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Dyal, P.

Publications and source records attributed to Dyal, P..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Global electromagnetic induction in the moon and planets

Experiments and analyses concerning electromagnetic induction in the moon and other extraterrestrial bodies are summarized. The theory of classical electromagnetic induction in a sphere is first considered, and this treatment is extended to the case of the moon, where poloidal eddy-current response has been found experimentally to dominate other induction modes. Analysis of lunar poloidal induction yields lunar internal electrical conductivity and temperature profiles. Two poloidal-induction analytical techniques are discussed: a transient-response method applied to time-series magnetometer data, and a harmonic-analysis method applied to data numerically Fourier-transformed to the frequency domain, with emphasis on the former technique. Attention is given to complicating effects of the solar wind interaction with both induced poloidal fields and remanent steady fields. The static magnetization field induction mode is described, from which are calculated bulk magnetic permeability profiles. Magnetic field measurements obtained from the moon and from fly-bys of Venus and Mars are studied to determine the feasibility of extending theoretical and experimental induction techniques to other bodies in the solar system.

Dyal, P.↗
NASA NTRS1973

Iron abundance in the moon from magnetometer measurements

Apollo 12 and 15 lunar surface magnetometer data with simultaneous lunar orbiting Explorer 35 data are used to plot hysteresis curves for the whole moon. From these curves a whole-moon permeability mu = 1.029 + 0.024 or - 0.019 is calculated. This result implies that the moon is not composed entirely of paramagnetic material, but that ferromagnetic material such as free iron exists in sufficient amounts to dominate the bulk lunar susceptibility. From the magnetic data the ferromagnetic free iron abundance is calculated. Then for assumed compositional models of the moon the additional paramagnetic iron is determined, yielding total lunar iron content. The calculated abundances are as follows: ferromagnetic free iron = 5 + or - 4 wt. percent, and total iron in the moon = 9 + or - 4 wt. percent.

Parkin, C. W.↗
NASA NTRS1973

Surface magnetometer experiments: Internal lunar properties

Magnetic fields have been measured on the lunar surface at the Apollo 12, 14, 15, and 16 landing sites. The remanent field values at these sites are respectively 38 gammas, 103 gammas (maximum), 3 gammas, and 327 gammas. Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites are compressed and that the scale size of the Apollo 16 remanent field is 5 or = L 100 km. The global eddy current fields, induced by magnetic step transients in the solar wind, were analyzed to calculate an electrical conductivity profile. From nightside data it was found that deeper than 170 km into the moon, the conductivity rises from 0.0003 mhos/m to 0.01 mhos/m at 1000 km depth. Analysis of dayside transient data using a spherically symmetric two-layer model yields a homogeneous conducting core of radios 0.9 R and conductivity sigma = 0.001 mhos/m, surrounded by a nonconducting shell of thickness 0.1 R. This result is in agreement with a nonconducting profile determined from nightside data. The conductivity profile is used to calculate the temperature for an assumed lunar material of peridotite. In an outer layer the temperature rises to 850 to 1050 K, after which it gradually increases to 1200 to 1500 K at a depth of approximately 1000 km.

Dyal, P.↗
NASA NTRS1973

Surface magnetometer experiments - Internal lunar properties

Magnetic fields have been measured on the lunar surface at the Apollo 12, 14, 15, and 16 landing sites. The remanent field values at these sites are respectively 38, 103 (maximum), 3, and 327 gamma (maximum). Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites are compressed and that the scale size of the Apollo 16 remanent field is 5 less than or equal to L less than 100 km. The global eddy current fields, induced by magnetic step transients in the solar wind, have been analyzed to calculate an electrical conductivity profile. From nightside data it has been found that deeper than 170 km into the moon, the conductivity rises from .0003 mho/m to .01 mho/m at 1000 km depth. Analysis of dayside transient data using a spherically symmetric two-layer model yields a homogeneous conducting core with a radius equal to 0.9 lunar radius and a conductivity of .001 mho/m, surrounded by a nonconducting shell of thickness equal to 0.1 lunar radius.

Dyal, P.↗
NASA NTRS1973

Iron abundance in the moon from magnetometer measurements

Apollo 12 and 15 lunar surface magnetometer data with simultaneous lunar orbiting Explorer 35 data are used to plot hysteresis curves for the whole moon. From these curves a whole-moon permeability of 1.029 (+0.024 or -0.019) is calculated. This result implies that the moon is not composed entirely of paramagnetic material, but that ferromagnetic material such as free iron exists in sufficient amounts to dominate the bulk lunar susceptibility. From the magnetic data the ferromagnetic free iron abundance is calculated. Then for assumed compositional models of the moon the additional paramagnetic iron is determined, yielding total lunar iron content. The calculated abundances are as follows: ferromagnetic free iron, 5 plus or minus 4 wt %; total iron in the moon, 9 plus or minus 4 wt %.

