As part of an effort to properly define the thermophysical model of the lunar surface, experimental data have been obtained to determine the thermal conductivity of a particulate basalt sample (37 to 62 μ diameter) as a function of density in a simulated lunar temperature and pressure environment. A sample at six different densities ranging from 0.79 g/cm3 to 1.50 g/cm3 was investigated by using Ronald B. Merrill's method of thermal conductivity measurement. Recent measurements of the conductivity of the Apollo 11 lunar sample are included for comparison. Kenneth Watson's equation for the thermal conductivity of powders in a vacuum, K = A + BT3, has been curve‐fitted to the vacuum data for each density. The coefficients A and B are useful for application in thermophysical models of the lunar surface. Thermal conductivity data were also obtained under simulated Martian temperature and pressure environment at four of the densities. A separate effort was made to determine the maximum density obtainable with the specific sample to draw qualitative conclusions concerning the ambiguous value of density yielded by the Russian Luna 13 in situ density experiment. Thermal conductivity of particulate basalt was found to be a definite function of density in a simulated lunar environment and that function has been established. However, under simulated Martian environmental conditions, density and temperature had only a slight effect on thermal conductivity.

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The evolution of vector photospheric magnetic fields has been studied in concert with photospheric spot motions for a flare-productive active region. Over a three-day period (5-7 April, 1980), sheared photospheric velocity fields inferred from spot motions are compared both with changes in the orientation of transverse magnetic fields and with the flare history of the region. Rapid spot motions and high inferred velocity shear coincide with increased field alignment along the B L = 0 line and with increased flare activity; a later decrease in velocity shear precedes a more relaxed magnetic configuration and decrease in flare activity. Crude energy estimates show that magnetic reconfiguration produced by the relative velocities of the spots could cause storage of ~ 1032 erg day-1, while the flares occurring during this time expended ~< 1031 erg day-1.Maps of vertical current density suggest that parallel (as contrasted with antiparallel) currents flow along the stressed magnetic loops. For the active region, a constant-e, force-free magnetic field (J = eB) at the photosphere is ruled out by the observations.

The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models, and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in grain rotation and alignment has not been achieved. As there appear to be no experimental data available on this subject, we have carried out some unique experiments to illuminate the processes involved in the rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron /submicron-sized, nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of $10 À3 to 10 À5 torr. The particles are illuminated by laser light at 5320 8, and the grain rotation rates are obtained by analyzing the low-frequency ($0-100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in light of the current theories of alignment.