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Galactic dynamo generated magnetic field periodic modes based on mathematical model involving cyclonic turbulence and nonuniform rotation of gaseous disk
Solar and lunar hydromagnetic tides in earth magnetosphere obtained from electrostatic fields in dynamo region
Milky Way galaxy poloidal magnetic field generation with hydromagnetic dynamos, showing galactic cosmic rays as major driving force
Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.
The effect of the coriolis force was examined for stability of rotating hydromagnetic systems. It is shown that the effect of this force is to inhibit the onset of instability which leads to convective motion in these systems. The possibility of the existence of a dynamo process in Jupiter's interior is discussed, taking into account the effect of the coriolis force.
It is shown that the moon possesses an extraordinary response to induction from the solar wind due to a combination of a high interior electrical conductivity together with a relatively resistive crustal layer into which the solar wind dynamic pressure forces back the induced field. The dark side response, devoid of solar wind pressure, is approximately that expected for the vacuum case. These data permit an assessment of the interior conductivity and an estimate of the thermal gradient in the crustal region. The discovery of a large permanent magnetic field at the Apollo 12 site corresponds approximately to the paleomagnetic residues discovered in both Apollo 11 and 12 rock samples. The implications regarding an early lunar magnetic field are discussed and it is shown that among the various conjectures regarding the early field the most prominent are either an interior dynamo or an early approach to the earth though no extant model is free of difficulties.
The remanent magnetization of samples returned from the moon by the Apollo 11 and 12 missions consists, in most cases, of two distinct components. An unstable component is readily removed upon alternating field (AF) demagnetization in fields less than 100 Oe and is considered to be an isothermal remanence acquired during or after return to earth. The second component is unaltered by demagnetization in fields up to 400 Oe. It is probably a thermoremanent magnetization due to cooling from above 800 C in the presence of a field of a few thousand gammas. Chips from individual rocks have the same direction of magnetization after demagnetization, while the directions of different samples are random. This again demonstrates the high stability. Our data imply that the moon experienced a magnetic field that lasted at least from about 3.0 to 3.8 b.y., which is the age of Apollo 11 and 12 samples. One explanation of the origin of this field is that the moon had a liquid core and a self-exciting dynamo early in its history.
A study of stellar chromospheres based on the internal structure of particular stars is presented. Used are complex flow diagrams of the linkage paths between mass loss, angular momentum loss, magnetic field from the turbulent dynamo and its relations to differential rotations and the convection zone, and stellar evolution.
The Apollo 16 lunar surface magnetometer (LSM) activation completed the network installation of magnetic observatories on the lunar surface and initiated simultaneous measurements of the global response of the moon to large-scale solar and terrestrial magnetic fields. Fossil remanent magnetic fields have been measured at nine locations on the lunar surface, including the Apollo 16 LSM site in the Descartes highlands area. This fossil record indicates the possible existence of an ancient lunar dynamo or a solar or terrestrial field much stronger than exists at present. The experimental technique and operation of the LSM are described and the results obtained are discussed.
It has been proposed that lunar samples were magnetized by a field created by a lunar core of molten Fe. Low abundances of siderophile elements in lunar rocks are compatible with formation of a metallic lunar core. A molten Fe core requires that the bulk of the moon was above, or close to, the melting point, a requirement which disagrees with most models of the lunar thermal regime. A core (or perhaps a layer or pockets) of molten Fe-Ni-S, at or close to the eutectic composition would act as a lunar dynamo, and be at a temperature (approximately 1000 C) consistent with some reasonable models of lunar thermal history. The existence of a Fe-Ni-S core would also partly explain the depletion in volatile elements in lunar basalts. Such a core, occupying up to 20% of the moon's radius, requires a bulk S content for the moon of only 0.3 wt %.
The work is concerned with solar influences on the earth's upper atmosphere and electromagnetic environment partly through solar ultraviolet and X rays, but particularly through corpuscular radiations. The sun and interplanetary space, the internal structure and magnetic field of the earth, the terrestrial atmosphere and photochemistry, and the dynamics of the upper atmosphere and dynamo action are considered. The formation of the magnetosphere, energetic particles, plasma, and electromagnetic waves in the magnetosphere, solar storms and their extension into interplanetary space, and magnetospheric storms are treated.
