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  • SOLAR PHYSICS  (8)
  • 1
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    On the contrast of facular hillocks in the infrared (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Faculae appear increasingly bright toward the limb of the sun. Recent observations also have shown that, in the infrared, these features appear dark at disk center. It is demonstrated that the hillock model of Schatten et al. (1986) can describe the essential features of these observations. In light of this model, a simple explanation is given for the contrast behavior of faculae. The observations are discussed in the context of the alternative well model.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 372; 728-732
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  • 2
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    Active region influences upon the solar constant (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The influence that active regions have upon the solar constant is discussed. Sunspots appear to lower the solar constant for the few days in which they are located near central meridian. This raises the possibility that an 11-year, solar-cycle-related depression in the solar constant may occur. Recent findings concerning the physics of active regions suggest that sunspots and faculae are largely surface features. Within that surface faculae reradiate, within a few weeks, the 'missing energy' associated with sunspots. This is consistent with the observations showing that the solar constant does not have an 11-year cycle-related depression that some authors predicted. However, there is a secular variation in the solar constant, whose explanation is not completely understood.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 818-822
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  • 3
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    A hillock and cloud model for faculae (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A hillock model is used here to explain facular contrasts, allowing faculae to emit more energy than the surrounding unmagnetized photosphere. For downflows, horizontal motions converge near the photosphere and many fibril flux tubes are drawn together to form a large dark area, the sunspot. For upflows, the motions diverge near the photosphere and fibril flux tubes are dispersed over a larger area associated with faculae. The upflows transport material and energy, resulting in hotter than normal temperatures, which in turn cause the gas to expand compared with its surroundings. Buoyancy thus causes a 'network' of patchy hillocks, clouds, or geysers to form which allows the sun to reradiate the energy deficit associated with sunspots by locally increasing the effective surface area of the sun beyond that of a sphere. The consequences of this model for the physical form of the facular manifestation, the appearance of faculae from earth, and the 'energy balance' in active regions are addressed.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 311; 460-473
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  • 4
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    Convection zone origins of solar atmospheric heating (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Spicules are examined as a means for supplying the corona with mass, energy, and magnetic field. It is suggested that spicules form from the supersonic upward expansion of material on nearly evacuated network flux tubes embedded within the sun's convection zone. This allows supersonic but subescape velocities to be attained by the material as it flows outward through the photosphere. Although supersonic, the kinetic energy (subescape) of the spicule material, as observed, is insufficient for coronal heating. It is suggested that, through buoyancy changes on evacuated flux tubes, the magnetic field first 'wicks' material flow into the solar atmosphere. Subsequently, the magnetic field energizes the gaseous material to form the conventional hot, dynamically expanding, solar corona. This occurs through momentum and energy transport by Alfven waves and associated Maxwell stresses concurrently flowing upward on these 'geysers' (spicules). The vertical momentum equation governing fluid flow is examined, and a particular equipartition solution is presented for the flow velocity along a simple field geometry.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 309; 864-873
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  • 5
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    Phlegethon flow: A proposed origin for spicules and coronal heating (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A model was develped for the mass, energy, and magnetic field transport into the corona. The focus is on the flow below the photosphere which allows the energy to pass into, and be dissipated within, the solar atmosphere. The high flow velocities observed in spicules are explained. A treatment following the work of Bailyn et al. (1985) is examined. It was concluded that within the framework of the model, energy may dissipate at a temperature comparable to the temperature where the waves originated, allowing for an equipartition solution of atmospheric flow, departing the sun at velocities approaching the maximum Alfven speed.
    Keywords: SOLAR PHYSICS
    Type: Coronal and Prominence Plasmas; p 401-405
    Format: application/pdf
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  • 6
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    Do faculae blanket sunspots? (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: If the hillock model for faculae (plages), in which the faculae are structures elevated above the photosphere, is correct, faculae may blanket sunspots. In this paper, the appearance of sunspots in relation to faculae areas and disk position is analyzed, leading to the conclusion that faculae blanket sunspots preferentially near the sun's limb. A computer model fitting the observation is used to infer an average height of 200 km for faculae. The possibility that plages obstruct the sunspot view is ruled out.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 347; 514-519
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  • 7
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    Energy Transport Below Sunspots and Faculae (1990)
    In:  CASI
    Details
    Publication Date: 2014-09-23
    Description: Sunspots and faculae were modeled using a modified stellar envelope code. Downflow velocities of 50 m/sec can achieve a 1,000 K drop in the surface temperature of the photosphere and reduce the surface irradiance to half its value. Concurrently, a 600 km Wilson depression forms that is associated with the enhanced density of the cooler gases. Similar upflow velocities provide for slightly enhanced temperatures and 150 km uplifted surfaces for faculae. The calculations show that, to first approximation, sunspot and facular structures (in density, temperature and pressure) can be obtained by simply vertically shifting the undisturbed photospheric materials to form wells and hillock geometries, respectively. However, the chromospheric manifestations of these features can be quite different owing to the influence of the magnetic field and flow.
    Keywords: SOLAR PHYSICS
    Type: Climate Impact of Solar Variability; p 50-5
    Format: application/pdf
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  • 8
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    Rotating convection and the solar differential rotation (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We discuss the implication of a numerical experiment on rotating convection and its relevance to the construction of a model for the solar differential rotation.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 152; 1; p. 283-290
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