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  • 1
    Electronic Resource
    Electronic Resource
    Action spectrum for the effect of day-extensions on flowering and apex elongation in green, light-grown wheat (Triticum aestivum L.) (1989)
    Springer
    Planta 179 (1989), S. 428-432 
    Details
    ISSN: 1432-2048
    Keywords: Action spectrum ; Light-grown plants ; Photoperiodism ; Phytochrome (type I) ; Triticum (photoperiodism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluence-rate response curves for wavelengths from 640 nm to 730 nm were constructed for the day-extension promotion of flowering in green, light-grown, wheat (Triticum aestivum L., cv. Alexandria), a long-day plant. The resultant action spectrum had action maxima at 660 nm and 716 nm and resembles spectra for the high-irradiance reaction (HIR) seen in etiolated plants. Because, the HIR is thought to be controlled by type I pytochrome (that which is most abundant in etiolated tissue) our results indicate the involvement of type I phytochrome in the photomorphogenesis of a light-grown, green plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397581
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The kinetics of type 1 phytochrome in green, light-grown wheat (Triticum aestivum L.) (1994)
    Springer
    Planta 194 (1994), S. 136-142 
    Details
    ISSN: 1432-2048
    Keywords: Light and plant growth ; Photoperiodism ; Phytochrome (type 1) ; Triticum (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of type 1 phytochrome were investigated in green, light-grown wheat. Phytochrome was measured by a quantitative sandwich enzyme-linked immunosorbent assay using monoclonal antibodies. The assay was capable of detecting down to 150 pg of phytochrome. In red light, rapid first-order destruction of the far-red-light-absorbing form of phytochrome (Pfr) with a half-life of 15 min was observed. Following white light terminated by red, phytochrome synthesis was delayed in darkness by about 15 h compared to plants given a terminal far-red treatment. Synthesis of the red-light-absorbing form of phytochrome (Pr) was zero-order in these experiments. Phytochrome synthesis in far-red light was approximately equal to synthesis in darkness in wheat although net destruction occurred in light-grown Avena sativa tissues in continuous far-red light, as has been reported for other monocotyledons. In wheat, destruction of Pfr apparently did not occur below a certain threshold level of Pfr or Pfr/total phytochrome. These results are consistent with an involvement of type 1 phytochrome in the photoperiodic control of flowering in wheat and other long-day plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201044
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  • 3
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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
    Format: text
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  • 4
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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
    Details
    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
    Format: text
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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
    Details
    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
    Format: text
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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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    The effect of corotating interaction regions on the propagation of relativistic cosmic rays in the heliosphere (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: This paper questions the validity of modulation theories that ignore the presence of large regions of enhanced magnetic field in the heliosphere. The scatter-free and diffusive motion of relativistic cosmic rays is simulated in models of the heliospheric magnetic field, which include compressed field structures representing the corotating interaction regions that are believed to be present in the interplanetary medium throughout most of the solar cycle. It is found that the strong field gradients associated with these regions greatly perturb the drift pattern anticipated for simple Parkerian fields, and thus the expected streaming of cosmic rays from over the poles or along the current sheet, during consecutive solar cycles, no longer holds.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 87; June 1
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  • 8
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    Changes in cosmic ray propagation induced by corotating interaction regions (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: By simulating the trajectories for scatter free and diffusive propagation of relativistic cosmic rays in a model of the heliospheric magnetic fields containing a representation of corotating interaction regions (CIR's), it is found that, due to the large gradients associated with these compression regions, the motion is strongly affected and differs substantially from the predictions of current modulation theory. For positive (outward) northern hemisphere polarity, particles do not stream purely from high latitudes but can come from almost any latitude in the outer heliosphere; for negative polarity, many particles come along the current sheet (as predicted) but a second, equally important, population exists comprising particles that do not start on the current sheet but are brought to low latitudes by their interaction with CIR's. Thus, it is concluded that CIR's (and other large scale structures) cannot be ignored in analyses of cosmic ray modulation.
    Keywords: SPACE RADIATION
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  • 9
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    Asteroids: A source of natural resources for terrestrial and extra-terrestrial applications (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Keywords: ASTROPHYSICS
    Type: Lunar Science Inst., Abstracts of Papers Presented at a Special Session of the Seventh Annual Lunar Science Conference on Utilization of Lunar Materials and Expertise for Large Scale Operations in Space; p 143-147
    Format: application/pdf
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  • 10
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    Effects of drift on the transport of cosmic rays. IV - Modulation by a wavy interplanetary current sheet (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effect of a wavy interplanetary current sheet on the solar modulation of galactic cosmic rays is studied. A simple model of the heliospheric magnetic field is employed in which there is an Archimedean spiral magnetic field directed in one direction above the current sheet and another direction below. The current sheet itself is taken to be the extension by the solar wind of a surface that, at the sun, is a plane inclined at an angle alpha to the solar equator. Two magnetic sectors will therefore be seen by an observer within an angle alpha of the heliographic equator. A simple approximate model is used to investigate modulation. As the tilt angle alpha is increased from zero, it is found that the cosmic-ray intensity decreases. For reasonable variation of alpha from approximately 10 deg to approximately 30 deg, the change in intensity can be compared to that observed as one goes from solar minimum to solar maximum. It is concluded that changes in the waviness of the interplanetary current sheet can have an important, and perhaps dominant, effect in producing solar modulation of galactic cosmic rays.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 243
    Format: text
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