Showing papers in "Space Science Reviews in 1976"
TL;DR: In this paper, a new auroral pattern, which indicates major auroral characteristics in all local time sectors, is presented, as a result of extensive study of DMSP-8531 and -10533 auroral photographs.
Abstract: A new auroral pattern, which indicates major auroral characteristics in all local time sectors, is presented. It has emerged as a result of extensive study of DMSP-8531 and -10533 auroral photographs. The paper presents also a brief summary of recent studies on the role of the north-south component of the interplanetary magnetic field on large-scale auroral dynamics and on the relationship between substorm energy and the size of the oval.
117 citations
TL;DR: In this article, an attempt has been made to describe the large variety of geomagnetic variations, both regular and irregular, both with a brief description of the Earth and its environment, different types of quiet-day variations are described and present ideas regarding their possible mechanisms.
Abstract: In this review, an attempt has been made to describe the large variety of geomagnetic variations, both regular and irregular. After a brief description of the Earth and its environment, different types of quiet-day variations are described and present ideas regarding their possible mechanisms are discussed. In general, periodicities exceeding several tens of years can be attributed to changes in the interior of the Earth while periodicities of 22 years or less seem to be related to phenomena connected with the Sun, through the interaction of solar wind with the Earth's magnetosphere. The morphology of irregular storm-time variations and its relationship with interplanetary plasma parameters is discussed with particular reference to the orientations of interplanetary magnetic field, particularly the southward B
z
component which seems to play a crucial role. Various storm-time phenomena occurring in the polar, auroral, mid-latitude and equatorial regions and their interconnections are described. Theoretical models offering explanations of many of these phenomena are discussed, the unsolved problems are outlined, and the direction of the present effort in solving these is indicated.
78 citations
TL;DR: In this paper, a review of the available observations and the present state of knowledge of the long-term modulation of the intensity of galactic cosmic rays is presented, which occurs in response to the 11-year cycle of solar activity.
Abstract: This paper reviews the available observations and the present state of knowledge of the long-term modulation of the intensity of galactic cosmic rays. This modulation occurs in response to the 11-year cycle of solar activity. The propagation of solar cosmic rays, as well as short-term modulation changes, are not explicitly discussed. The main theme of the paper is to interpret the observations in terms of the existing modulation theories. The theoretical model describes the propagation of cosmic rays in the interplanetary medium in terms of diffusion, convection, and energy changes. The topic is introduced with a brief description of how the cosmic-ray diffusion tensor is calculated from the fluctuations in the interplanetary magnetic field (Section 2). The cosmic-ray transport equations are discussed in Section 3. Observations of cosmic-ray intensity spectra, density gradients and anisotropies, and the evolution of the 11-year modulation cycle, are described in Sections 4, 5, and 6 respectively. It is shown that the principles of the modulation are understood in terms of the theoretical models. However, measurements of low-energy cosmic rays (kinetic energies ≲ 50 MeV nucleon−1) during the last few years, indicate that the models may be incomplete. On the other hand, it is also pointed out that the available observations are not always sufficient to evaluate the full consequences of the theoretical models. In particular, we need observations out of the ecliptic plane, as well as an increased effort to measure the density gradients and anisotropies at a single position (e.g. Earth) and as function of time.
75 citations
55 citations
TL;DR: In this paper, the positions of the magnetopause and bow shock suffered significant variations during the period of unusual solar activity in August 1972, and an attempt was made to identify the structure according to near-Earth observations.
Abstract: Experimental data of Prognoz, Prognoz-2 and HEOS-2 on interplanetary plasma and magnetosheath plasma in the period of unusual solar activity in August 1972 are considered. All measurements showed the extremal plasma properties with strong variations. Attempt is made to identify the structure according to near-Earth observations. The positions of the magnetopause and bow shock suffered significant variations during this time interval.
52 citations
TL;DR: In this article, solar-wind observations associated with the enhanced levels of solar activity in August 1972 are reviewed with emphasis on recent analyses which more unambiguously characterize the changes in the interplanetary medium.
Abstract: Solar-wind observations associated with the enhanced levels of solar activity in August 1972 are reviewed with emphasis on recent analyses which more unambiguously characterize the changes in the interplanetary medium. Observations from Pioneer 9 at about 0.8 AU, Pioneer 10 at 2.2 AU, and in the vicinity of earth are reviewed and reinterpreted in the light of new data. Recent calculations of local shock velocities are reviewed, and their implications are discussed. These results indicate that, contrary to previously published observations, there is no significant deceleration of the interplanetary shocks between 0.8 AU and 2.2 AU.
38 citations
TL;DR: The overall view of Mars has changed from earthlike in the prespacecraft era to moon-like following the flyby missions and finally to a planet with intermediate characteristics as mentioned in this paper.
