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  • 1990-1994  (24)
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  • 1
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    Unknown
    On what intelligence is (1993)
    London, etc. : Periodicals Archive Online (PAO)
    British journal of psychology. 84:1 (1993:Feb.) 27 
    Details
    ISSN: 0007-1269
    Topics: Psychology
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0047-1993-084-01-000002
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The magnetic fields of active regions (1991)
    Springer
    Solar physics 135 (1991), S. 43-55 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Mount Wilson coarse array magnetograph data set is analyzed to determine characteristics of magnetic regions as a function of distance from the average latitude, ξ 0, of regions in each hemisphere, a quantity which varies during the activity cycle. Regions with normal polarity axis orientations are distributed asymmetrically about ξ 0 with the median latitude about 1 deg equatorward of ξ 0. Reversed polarity orientation regions show a somewhat broader and more symmetric distribution. Average sizes for regions at ξ = 0 (ξ 0) are nearly twice as large as those located at 10 deg latitude in either direction. Regions poleward of ξ 0 tend to show a net magnetic field biased toward the following polarity, and regions equatorward of ξ 0 are biased toward the leading polarity, both by around 10%. Neither region growth rates nor decay rates are related to ξ. The average polarity axis tilt angles of regions are lower for regions near the equator than for those nearer the poles. It is most likely that this is basically an effect of latitude rather than ξ. Meridional motions of young regions are shown to be toward ξ 0. Older regions do not show this behavior. This may be a magnetic effect rather than being due to large-scale circulatory motion, as has been suggested in the past. East-west inclination angles of active region magnetic fields show a slight tendency to trail the rotation direction (eastward inclination) by a few deg for regions with ξ 0〉 0 and lead the rotation (westward inclination) by a few deg for regions with ξ 0 〉 0. This effect may be related to the torsional oscillations. These various results are discussed in terms of a hypothetical subsurface magnetic flux tube which gives rise to the surface activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146697
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Axial tilt angles of sunspot groups (1991)
    Springer
    Solar physics 136 (1991), S. 251-262 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Digitized Mount Wilson sunspot data from 1917 to 1985 are analyzed to examine tilt angles determined from the area-weighted positions of leading and following sunspots. These spot group tilt angles are examined in relation to other group characteristics to give information which may relate to the formation and evolution of sunspot groups and the magnetic connection of groups to subsurface magnetic flux tubes. The average tilt angle of all 24816 (multiple-spot) group observations in this study is found to be + 4.2 ± 0.2 deg, where the positive sign signifies that the leading spots lie equatorward of the following spots. Sunspot group areas are significantly larger on average for groups nearer the average tilt angle, which is similar to a result found earlier for active region plages. Average tilt angles are found to be larger at higher latitudes, confirming earlier results. There is a strong negative correlation between average daily latitudinal motion (plus to poles) and group tilt angle. That is, for groups within about 40 deg of the average tilt angle, smaller tilt angles are associated with more positive (poleward) daily drift. Groups nearest the average tilt angle rotate the fastest, on average, the amplitude differences being between about +0.1 and − 0.1 deg day−1 for groups near and far from the average tilt angle, respectively. Groups with tilt angles near the average show a negative daily separation change between leading and following spots of close to 4 Mm day−1 on average. Groups on either side of the average tilt angle show spot separations that are on average more positive. A similar effect is not seen for the daily variations of group areas. These results are discussed in relation to analogous recent results for active region magnetic fields. More evidence is found for a qualitative difference between the magnetic fields of sunspots and of plages, relating, perhaps, to a difference in subsurface connection of the field lines or to different physical mechanisms that may play a role for fields of different field strengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146534
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  • 4
    Electronic Resource
    Electronic Resource
    A possible Coriolis-force contribution to the tilt-angle rotation of sunspot groups (1994)
    Springer
    Solar physics 149 (1994), S. 23-29 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The rotation of the magnetic axes of sunspot groups is studied as a function of the expansion and contraction of the groups along their magnetic axes. In general, except for the extreme values of tilt-angle change, slow rates of rotation of the magnetic axes are associated with low values of expansion or contraction, and faster rotation of the magnetic axes is associated with rapid expansion or contraction. The direction of rotation of the magnetic axes is related to expansion or contraction in the sense that would be predicted by the Coriolis force. A comparison of the effect at high and low latitudes shows a difference that further supports the Coriolis force hypothesis, and an examination of the amplitude of the effect also suggests that the Coriolis force may be a factor in the tilt-angle rotation of spot groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645175
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  • 5
    Electronic Resource
    Electronic Resource
    The rotation of active regions with differing magnetic polarity separations (1992)
    Springer
    Solar physics 142 (1992), S. 233-248 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The separation of the leading and following portions of plages and (multi-spot) sunspot groups is examined as a parameter in the analysis of plage and spot group rotation. The magnetic complexity of plages affects their average properties in such a study because it tends to make the polarity separations of the plages less than they really are (by the definition of polarity separation used here). Correcting for this effect, one finds a clear and very significant dependence of the total magnetic flux of a region on its polarity separation. Extrapolating this relationship to zero total flux leads to an X intercept of about 25 Mm in polarity separation. The average residual rotation rates of regions depend upon the polarity separation in the sense that larger separations correspond to slower rotation rates (except for small values of separation, which are affected by region complexity). In the case of sunspots, the result that smaller individual spots rotate faster than larger spots is confirmed and quantified. It is shown also that smaller spot groups rotate faster than larger groups, but this is a much weaker effect than that for individual spots. It is suggested that the principal effect is for spots, and that this individual spot effect is responsible for much or all of the group effect, including that attributed in the past to group age. Although larger spot groups have larger polarity separations, it is shown that the rotation rate-polarity separation effect is the opposite in groups than one finds in plages: groups with larger polarity separations rotate faster than those with smaller separations. This anomalous effect may be related to the evolution of plages and spot groups, or it may be related to connections with subsurface toroidal flux tubes. It is suggested that the polarity separation is a parameter of solar active regions that may shed some light on their origin and evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151452
