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Physics and dynamics of meteors, I.A.U. symposium
Planet. Space SoL 1969, Vol. 17, pp. 1435 to 1436. Pergamon Prcas. Printed in Northern Ireland
BOOK REVIEWS
L. KRES,~Cand F. M. MILt.t~N (Editors) : Physics and Dynamics of Meteors, LA.U. Symposium No. 33. Reidel, Dordrecht-Holland, 1968. xiii + 525 pp. 90 fls. Tim SYMPOSIUM,held in September 1967 at Tatranska Lomnica, Czechoslovakia, reflects the enormous shift of the meteor observational work into the realm of radar, the formerly dominant visual and photographic methods now acquiring but an auxiliary significance. The rapidly developing physical and dynamical theory supplements and interprets the factual material. Geographically, there is also a conspicuous shift--to the East, only partly due to the choice of the host country. Of the 50 papers, 14 belong to Czechoslovakia, 14 to Russia, 8 to the United States, 5 to Canada, 3 to England, 2 to Italy, and one each to Australia, East Germany, Japan and Sweden. The papers represent a fair cross section of current meteor research, from interplanetary dust to 'ordinary' meteors in the gram range of mass. Meteorites and cratering are not included. Most papers are well presented, often containing basic new material, with Abstracts and proper definitions of the terminology. However, some of the contributions are erring in this respect, thus unnecessarily impeding the reading. Introduced by 9 survey papers, the contributions are concerned with the derivation of the distribution of the masses, chemical composition, velocities, orbital elements and their changes, separately in different size classes of the meteors. They also deal with physical processes of meteor flight through the atmosphere. A few of the conclusions may be mentioned---as a sample of the contents. From 3200 radar records with the oblique-scattering method (Andrianov et al., p. 14), seasonal distributions of meteor flux over the celestrial sphere reduced to a constant limiting mass, as well as the distribution of velocities are derived. Meteor radar observations point to a variation of atmospheric density at 90--110 km level with the solar cycle, with density maximum at solar mininaum; the variation is opposite in phase to that of the uppermost atmosphere as deduced from satellite drag 03. A. Lindblad, p. 50). At Tokyo Astronomical Observatory, since 1963 a total of 79 meteor spectra have been obtained, of these 10 for sporadic meteors. A Leonld spectrum showed 73 identified lines including the forbidden oxygen 5577 A (Hi.rose et aL, p. 105). Telescopic meteors despite their smallness penetrate deeper into the atmosphere than the visual dustballs, reaching an endpoint at 81 km (Kohoutek, p. 143). This confirms former observations and seems to imply that they are compact grains not dustballs., Diffusion of ionized meteor trains can be inhibited by the Earth's magnetic field only ff the angle is less than 1° with the field direction (T. R. Kaiser, p. 161). From radar echo duration of night and daytime meteors, negative ion attachment rates are estimated and dissociative attachment to ozone (08 + e -* O- + Oi) is suggested (P. Gl6de, p. 175). Statistics of radar meteor orbits, based on 2500 orbits obtained at Jodrell Bank and 12500 orbits from Kharkov, U.S.S.R. (V. N. Lebedine~, p. 241), as compared with the more massive photographic meteors, reveals remarkable differences. At a mass limit of 0.001 g, the orbital inclinations are more nearly random, with many around 90 ° and retrograde (90-180°), while the more massive meteors show low inclinations and few retrograde orbits. Fireballs from the Prairie Network seem to point to a low average density of 0.4 g/cm 8 for the meteoroids, more or less the same as for dusthalls (R. E. McCrosky, p. 265), The difference, however, is in fragmentation and the conclusion may need revision because of the complexity of the ablation and deceleration phenomena in the deeper atmosphere. The micrometeorite flux in the neighbourhood of the Earth may be lower by some three orders of magnitude than recent acoustic sensor data have indicated (Nilsson and Southworth, p. 280); the so-called 'dust belt' may be non-existent. Theoretical models are proposed for the distribution of sporadic streaming of 1500 radar echoes over the celestial sphere (Carrara et al., p. 288). From the 13th century Chinese Encyclopaedia of Ma Touan-lin and other sources, published by E. Biot in 1848, fireball radiants have been deduced (Astapovi~ and Terent'eva, p. 308) which help to follow up the history of past meteor showers. The Perseids have appeared in 830 A.D. with a radiant displaced 20° from its present position. The Leonids have been there for all the time of the Chinese records. In all, seven of the present great showers were identified plus some 80 more or less certain radiants of minor showers. A thorough review of The Interplanetary Dust Cloud is presented by T. R. Kaiser (p. 325). 1435
1436
BOOK REVIEWS