Abstract: The overall view of Mars has changed from earthlike in the prespacecraft era to moonlike following the flyby missions and finally to a planet with intermediate characteristics. There are many impact craters as on the moon, but tectonic and volcanic features resembling structures on earth are also present. However, there is a lack of evidence for the compressional deformation associated with terrestrial plate tectonics and continental drift. Current analyses indicate that Mars has a differentiated interior with a crust and mantle and perhaps a core. Whenever the nature of interior processes, whether overall mantle expansion, plumes, or full-scale convection, the effects at the surface have been predominantly vertical with formation of broad regions of uplift and depression. One of the results is hemispheric asymmetry with cratered terrain in the south and younger uncratered plains in the north.
37 citations
TL;DR: In this article, a review of interplanetary-magnetic field measurements made by Pioneer 9 and 10, HEOS 2, and Explorer 41 during early August 1972 is presented.
Abstract: Interplanetary-magnetic-field measurements made by Pioneers 9 and 10, HEOS 2, and Explorer 41 during early August 1972 are reviewed. It is noted that the two Pioneers were nearly radially aligned during the flare events, with Pioneer 9 at a distance of 0.78 AU from the sun and Pioneer 10 at a distance of 2.2 AU. The data obtained by Pioneer 9, Pioneer 10, and the two near-earth satellites are analyzed separately, and the major flare-associated shocks are identified. An attempt is made to identify corresponding shocks at the different locations and to determine their propagation velocities in the region between 0.8 and 2.2 AU. It is found that there was an obvious tendency for the average shock velocities to decrease with increasing radial distance from the sun and that the local velocities at the Pioneer locations were significantly smaller than the appropriate average values. A comparison of these local velocities indicates that there was a large deceleration of the shocks between the sun and some distance within 0.8 AU but little, if any, deceleration beyond that distance. A plot of average shock velocities from the sun to 1.0 AU as a function of longitude separation between the flares and Pioneer 9 is shown to suggest a pronounced deviation of the shock fronts from spherical symmetry.
36 citations
TL;DR: In this paper, the authors reviewed the observations of interplanetary scintillation of radio sources in early August 1972 and found that the enhancements in solar wind speed and SCI associated with three shock waves were detected, the extent in both longitude and latitude of the shock wave associated with the solar flare on 7 August, the anisotropic expansion of shock waves and the detection of the corotating high-speed streams are main results deduced from the observations.
Abstract: The observations of interplanetary scintillation of radio sources in early August 1972 are reviewed. Three-site measurements of solar wind speed were made at University of California, San Diego (73.8 MHz) and at Nagoya University, Toyokawa (69.3 MHz). Single-site measurements of scintillation index were made at Mullard Radio Astronomy Observatory, Cambridge (81.5 MHz) and at University of Adelaide (111.5 MHz). The enhancements in solar wind speed and scintillation index associated with three shock waves were detected. The extent in both longitude and latitude of the shock wave associated with the solar flare on 7 August, the anisotropic expansion of shock waves and the detection of the corotating high-speed streams are main results deduced from the observations.
21 citations
TL;DR: The solar/interplanetary events in early August 1972 are summarized in Section 1 (Introduction), Section 2 (August 1972 Events in the Solar Cycle 20), Section 3 (Evolution of Solar Active Region: McMath region No. 11976 and its flare-activity), Section 4 (Radio, X-ray, and Proton Characteristics of Four Major Solar Flares: F-1 at 0316 UT on 2 August, F-2 at 1958 UT and F-4 at 1522 UT on 7 August), Section 5 (Interplanetary Shock Waves: observations of
Abstract: The solar/interplanetary events in early August 1972 are summarized in Section 1 (Introduction), Section 2 (August 1972 Events in the Solar Cycle 20), Section 3 (Evolution of Solar Active Region: McMath region No. 11976 and its flare-activity), Section 4 (Radio, X-ray, and Proton Characteristics of Four Major Solar Flares: F-1 at 0316 UT on 2 August, F-2 at 1958 UT on 2 August, F-3 at 0626 UT on 4 August, and F-4 at 1522 UT on 7 August), Section 5 (Interplanetary Shock Waves: observations of the shock waves generated from the four major solar flares at several points in interplanetary space, the Earth, Pioneer-9, Pioneer-10, etc.; interplanetary scintillations; shock trajectories in the heliosphere), Section 6 (Variations of Solar and Galactic Cosmic Rays: four solar proton events observed in the vicinity of the earth and at the Pioneer-9 location in the course of interplanetary disturbances; Forbush decreases of cosmic ray intensity; the spikeshaped variation in solar and galactic cosmic rays on 5 August), and Section 7 (Conclusions).
17 citations
TL;DR: In this paper, various reports of ionospheric responses during the August 1972 storm events are reviewed with respect to the phenomena in three major world sectors, N-S America, Afro-Europe, and Austro-Asia, in order to have a global picture.