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  • 6
    Electronic Resource
    Electronic Resource
    Editorial (1993)
    Springer
    Solar physics 143 (1993), S. vii 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619092
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    The magnetic fields of active regions (1990)
    Springer
    Solar physics 126 (1990), S. 299-309 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Mount Wilson coarse array data set is used to define active regions in the interval 1967 to August, 1988. From the positions of these active regions on consecutive days, rotation rates are derived. The differential rotation of the active regions is calculated and compared with previous magnetic field and plage rates. The agreement is good except for the variation with time. The active region rates are slower by a few percent than the magnetic field or facular rates. The differential rotation rate of active regions with reversed magnetic polarity orientations is calculated. These regions show little or no evidence for differential rotation, although uncertainties in this determination are large. A correlation is found between rotation rate and region size in the sense that larger regions rotate more slowly. A correlation between rotation rate and cycle phase is suggested which is in agreement with earlier sunspot results. Leading and following portions of active regions, unlike leading and following spots, show little or no difference in their rotation rates. The regions with polarity orientations nearest the normal configuration tend to show rotation rates that are nearest the average values. Most of these results generally support the conclusion that old, weaker magnetic fields have evolved different subsurface connections from the time they were a part of sunspots or plages. It seems possible that they are connected at a shallower layer than are sunspot or plage fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153052
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Sunspot group areas and the latitude distance from the average latitude of activity (1991)
    Springer
    Solar physics 135 (1991), S. 339-342 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Digitized Mount Wilson sunspot data from 1917 to 1985 are analyzed to examine group areas as a function of latitude distance (ξ) from the central latitude of activity in each hemisphere. On average these group areas are larger for the smallest values of ¦ξ¦. The effect is similar to that seen for the magnetic fields of active regions (Howard, 1991). It is concluded that this is fundamentally a ξ dependence, and not a latitude dependence. The suggestion is made that the cause of this effect is the influence of large-scale convective motions on the rising flux tubes that make up the active regions. The smaller flux tubes (spot groups) are more easily displaced in latitude during their ascent to the surface by this velocity field than are the larger flux tubes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147505
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  • 9
    Electronic Resource
    Electronic Resource
    The magnetic fields of active regions (1991)
    Springer
    Solar physics 132 (1991), S. 49-61 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Daily magnetogram data are analyzed to study the orientation angles of the magnetic axes of active regions defined by magnetic fields measured with the Mount Wilson magnetograph. The period covered by this daily data set is 1967 through April 9, 1990. The well-known tilt of the magnetic axes of active regions is seen clearly in these data. The dependence of tilt angle on latitude is different from that found by previous investigators, and it is suggested that this is due to the fact that this study uses all active regions, not spot groups or young active regions, and that there may be systematic variations in time of the tilt angles of regions. The variation of tilt angle with latitude is shown not to be a variation with cycle phase. Regions with smaller absolute tilt angles are larger than those with larger absolute tilt angles. Regions tilted in the normal orientation, with leading fields equatorward of following fields (positive tilt angles), are larger on average than those regions with negative tilt angles. Although there is no obvious relationship between tilt angle and daily region area change, it is found that regions with large tilt angles show on average rapid separation of the magnetic poles of the regions. This is not an effect of differential rotation shear. Normally oriented regions with small positive tilt angles rotate slower on average than those with small negative tilt angles. Some, but not all, of these results suggest that regions rise from subsurface flux ropes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159129
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  • 10
    Electronic Resource
    Electronic Resource
    How growth and decay of sunspot groups depend on axial tilt angles (1993)
    Springer
    Solar physics 145 (1993), S. 95-103 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Digitized Mount Wilson sunspot data covering the interval from 1917 to 1985 are analyzed to examine the average growth and decay rates of sunspot groups as a function of the tilt angles of the magnetic axes of the groups. It is found that in absolute terms, both growth and decay rates of groups peak at the average tilt angle of the groups (about +5°). In percentage terms these rates are a minimum near these tilt angles because average group areas are largest at the average tilt angle. The clear peaks at the average tilt angle (rather than at 0°) may be related to the structure or geometry of the subsurface flux loops that form the regions. One suggestion to explain this effect is that this is the angle that represents no twist of these subsurface flux loops. This implies, however, that these loops do not get twisted, on average, during their ascent to the surface by Coriolis forces, as has been suggested in the past. The average percentage growth rates for groups with negative tilt angles show high average values and large dispersions for certain tilt angle intervals, suggesting slower growth rates, for some unknown reason, for many small spot groups in certain tilt angle ranges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627985
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