Parkin, C. W.↗
NASA NTRS1972

Measurements of lunar magnetic field interaction with the solar wind.

Study of the compression of the remanent lunar magnetic field by the solar wind, based on measurements of remanent magnetic fields at four Apollo landing sites and of the solar wind at two of these sites. Available data show that the remanent magnetic field at the lunar surface is compressed as much as 40% above its initial value by the solar wind, but the total remanent magnetic pressure is less than the stagnation pressure by a factor of six, implying that a local shock is not formed.

Dyal, P.↗
NASA NTRS1972

Lunar properties from transient and steady magnetic field measurements.

The electrical conductivity of the lunar interior has been determined from magnetic field step transients measured on the lunar dark side. The simplest model which best fits the data is a spherically symmetric three layer model having a nonconducting outer crust, an intermediate layer with electrical conductivity of .00035 mhos/m, and an inner core with conductivity of .01 mhos/m. Temperatures calculated from these conductivities in the three regions for an example of an olivine moon are as follows: crust, below 440 K; intermediate layer, 890 K; and core, 1240 K. The whole-moon relative permeability has been calculated from the measurements to be 1.03 plus or minus 0.13.

Dyal, P.↗
NASA NTRS1972

Lunar surface magnetometer experiment

The Apollo 15 lunar-surface magnetometer (LSM) is one of a network of magnetometers that have been deployed on the moon to study intrinsic remanent magnetic fields and global magnetic response of the moon to large-scale solar and terrestrial magnetic fields. From these field measurements, properties of the lunar interior such as magnetic permeability, electrical conductivity, and temperature can be calculated. In addition, correlation with solar-wind-spectrometer data allows study of the the solar-wind plasma interaction with the moon and, in turn, investigation of the resulting absorption of gases and accretion of an ionosphere. These physical parameters and processes determined from magnetometer measurements must be accounted for by comprehensive theories of origin and evolution of the moon and solar system.

Dyal, P.↗
NASA NTRS1972

Lunar surface magnetometer experiment

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.

Dyal, P.↗
NASA NTRS1972

Lunar portable magnetometer experiment

The purpose of the Apollo 16 lunar portable magnetometer (LPM) experiment is to measure the permanent magnetic field at different geological sites on the lunar surface. The LPM field measurements are a vector sum of the steady remanent field from the lunar crust and of the time-varying ambient fields. The remanent magnetic fields measured in the Descartes region are the largest extraterrestrial fields yet measured in situ. These measurements show for the first time that the Descartes highlands have a stronger remanent magnetization than do the mare regions of the previous Apollo landing sites. The experimental technique used in the LPM experiment is described and the preliminary results obtained are discussed.

Dyal, P.↗
NASA NTRS1972

Surface magnetometer experiments - Internal lunar properties and lunar field interactions with the solar plasma.

The remanent magnetic fields measured to date on the moon are 38 plus or minus 3 gamma at Apollo 12 in Oceanus Procellarum; 103 plus or minus 5 and 43 plus or minus 6 gamma at two Apollo 14 sites separated by 1.1 km in Fra Mauro; and 6 plus or minus 4 gamma at the Apollo 15 Hadley-Apennines site. Measurements show that the 38-gamma remanent field at Apollo 12 is compressed to 54 gamma by a solar wind pressure increase of 7 x 10 to the minus 8th dyne/sq cm. The change in magnetic pressure is proportional to the change in plasma pressure, and the field is compressed primarily in the z (northerly) component. The electrical conductivity of the lunar interior has been determined from magnetic step transient measurements made on the lunar dark side. A range of monotonic conductivity profiles is calculated that provides a fit to the normalized data curve within error limits. Deeper than 90 km into the moon, the conductivity rises from 0.0003 mhos/m to 0.01 mhos/m at 1000 km depth. These conductivities, when converted to temperatures for an assumed lunar material of peridotite, suggest the existence of a thin outer layer (perhaps 90 km thick) in which the temperature rises sharply to 850 to 1050 K, then increases gradually to 1200 to 1500 K at a depth of about 1000 km.

Dyal, P.↗
NASA NTRS1971

The magnetism of the moon

Lunar magnetic fields measured by magnetometers placed by Apollo 12 and 14 astronauts, considering permanent fields due to fossil magnetic material and transient fields

Dyal, P.↗
NASA NTRS1971

Lunar electrical conductivity profile

Lunar electrical conductivity profile measurements, providing mantle-core stratification near surface thermal gradient, heat flux and composition data

Colburn, D. S.↗
NASA NTRS1971

Induced and permanent magnetism on the moon - Structural and evolutionary implications.

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.

Sonett, C. P.↗