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  • 1
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    Radial and latitudinal gradients in the interplanetary magnetic field - Evidence for meridional flux transport (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Magnetic field data obtained by the Pioneer 10 and 11 spacecraft in the heliosphere from 1972-1982 and earth orbiting satellite data are examined in terms of radial and latitudinal gradients in the field components and magnitude. The data reveal that higher than expected gradients are observed in the magnetic field and time variations affect the field throughout the low-latitude heliosphere. It is determined that the high radial gradient is caused by meridional flux transport with low-latitude field lines moving to higher heliographic latitudes. High pressure near the solar equator and pressure due to heating in compressive solar wind interaction regions and the large field magnitudes that occur in these regions are investigated as mechanisms that produce the meridional flux. A solar cycle variation in the level of flux transport is analyzed.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 6760-676
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  • 2
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    The heliospheric current sheet - 3-dimensional structure and solar cycle changes (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The reversal in polarity of the interplanetary current sheet/sector structure is investigated during the recent solar maximum. Multipoint observations by ISEE-3 and Pioneer 11 show that a simple two sector or occasional four sector structure persisted throughout the maximum and out to distances of 10 AU. The polarity reversal occurred between March 1979 and October 1980, without any indication of an abrupt transition that might permit a more precise timing. The reversal coincided approximately with the reversal in the sun's polar cap fields. The current sheet appeared to be highly inclined during the ascending and descending phases of the solar cycle but was apparently too complex to describe as a simple inclined current sheet during solar maximum.
    Keywords: SOLAR PHYSICS
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  • 3
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    The effect of the heliospheric current sheet on cosmic ray intensities at solar maximum - Two alternative hypotheses (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The capabilities of two alternative models for accounting for the reversal of the solar magnetic field polarity at the point of solar maximum and for the associated modulation of cosmic ray intensities at 1 AU are assessed. One model posits a continuous increase in the inclination of the heliospheric current sheet to a point of verticality at maximum, when it overturns and the reversal occurs. The alternative view is that the sun sheds the magnetic field of the previous cycle and generates a new field of opposite polarity. Some data do exist for a tilted current sheet which increases its tilt with proximity to the solar maximum. However, coronal data also support the presence of isolated regions of anomalous polarity which spread over the surface of the sun as maximum approaches, a condition commensurate with flux shedding. Both models predict heliospheric current sheet configurations which would produce some cosmic ray modulations observed over the course of the solar cycle.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 2889-289
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  • 4
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    Filtering information from human experts (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The authors propose a model, or filter, for debiasing opinions from multiple experts and combining them into a single consistent estimate of some variable of interest. A distinguishing feature of the approach consists of making the calibration of experts an integral part of filtering. This enables the filter to learn from previous experience with the experts. The theoretical development takes a Bayesian perspective, using de Finetti's (1964) notion of exchangeability. Experimental results with a preliminary computer implementation of the filter show that its estimates are better than those from comparable filters that do not involve calibration.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Systems, Man, and Cybernetics (ISSN 0018-9472); 19; 6-16
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  • 5
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    Latitudinal extent of the heliospheric current sheet and modulation of galactic cosmic rays (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Possible correlations were investigated between the modulation of galactic cosmic rays and changes in the maximum heliographic latitude of the heliospheric current sheet during solar maximum. Solar photospheric magnetic field data from 1976-82 were extrapolated by means of potential theory to obtain the maximum latitudinal extent of the current sheet in the northern and southern hemispheres. The latitudinal differences were compared with terrestrial neutron flux data and Pioneer 10 data on cosmic rays with energies below 200 MeV at heliocentric distances of 10-30 AU. Account was taken for the time delay for the solar wind to propagate out to the spacecraft location. The current sheet maxima were nearly symmetrical about the solar equator except during sunspot maxima, when the solar poles were reversing. Significant changes in the latitudinal symmetry were highly correlated with the neutron data and cosmic fluctuations at Pioneer 10. The sensitivity of cosmic rays to the polarity reversals is in accordance with predictions of the gradient drift model.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 2933-294
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  • 6
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    Theoretical interpretation of the observed interplanetary magnetic field radial variation in the outer solar system (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of the azimuthal component of the IMF are evaluated through the use of an MHD model which shows the effect of magnetic flux tubes opening in the outer solar system. It is demonstrated that the inferred meridional transport of magnetic flux is consistent with predictions by the MHD model. The computed azimuthal and radial magnetic flux deficits are almost identical to the observations. It is suggested that the simplest interpretation of the observations is that meridional flows are created by a direct body force on the plasma. This is consistent with the analytic model of Nerney and Suess (1975), in which such flux deficits in the IMF arise naturally from the meridional gradient in the spiralling field.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 4378-438
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  • 7
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    Use of graphics in decision aids for telerobotic control: (Parts 5-8 of an 8-part MIT progress report) (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Four separate projects recently completed or in progress at the MIT Man-Machine Systems Laboratory are summarized. They are: a decision aid for retrieving a tumbling satellite in space; kinematic control and graphic display of redundant teleoperators; real time terrain/object generation: a quad-tree approach; and two dimensional control for three dimensional obstacle avoidance.
    Keywords: CYBERNETICS
    Type: JPL, California Inst. of Tech., Proceedings of the NASA Conference on Space Telerobotics, Volume 3; p 533-541
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  • 8
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    Variable force and visual feedback effects on teleoperator man/machine performance (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An experimental study was conducted to determine the effects of various forms of visual and force feedback on human performance for several telemanipulation tasks. Experiments were conducted with varying frame rates and subtended visual angles, with and without force feedback.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: JPL, California Inst. of Tech., Proceedings of the NASA Conference on Space Telerobotics, Volume 1; p 89-98
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  • 9
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    Adjustable impedance, force feedback and command language aids for telerobotics (parts 1-4 of an 8-part MIT progress report) (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Projects recently completed or in progress at MIT Man-Machine Systems Laboratory are summarized. (1) A 2-part impedance network model of a single degree of freedom remote manipulation system is presented in which a human operator at the master port interacts with a task object at the slave port in a remote location is presented. (2) The extension of the predictor concept to include force feedback and dynamic modeling of the manipulator and the environment is addressed. (3) A system was constructed to infer intent from the operator's commands and the teleoperation context, and generalize this information to interpret future commands. (4) A command language system is being designed that is robust, easy to learn, and has more natural man-machine communication. A general telerobot problem selected as an important command language context is finding a collision-free path for a robot.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: JPL, California Inst. of Tech., Proceedings of the NASA Conference on Space Telerobotics, Volume 1; p 81-88
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  • 10
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    Mars: Spectral signatures seen and unseen (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Intrepretation of Mars surface reflectance spectra and geochemical modeling of the surface material are different approaches to the same problem (determining the compositional nature and evolution of the surface of Mars). The degree to which these two approaches agree is studied. This study involves: current understanding of the reflectance of Mars, and reflectance spectra of proposed Mars constituents.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., MEVTV Workshop on Nature and Composition of Surface Units on Mars; p 25-27
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