A number of papers is devoted to the derivation of the meteor mass distrubution, represented as a power law. In the form R-,dR of the frequency of radii, the radar data point top from 2.5 to 5"5 in different aggregates, in accordance with former visual and photographic results, with an average ofp = 5 for sporadic meteors (Mclntosh, p. 343; Elford, p. 352; ~imek and Mclntosh, p. 362). There is definite variation of this exponent over the celestial sphere and with the time of the year (Belkovi~ and Pupy~ev, p. 373). Meteors of a stream are not appearing in groups but enter individually in a random fashion (V. Porub~n, p. 405). Among minor meteor streams, there is a possible family of 7 orbits associated with Comet Lexell 1770 I (A. K. Terent'eva, p. 408). Visual observations are still of great value, as shown during the 1966 Leonid Shower event, successfully observed in the U.S.S.R. and the U.S.A. (V. A. Bron~ten, p. 440). The path of the Earth through the shower was found to be only 90,000 km. A full historical review of the activity of the Leonid Shower since 1787 is given by Kazimir~ak-Polonskaja et al. (p. 449). A short but significant review of the Origins of Meteoritic Material is offered by F. L. Whipple (p. 481). From a collisional model of successive fragmentation of asteroids, J. S. Dohnanyi (p. 486) derives a theroretical equilibrium value for the 'population index' of the frequency of radii, p -- 1 = 1'837, in close agreement with an observed value of 1"80 -4- 0.04. As a guide to the trends of modern meteor research, this Symposium volume is indispensable to every worker in the field. E. J. OPIK
K. O. KIEPENIaEtr~R (Editor): Structure and Development of Solar Active Regions. Proceedings of the International Astronomical Union Symposium No. 35. Reidel, DordrechtHolland, 1968. xvii + 608 pp. $28.00. Tais book contains the complete proceedings of a symposium which was arranged by the International Astronomical Union and took place in Budapest, Hungary on 3-9 September 1967. The principal aim of the symposium was to review our current knowledge of the various phenomena associated with solar active regions and to improve our understanding of the relevant physical processes. Most of the 87 papers contained in the symposium proceedings are concerned with observations made by various techniques including radio, optical, ultraviolet and X-ray methods, which describe the magnetic and physical structures associated with an active region. The relationship between sunspots, faculae, plages, flares, prominences, and the underlying magnetic field phenomena is the main theme in these papers. The theoretical aspects are discussed in 8 papers which are concerned with the plasma physics problems associated with the development of an active region. A useful summary of the symposium is contained in the final review paper by Dr. C. De Jaeger. This paper discusses the structure and development of a solar active region in terms of most recent observations and theory, and also indicates the many areas where further work is required if the underlying physical processes are to be understood. The book is extremely well edited and presented and the quality of the diagrams and plates is excellent. Most papers are followed by the discussion as recorded at the symposium. The titles and authors of papers are listed in eight broad subject categories at the start of the book but there is no subject index to facilitate rapid reference to a specific topic. As a comprehensive review of present-day knowledge of the physics of solar active regions, this book will be a valuable addition to any library concerned with solar physics. W. M. BOY,TON
BOOK REVIEWS
L. KRES,~Cand F. M. MILt.t~N (Editors) : Physics and Dynamics of Meteors, LA.U. Symposium No. 33. Reidel, Dordrecht-Holland, 1968. xiii + 525 pp. 90 fls. Tim SYMPOSIUM,held in September 1967 at Tatranska Lomnica, Czechoslovakia, reflects the enormous shift of the meteor observational work into the realm of radar, the formerly dominant visual and photographic methods now acquiring but an auxiliary significance. The rapidly developing physical and dynamical theory supplements and interprets the factual material. Geographically, there is also a conspicuous shift--to the East, only partly due to the choice of the host country. Of the 50 papers, 14 belong to Czechoslovakia, 14 to Russia, 8 to the United States, 5 to Canada, 3 to England, 2 to Italy, and one each to Australia, East Germany, Japan and Sweden. The papers represent a fair cross section of current meteor research, from interplanetary dust to 'ordinary' meteors in the gram range of mass. Meteorites and cratering are not included. Most papers are well presented, often containing basic new material, with Abstracts and proper definitions of the terminology. However, some of the contributions are erring in this respect, thus unnecessarily impeding the reading. Introduced by 9 survey papers, the contributions are concerned with the derivation of the distribution of the masses, chemical composition, velocities, orbital elements and their changes, separately in different size classes of the meteors. They also deal with physical processes of meteor flight through the atmosphere. A few of the conclusions may be mentioned---as a sample of the contents. From 3200 radar records with the oblique-scattering method (Andrianov et al., p. 14), seasonal distributions of meteor flux over the celestrial sphere reduced to a constant limiting mass, as well as the distribution of velocities are derived. Meteor radar observations point to a variation of atmospheric density at 90--110 km level with the solar cycle, with density maximum at solar mininaum; the variation is opposite in phase to that of the uppermost atmosphere as deduced from satellite drag 03. A. Lindblad, p. 50). At Tokyo Astronomical Observatory, since 1963 a total of 79 meteor spectra have been obtained, of these 10 for sporadic meteors. A Leonld spectrum showed 73 identified lines including the forbidden oxygen 5577 A (Hi.rose et aL, p. 105). Telescopic meteors despite their smallness penetrate deeper into the atmosphere than the visual dustballs, reaching an endpoint at 81 km (Kohoutek, p. 143). This confirms former observations and seems to imply that they are compact grains not dustballs., Diffusion of ionized meteor trains can be inhibited by the Earth's magnetic field only ff the angle is less than 