a paper on pitch-angle diffusion of t h e geomagnetically trapped radiation belt electrons, Roberts discusses the theory t h a t is based upon the assumption t h a t the F o k k e r - P l a n c k equation is applicable. He then reviews the empirical evidence t h a t diffusion is an important process in the radiation belts, and finally the mechanisms that seem likely to cause the pitch angle scattering that is required to produce this diffusion. These include cyclotron resonance with whistler mode waves, bounce resonance, and resonance with electrostatic oscillations. Gringauz provides a very thorough review of the particles with energies from thermal to 50 keV, in which he covers some 10 years of satellite data. H e includes about 150 references. H e discusses the plasmasphere during both quiet and disturbed times. H e also discusses particles with energies below 40 keV in t h e radiation belts and their relationship to the magnetospheric ring current. He then discusses t h e particle distributions in the plasma sheet of the geomagnetic tail and in the magnetosheath. Next, Kennel also discusses pitch angle diffusion and cyclotron harmonic wave particle interactions as a cause of this diffusion. H e estimates the resulting diffusion coefficients. He then discusses the discontinuities or boundaries in the distributions of electrons and protons in the magnetosphere. He first reviews the evidence for these boundaries and their properties and then argues that they are produced by precipitation from flux tubes as the tubes are convected in from the tail to the earth's night side. Thus, he provides a model for a coupling between convection and precipitation in the magnetosphere. I-Ie then argues that the electron boundary is unstable to micropulsations, thus accounting for the apparent equivalence of the lines of force of the inner edge of the plasma sheet and the lines of force that are associated with extensive Pi 1 micropulsation activity. Finally, he discusses fast radial diffusion, a process t h a t must be faster than the usual mechanisms involving the violation of the third adiabatic invariant in order to account for the injection of protons into the Van Allen belt. I n this connection, he considers the possibility t h a t Bohn diffusion is important. Finally, Axford reviews the state of knowledge of magnetospheric convection. He describes the acceleration of particles by quasi-static electric fields. He reviews the empirical evidence for magnetospheric convection and the argument
BOOK REVIEWS
t h a t field line reconnection is i m p o r t a n t in driving the convection. H e discusses t h e c o n v e c t i o n p a t t e l ~ in t h e o u t e r m a g n e t o s p h e r e a n d its relationship to the r a d i a t i o n belts, t h e aurora, a n d t h e plasmapause. H e t h e n describes t h e u n s t e a d y m a g n e t o s p h e r i e c o n v e c t i o n a n d its relationship to the g e o m a g n e t i c substorms. All in all, t h e book should be quite useful. A n u m b e r of t h e authors h a v e gone to considerable effort to provide e x t e n s i v e lists of references. F u r t h e r , several of t h e m h a v e concisely outlined t h e o u t s t a n d i n g p r o b l e m s in t h e i r p a r t i c u l a r areas of m a g n e t o s p h e r i c physics. PAUL J . COLEMAN, JR.
Dept of Planetary and Space Science Institute of Geophysics and Planetary Physics University of California Los Angeles, California Planets and Life. P. H. A. SNEATH. T h a m e s a n d H u d s o n , L o n d o n W o r l d of Science Library. 216 pp. P r i c e : £1.
This book is an interesting p r e s e n t a t i o n of life, its f u n d a m e n t a l r e q u i r e m e n t s , its origin and distribution in the solar system, a n d some possibilities for deriving i n f o r m a t i o n on the origin and distribution of life t h r o u g h space t r a v e l and interstellar c o m m u n i c a t i o n .
185
The book, in general, comes off r a t h e r well p r i m a r i l y because t h e a u t h o r includes two chapters t h a t are fairly n o v e l a n d t h o u g h t p r o v o k i n g - - C h a p t e r 3 - - T h e N a t u r e of L i v i n g Systems, and Chapter 6 - - A l t e r n a t i v e BiGchemistries. To me, these c h a p t e r s p r o v i d e t h e m a j o r c o n t r i b u t i o n of t h e hook. T h e others are either reasonably well done or fair. T h e book is v e r y well illustrated; however, b y comparison, t h e bibliography is e x t r e m e l y poor, being composed all to often of o u t d a t e d references or none at all. T h e r e a p p e a r to be few factual errors, a l t h o u g h t h e reference to t h e d e t e c t i o n of m e t h a n e a n d a m m o n i a on Mars b y t h e Mariner spacecraft should be corrected. The section on life d e t e c t i o n is c o m p l e t e l y out of date, and in m y opinion, too little a t t e n t i o n is p a i d to t h e c h a p t e r on t h e origin of terrestrial life. The book is a good i n t r o d u c t i o n to w h a t we k n o w a b o u t life in t h e universe, w h a t kinds of research are r e l e v a n t to t h e origin of life, a n d w h a t speculations a b o u t living processes elsewhere in t h e universe are reasonable. The c h a p t e r s m e n t i o n e d a b o v e will be of special interest to people working in t h e field. RICHARD S. YOUNG
Chief, Exobiology, BioScience Programs O~ce of Space Science and Applications N A S A , Washington, D.C. 20546