Abstract: Various reports of ionospheric responses during the August 1972 storm events are reviewed with respect to the phenomena in three major world sectors, N-S America, Afro-Europe, and Austro-Asia, in order to have a global picture. Emphasized highlights are (1) extensive investigation of the sudden increase of the total electron content estimated from Faraday-rotation measurements of satellite signals; (2) a dramatic upward surge above 300 km altitude, soon after a flare, measured by the Millstone Hill incoherent scatter radar; (3) electron density profiles, electric fields and conductivities, and neutral winds, at the time of the geomagnetic storm sudden commencement and during the succeeding storms, measured by the Chatanika incoherent scatter radar; and, (4) approximately 2.5-h oscillatory F2 density variations in Eastern Asia during the F2 storm main phase. To show temporal variations of the latitudinal distributions of storm-time F2 electron densities, in three longitudinal sectors separated about 60° longitude each, newly investigated results of the F2 hourly data at 35 stations in the Asia-Australia-Pacific sector are then exhibited. Finally, current theories or at least theoretical ideas of ionospheric storm mechanisms are briefly introduced, and a few remarks on the August events in the light of those theories are presented.
TL;DR: In this paper, a detailed analysis of low energy cosmic rays produced by the spectacular series of solar flares in August 1972 are reviewed, and the proton differential energy spectrum is discussed at certain key times during the events.
Abstract: Low energy cosmic rays produced by the spectacular series of solar flares in August 1972 are reviewed. Satellite observations of electrons, protons and alpha particles are compared. The proton differential energy spectrum is discussed at certain key times during the events. Three energetic storm particle events were produced over the time period covered by the detailed analysis, 2–11 August. The origin of the cosmic ray square wave on 5 August is discussed. Measurements of heavy ions are available both from Pioneer 10 and from a high latitude rocket flight on 4 August.
TL;DR: A series of spectacular cosmic ray events which included two relativistic solar particle enhancements and three major Forbush decreases were registered by ground-based cosmic ray monitoring stations beginning 4 August, 1972 as mentioned in this paper.
Abstract: A series of spectacular cosmic ray events which included two relativistic solar particle enhancements and three major Forbush decreases were registered by ground-based cosmic ray monitoring stations beginning 4 August, 1972. These were associated with four major proton flare events on the Sun and with large interplanetary magnetic field disturbances and high velocity shock waves. This review attempts to discuss and interpret the high energy cosmic ray phenomena observed during this period in the light of the known behaviour of low energy particulate flux, interplanetary plasma and field observations and other associated solar and terrestrial effects recorded during this period.
TL;DR: In this paper, a review of the direction-finding capability of the IMP-6 satellite during the period of high solar activity in August 1972 is presented. And the problem of assigning an electron-density scale and its influence on determining burst trajectories is reviewed.
Abstract: Type II, type III, and continuum solar radio events, as well as intense terrestrial magnetospheric radio emissions, were observed at low frequencies (10 MHz to 30 kHz) by the IMP-6 satellite during the period of high solar activity in August 1972. This review covers briefly the unique direction-finding capability of the experiment, a detailed chronology of the low-frequency radio events, and, where possible, their association with both ground-based radio observations and solar flares. The attempted observation of solar bursts in the presence of intense magnetospheric noise may, as illustrated, lead to erroneous results in the absence of directional information. The problem of assigning an electron-density scale and its influence on determining burst trajectories is reviewed. However, for the disturbed conditions existing during the period in question, it is felt that such trajectories cannot be determined accurately by this method. The capabilities, limitations, and observing programs of present and future satellite experiments are briefly discussed.
TL;DR: In this paper, the authors reviewed the optical observations and analyses of the flares of August 1972 with emphasis on their dynamics, including the storage and release of magnetic energy, triggering mechanisms, particle acceleration and magnetic field reconnection and coronal and solar wind responses.
Abstract: The optical observations and analyses of the flares of August 1972 are reviewed with emphasis on their dynamics. In particular, various assessments are made of possible quantitative interpretation of observed data. Specific topics considered are the storage and release of magnetic energy, triggering mechanisms, particle acceleration and magnetic field reconnection, and coronal and solar wind responses. Supplemental discussions on possible future direction of research are presented, illustrating the need for examination of the storage and release of flare energy in the lower solar atmosphere.
TL;DR: In this article, the brightness behavior of comets and the general level of solar activity in the eleven-year cycle appear to be statistically related, and the responses of individual comets to solar events are not sufficiently well calibrated to permit using them as reliable interplanetary probes.