1° with the field direction (T. R. Kaiser, p. 161). From radar echo duration of night and daytime meteors, negative ion attachment rates are estimated and dissociative attachment to ozone (08 + e -* O- + Oi) is suggested (P. Gl6de, p. 175). Statistics of radar meteor orbits, based on 2500 orbits obtained at Jodrell Bank and 12500 orbits from Kharkov, U.S.S.R. (V. N. Lebedine~, p. 241), as compared with the more massive photographic meteors, reveals remarkable differences. At a mass limit of 0.001 g, the orbital inclinations are more nearly random, with many around 90 ° and retrograde (90-180°), while the more massive meteors show low inclinations and few retrograde orbits. Fireballs from the Prairie Network seem to point to a low average density of 0.4 g/cm 8 for the meteoroids, more or less the same as for dusthalls (R. E. McCrosky, p. 265), The difference, however, is in fragmentation and the conclusion may need revision because of the complexity of the ablation and deceleration phenomena in the deeper atmosphere. The micrometeorite flux in the neighbourhood of the Earth may be lower by some three orders of magnitude than recent acoustic sensor data have indicated (Nilsson and Southworth, p. 280); the so-called 'dust belt' may be non-existent. Theoretical models are proposed for the distribution of sporadic streaming of 1500 radar echoes over the celestial sphere (Carrara et al., p. 288). From the 13th century Chinese Encyclopaedia of Ma Touan-lin and other sources, published by E. Biot in 1848, fireball radiants have been deduced (Astapovi~ and Terent'eva, p. 308) which help to follow up the history of past meteor showers. The Perseids have appeared in 830 A.D. with a radiant displaced 20° from its present position. The Leonids have been there for all the time of the Chinese records. In all, seven of the present great showers were identified plus some 80 more or less certain radiants of minor showers. A thorough review of The Interplanetary Dust Cloud is presented by T. R. Kaiser (p. 325). 1435
1436
BOOK REVIEWS
A number of papers is devoted to the derivation of the meteor mass distrubution, represented as a power law. In the form R-,dR of the frequency of radii, the radar data point top from 2.5 to 5"5 in different aggregates, in accordance with former visual and photographic results, with an average ofp = 5 for sporadic meteors (Mclntosh, p. 343; Elford, p. 352; ~imek and Mclntosh, p. 362). There is definite variation of this exponent over the celestial sphere and with the time of the year (Belkovi~ and Pupy~ev, p. 373). Meteors of a stream are not appearing in groups but enter individually in a random fashion (V. Porub~n, p. 405). Among minor meteor streams, there is a possible family of 7 orbits associated with Comet Lexell 1770 I (A. K. Terent'eva, p. 408). Visual observations are still of great value, as shown during the 1966 Leonid Shower event, successfully observed in the U.S.S.R. and the U.S.A. (V. A. Bron~ten, p. 440). The path of the Earth through the shower was found to be only 90,000 km. A full historical review of the activity of the Leonid Shower since 1787 is given by Kazimir~ak-Polonskaja et al. (p. 449). A short but significant review of the Origins of Meteoritic Material is offered by F. L. Whipple (p. 481). From a collisional model of successive fragmentation of asteroids, J. S. Dohnanyi (p. 486) derives a theroretical equilibrium value for the 'population index' of the frequency of radii, p -- 1 = 1'837, in close agreement with an observed value of 1"80 -4- 0.04. As a guide to the trends of modern meteor research, this Symposium volume is indispensable to every worker in the field. E. J. OPIK
K. O. KIEPENIaEtr~R (Editor): Structure and Development of Solar Active Regions. Proceedings of the International Astronomical Union Symposium No. 35. Reidel, DordrechtHolland, 1968. xvii + 608 pp. $28.00. Tais book contains the complete proceedings of a symposium which was arranged by the International Astronomical Union and took place in Budapest, Hungary on 3-9 September 1967. The principal aim of the symposium was to review our current knowledge of the various phenomena associated with solar active regions and to improve our understanding of the relevant physical processes. Most of the 87 papers contained in the symposium proceedings are concerned with observations made by various techniques including radio, optical, ultraviolet and X-ray methods, which describe the magnetic and physical structures associated with an active region. The relationship between sunspots, faculae, plages, flares, prominences, and the underlying magnetic field phenomena is the main theme in these papers. The theoretical aspects are discussed in 8 papers which are concerned with the plasma physics problems associated with the development of an active region. A useful summary of the symposium is contained in the final review paper by Dr. C. De Jaeger. This paper discusses the structure and development of a solar active region in terms of most recent observations and theory, and also indicates the many areas where further work is required if the underlying physical processes are to be understood. The book is extremely well edited and presented and the quality of the diagrams and plates is excellent. Most papers are followed by the discussion as recorded at the symposium. The titles and authors of papers are listed in eight broad subject categories at the start of the book but there is no subject index to facilitate rapid reference to a specific topic. As a comprehensive review of present-day knowledge of the physics of solar active regions, this book will be a valuable addition to any library concerned with solar physics. W. M. BOY,TON