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At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Large scale photospheric magnetic field: The diffusion of active region fields

The large-scale phototospheric magnetic field was computed by allowing observed active region fields to diffuse and to be sheared by differential rotation in accordance with the Leighton (1969) magneto-kinematic model of the solar cycle. The differential rotation of the computed field patterns as determined by autocorrelation curves is similar to that of the observed photospheric field, and poleward of 20 deg. latitude both are significantly different from the differential rotation of the long-lived sunspots (Newton and Nunn, 1951) used as an input into the computations.

Schatten, K. H.↗
NASA NTRS1972

Magnetic field merging in the solar wind

Magnetic field merging in the solar wind is discussed in terms of steady-state merging, which involves a steady flow field, and of spontaneous merging, which involves an instability such as the tearing instability. Spontaneous merging is found to be more effective than steady-state merging.

Schindler, K.↗
NASA NTRS1972

Large-scale photospheric magnetic field - The diffusion of active region fields.

The large-scale photospheric magnetic field has been computed by allowing observed active region fields to diffuse and to be sheared by differential rotation in accordance with the Leighton (1969) magnetokinematic model of the solar cycle. The differential rotation of the computed field patterns as determined by autocorrelation curves is similar to that of the observed photospheric field, and poleward of 20 deg latitude both are significantly different from the differential rotation of the long-lived sunspots (Newton and Nunn, 1951) used as an input into the computations.

Schatten, K. H.↗
NASA NTRS1974

Change in blood coagulation indices as a function of the incubation period of plasma in a constant magnetic field

The influence of a constant magnetic field (CMF) with a strength of 250 and 2500 oersteds on the recalcification reaction and the tolerance of plasma to heparin was studied as a function of the exposure time of the plasma to the CMF. The maximum and reliable change in the activation of the coagulatory system of the blood was observed after a 20-hour incubation of the plasma in a CMF. As the exposure time increased, the recalcification reaction changed insigificantly; the difference between the mean arithmetic of the experiment and control values was not statistically reliable. The tolerance of the plasma to heparin as a function of the exposure time to the CMF of the plasma was considerably modified, an was statistically reliable.

Yepishina, S. G.↗
NASA NTRS1977

Interplanetary magnetic field and magnetospheric substorms

The interplanetary magnetic field (IMF) changes and the associated responses of the magnetosphere on November 1, 1972, are examined. IMF Bz changes consisted of a sudden southward turning, a slow northward turning, and a subsequent steady northward sense. Magnetospheric substorms occurred throughout this period.

Akasofu, S.-I.↗
NASA NTRS1981

Solar flare acceleration of solar wind - Influence of active region magnetic field

The direction of the photospheric magnetic field at the site of a solar flare is a good predictor of whether the flare will accelerate solar wind plasma. If the field has a southward component, high-speed solar wind plasma is usually observed near the earth about 4 days later. If the field has a northward component, such high-speed solar wind is almost never observed. Southward-field flares may then be expected to have much larger terrestrial effects than northward flares.

Lundstedt, H.↗
NASA NTRS1982

Onset of rapid mass loss in cool giant stars - Magnetic field effects

The possibility that closed magnetic field loops exist in steady state in stellar atmospheres in the HR diagram is examined. A model derived by Pneuman (1968) for helmet streamers in the solar corona is applied using a semi-empirical technique, to find that long-lived closed loops exist only below a certain boundary in the HR diagram. The region below this boundary is occupied by stars which are known to have hot coronae and slow mass loss. It is suggested that rapid mass loss sets in when closed field loops can no longer exist in steady state in the atmosphere.

Mullan, D. J.↗
NASA NTRS1983

Magnetic fields in the ionospheric holes of Venus - Evidence for an intrinsic field?

The suggestion that the radial magnetic fields observed in the regions of depleted plasma density in the nightside Venus ionosphere arise from an intrinsic planetary field was recently made by Knudsen et al. (1982). In this report the polarities of these radial fields, as measured by the Pioneer Venus Orbiter magnetometer, are examined in detail in order to determine if there is a geographical organization of the field polarity, or if the polarity of the radial field depends on the interplanetary field as previously proposed. The results of the data analysis indicate that a source in a planetary intrinsic field is unlikely.

Luhmann, J. G.↗
NASA NTRS1986

Low-frequency 1/f noise in the interplanetary magnetic field

Spacecraft observations of the interplanetary magnetic field at 1 AU are shown to have frequency spectra with a 1/f dependence in the range 2.7-80 microHz. It is suggested that the 1/f spectrum results from the superposition of uncorrelated samples of solar surface turbulence that have log-normal distributions of correlation lengths corresponding to a scale-invariant distribution of correlation times over an appropriate range of parameters.

Matthaeus, W. H.↗
NASA NTRS1999

Growth of II-VI Solid Solutions in the Presence of a Rotating Magnetic Field

The application of a rotating magnetic field (RMF)in the frequency range 60-400 Hz and field strength of the order of 2-8 mT to crystal growth has received increasing attention in recent years. To take full advantage of the control of fluid flow by the forces applied by the field, the liquid column must be electrically conducting. Also, the application of RMF to the directional solidification of a column of liquid can result in complete mixing in the resultant solid. Thus, the technique of RMF is suited to solvent zones and float zones where the composition of the liquid is more readily controlled. In the work we report on, numerical modeling has been applied to II-VI systems, particularly tellurium based traveling heater techniques (THM). Results for a spectrum of field strengths and acceleration levels will be presented. These show clearly the effects of competing buoyancy forces and electromagnetic stirring. Crystals of cadmium zinc telluride and mercury cadmium telluride have been grown terrestrially from a tellurium solvent zone. The effects of the RMF during these experiments will be demonstrated with micrographs showing etch pits, white beam x-ray synchrotron topographs and triple axis x-ray diffraction.

Gillies, D. C↗
NASA NTRS2000

Convection Induced by High Frequency Rotating Magnetic Field in Ionic Aqueous Solutions

Rotating magnetic fields (RMF) have found applications in modern metallurgy. Examples are casting and semiconductor crystal growth technology. Rotating convective flows can also be induced in ionic fluids. Due to optical transparency, these fluids offer a great opportunity to visualize convection. In this work, we investigate the dynamics of convection induced by a high frequency (100 kHz range) RMF. A dye injected into a cylindrical column of salty water serves as an indicator of the flow. The developed technique has been used to study mixing phenomena induced by a RMF both when the direc'tion of the field rotation is constant and when it is alternated. Optical recording has been used to analyze this process. A numerical model describing RMF mixing in the laminar regime will also be presented.

Volz, Martin P.↗