The currently known astronomical, chemical, and magnetic data are not uniquely indicative of an extensively and globally molten moon. It is argued that an accretional layering occurred in the moon, but at temperatures below solidus. The excess mass in the near side of the moon compatible with a 2-km displacement in the center of mass relative to the center of figure and the moment of inertia data is considered to be due to Fe-FeS liquid formation and inhomogeneous segregation. These Fe-FeS bodies, termed 'fescons,' are shown to be capable of accounting for the presently available magnetization data, by acting as small regenerative dynamos with a time-stability less than that of the terrestrial equivalent. The chemical characteristics of the highly differentiated materials, are considered to be due to small-scale localized melting caused by collisional events, from sources in which accessory phases play a significant role. Mare basalts are considered to be melts in the overlying material produced at a later time by K-40 radioactivity in the fescons. Some consequences of the present hypothesis are suggested. It is concluded that these and other characteristics of the lunar materials are reconcilable with a 'cold' moon, such as discussed by Urey over the past two decades.
Turbulent diffusion of magnetic field plays an essential role in the generation of magnetic field in most astrophysical bodies. Review of what can be proved and what can be believed about the turbulent diffusion of magnetic field. Observations indicate the dissipation of magnetic field at rates that can be understood only in terms of turbulent diffusion. Theory shows that a large-scale weak magnetic field diffuses in a turbulent flow in the same way that smoke is mixed throughout the fluid by the turbulence. The small-scale fields (produced from the large-scale field by the turbulence) are limited in their growth by reconnection of field lines at neutral points, so that the turbulent mixing of field and fluid is not halted by them. Altogether, it appears that the mixing of field and fluid in the observed turbulent motions in the sun and in the Galaxy is unavoidable. Turbulent diffusion causes decay of the general solar fields in a decade or so, and of the galactic field in 100 m.y. to 1 b.y. It is concluded that continual dynamo action is implied by the observed existence of the fields.
The current state of the theory of Jupiter's outer atmosphere is briefly reviewed. The similarities and dissimilarities between the terrestrial and Jovian upper atmospheres are discussed, including the interaction of the solar wind with the planetary magnetic fields. Estimates of Jovian parameters are given, including magnetosphere and auroral zone sizes, ionospheric conductivity, energy inputs, and solar wind parameters at Jupiter. The influence of the large centrifugal force on the cold plasma distribution is considered. The Jovian Van Allen belt is attributed to solar wind particles diffused in toward the planet by dynamo electric fields from ionospheric neutral winds, and the consequences of this theory are indicated.
It is shown how the usual nearly-free-electron model for the electrical resistivity of simple liquid metals can be extended to the case of liquid transition metals such as iron. A simple prescription is given for calculating the resistivity at different densities and temperatures. As an application and example of the method, calculations on liquid iron at different densities were carried out and the resistivity of molten iron in the earth's outer core is estimated. The effects of alloying iron with other elements are also considered. The calculated conductivity of the outer core is well within the limit required for the dynamo model of the geomagnetic field and agrees well with some recent shock wave data.
All lunar samples measured to date contain a weak but stable remanent magnetization of lunar origin. The magnetization is carried by metallic iron and is considered to be caused by cooling from above the Curie point in the presence of a magnetic field. Although at present the moon does not have a global field, the remanent magnetization of the rock samples and the presence of magnetic anomalies, both on the near and far side of the moon, imply that the moon experienced a magnetic field during some portion of its history. The field could have been generated in a liquid iron core sustaining a self-exciting dynamo, but there are some basic thermal and geochemical objections that need to be resolved.
Reviews of the evidence for magnetization of the moon found from discovery of remanence in lunar samples, direct measurements of fields on the surface of the moon, and direct and indirect determination of fields from lunar orbit. It is shown that the evidence implies that the fields are not only local but that regional properties are found though there is still no direct evidence for a global dipole moment. Limits on the detectibility of a global dipole are given and it is shown that the strength of magnetization for reasonable thermal gradients places possible dipole moments just below the threshold of detectibility of current experiments. The hypothesis of plate magnetics is reviewed. Current ideas regarding the source of the background magnetic field presumed responsible for the magnetization are critically considered. These are the dynamo hypothesis and primordial magnetization. Consequences of both are discussed and finally the constraints placed upon the thermal evolution of the moon are considered.
The results of a theoretical study of the radiation belts of Jupiter are presented. The model of the electron radiation belt is based on the assumption that electrons from the solar wind are transported into the region near Jupiter by radial diffusion. The diffusion is driven by electric fields caused by an upper atmospheric dynamo in Jupiter's ionosphere. A proton radiation belt at Jupiter is predicted.