Abstract: Evidence for correlations of brightness fluctuations of heads of comets with solar and solar-related phenomena is presented, and the examples of Comet Schwassmann-Wachmann (1) and Giacobini-Zinner in 1959 and 1972 are examined. Brightness behavior of comets and the general level of solar activity in the eleven-year cycle appear to be statistically related. At present the responses of individual comets to solar events are not sufficiently well calibrated to permit using them as reliable interplanetary probes.
TL;DR: The solar wind velocity and interplanetary magnetic field were unusually high late on 4 August and early on 5 August, 1972 as discussed by the authors, and the magnetosheath field near noon was several hundred gammas and frequently south during these intervals.
Abstract: The solar wind velocity and interplanetary magnetic field were unusually high late on 4 August and early on 5 August, 1972. The magnetopause was close to or below 6.6 R
e from 2117 to 2318 UT and close to or below 5.1 R
e from 2236 to 2318 UT on 4 August. The magnetosheath field near noon was several hundred gammas and frequently south during these intervals, and there was some evidence of field erosion. The entry of solar wind plasma into the inner magnetosphere during this period was not unusually high, however. Proton energy density was lower than in the storms of December 1971, and June 1972. The plasmapause steadily moved inward on 4 and 5 August; it reached 2 R
e before expanding on 6 August. The unusually high amplitude magnetic pulsations commenced near 2240 UT, 4 August, and lasted until near noon on 5 August. Both the close magnetopause and the large pulsations appear to be due to the high solar wind velocity following the shock that reached Earth at 2054 UT on 4 August.
TL;DR: In this paper, ground-based observations of the variable solar radio emission ranging from few millimetres to decametres have been used as a diagnostic tool to gain coherent phenomenological understanding of the great 2, 4 and 7 August, 1972 solar events in terms of dominant physical processes like generation and propagation of shock waves in the solar atmosphere, particle acceleration and trapping.
Abstract: Ground-based observations of the variable solar radio emission ranging from few millimetres to decametres have been used here as a diagnostic tool to gain coherent phenomenological understanding of the great 2, 4 and 7 August, 1972 solar events in terms of dominant physical processes like generation and propagation of shock waves in the solar atmosphere, particle acceleration and trapping. The basic data used in this review have been collected by many workers throughout the world utilizing a variety of instruments such as fixed frequency radiometers, multi-element interferometers, dynamic spectrum analysers and polarimeters. Four major flares are selected for detailed analysis on the basis of their ability to produce energetic protons, shock waves, polar cap absorptions (PCA) and sudden commencement (SC) geomagnetic storms. A comparative study of their radio characteristics is made. Evidence is seen for the pulsations during microwave bursts by the mechanism similar to that proposed by McLean et al. (1971), to explain the pulsations in the metre wavelength continuum radiation. It is suggested that the multiple peaks observed in some microwave bursts may be attributable to individual flares occurring sequentially due to a single initiating flare. Attempts have been made to establish identification of Type II bursts with the interplanetary shock waves and SC geomagnetic storms. Furthermore, it is suggested that it is the mass behind the shock front which is the deciding factor for the detection of shock waves in the interplanetary space. It appears to us that more work is necessary in order to identify which of the three moving Type IV bursts (Wild and Smerd, 1972), namely, advancing shock front, expanding magnetic arch and ejected plasma blob serves as the piston-driver behind the interplanetary shocks. The existing criteria for proton flare prediction have been summarized and two new criteria have been proposed. Observational limitations of the current ground-based experimental techniques have been pointed out and a suggestion has been made to evolve appropriate observational facilities for solar work before the next Solar Maximum Year (SMY).
TL;DR: In this article, the authors trace the evolution of stellar models from walled, thermodynamic-equilibrium models to de-isolated models featuring transition zones and nonlocal thermodynamic equilibrium.
Abstract: The purpose of the paper is to show how the solar-stellar symbiotic approach has led to the modeling of a star as a concentration of matter and energy. By 'solar-stellar symbiosis' is meant the philosophy of investigation according to which one asks what change in our general understanding of stellar structure and of stellar spectroscopic diagnostics is required to satisfy both the sun and an unusual star when, for example, some feature of an unusual star is discovered. The evolution of stellar models is traced, from walled, thermodynamic-equilibrium models to de-isolated models featuring transition zones and nonlocal thermodynamic equilibrium.
TL;DR: In this article, the United Nations Outer Space Treaty, its implications, and the other Treaties derived from it and established subsequently are described, together with the legal problems with regard to Earth surveying and of those related to direct broadcasting satellites.
Abstract: A review is given of the main elements of space law. We describe the various international organizations on space law, and particularly the history and structure of the United Nations Committee on the Peaceful Uses of Outer Space and its subcommittees. Thereafter we describe the United Nations Outer Space Treaty, its implications, and the other Treaties derived from it and established subsequently. Finally a description is given of the legal problems with regard to Earth surveying, and of those related to direct broadcasting satellites.