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  • 1
    Electronic Resource
    Electronic Resource
    Facular influences on the apparent solar shape (1983)
    [s.l.] : Nature Publishing Group
    Nature 301 (1983), S. 133-134 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The facular contribution to the light intensity can quite generally be represented by the formula6: = /pXAf^[ap + 6p/*+cp^2]Fc(M) (1) /ob.-/n where 7ob. is the observed specific intensity in an active region, /P is the same quantity for the undisturbed photosphere, A( is the facular area, Fc ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/301133a0
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  • 2
    Electronic Resource
    Electronic Resource
    The WIND magnetic field investigation (1995)
    Springer
    Space science reviews 71 (1995), S. 207-229 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and associated electronics. The dual configuration provides redundancy and also permits accurate removal of the dipolar portion of the spacecraft magnetic field. The instrument provides (1) near real-time data at nominally one vector per 92 s as key parameter data for broad dissemination, (2) rapid data at 10.9 vectors s−1 for standard analysis, and (3) occasionally, snapshot (SS) memory data and Fast Fourier Transform data (FFT), both based on 44 vectors s−1. These measurements will be precise (0.025%), accurate, ultra-sensitive (0.008 nT/step quantization), and where the sensor noise level is 〈0.006 nT r.m.s. for 0–10 Hz. The digital processing unit utilizes a 12-bit microprocessor controlled analogue-to-digital converter. The instrument features a very wide dynamic range of measurement capability, from ±4 nT up to ±65 536 nT per axis in eight discrete ranges. (The upper range permits complete testing in the Earth's field.) In the FTT mode power spectral density elements are transmitted to the ground as fast as once every 23 s (high rate), and 2.7 min of SS memory time series data, triggered automatically by pre-set command, requires typically about 5.1 hours for transmission. Standard data products are expected to be the following vector field averages: 0.0227-s (detail data from SS), 0.092 s (‘detail’ in standard mode), 3 s, 1 min, and 1 hour, in both GSE and GSM coordinates, as well as the FFT spectral elements. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the solar wind: (1) as a collisionless plasma laboratory, at all time scales, macro, meso and micro, but concentrating on the kinetic scale, the highest time resolution of the instrument (=0.022 s), (2) as a consequence of solar energy and mass output, (3) as an external source of plasma that can couple mass, momentum, and energy to the Earth's magnetosphere, and (4) as it is modified as a consequence of its imbedded field interacting with the moon. Since the GEOTAIL Inboard Magnetometer (GIM), which is similar to the MFI instrument, was developed by members of our team, we provide a brief discussion of GIM related science objectives, along with MFI related science goals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751330
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  • 3
    Electronic Resource
    Electronic Resource
    The quasi-stationary coronal magnetic field and electron density as determined from a Faraday rotation experiment (1970)
    Springer
    Solar physics 14 (1970), S. 440-456 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pioneer VI was launched into a circumsolar orbit on December 16, 1965, and was occulted by the sun in the latter half of November, 1968. During the occultation period, the 2292-MHz S-band telemetry carrier underwent Faraday rotation due to the interaction of this signal with the plasma and magnetic field in the solar corona. The NASA/JPL 210-ft diameter antenna of the Deep Space Network near Barstow, California, was used for the measurement. The antenna feed was modified for automatic polarization tracking for this experiment. The measurement results are interpreted with a theoretical model of the solar corona. This model consists of a modified Allen-Baumbach electron density and a coronal magnetic field calculated both from Mount Wilson magnetograph observations using a source surface model and field extrapolations from the Explorer 33 satellite magnetometer. The observations and the calculated rotation show general agreement with respect to magnitude, sense, and timing, suggesting the source-surface model and field extrapolations from 1 AU are a valid technique to obtain the magnetic field in the corona from 4 to 12 solar radii. Variations present can easily be ascribed to density enhancements known to be present in the corona. Longitudinal variations of the density in the corona cannot be obtained from coronagraph observations, and thus a purely radial variation was assumed. An improved fit to the Faraday rotation data is obtained with an equatorial electron density $$N = 10^8 \left( {\frac{{6000}}{{R^{10} }} + \frac{{0.002}}{{R^2 }}} \right)...{\text{ cm}}^{{\text{ - 3}}} {\text{ (4 〈 }}R 〈 12){\text{ }}...$$ where R is in solar radii. The work of W. V. T. Rusch and J. E. Ohlson was supported in part by research sponsored by the Joint Services Electronics Program through the Air Force Office of Scientific Research under Grant AF-AFOSR 69-1622A at the University of Southern California. The work done by K. H. Schatten was in part supported by the National Academy of Science on a National Research Council postdoctoral fellowship. The work of J. M. Wilcox was supported in part by the Office of Naval Research under Contract Nonr 3656(26), by the National Aeronautics and Space Administration under Grant NGR 05-003-230, and by the National Science Foundation under Grant GA-1319 at the University of California at Berkeley.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221330
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamo-based scheme for forecasting the magnitude of solar activity cycles (1991)
    Springer
    Solar physics 132 (1991), S. 1-40 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we present a general framework for forecasting the smoothed maximum level of solar activity in a given cycle, based on a simple understanding of the solar dynamo. This type of forecasting requires knowledge of the Sun's polar magnetic field strength at the preceeding activity minimum. Because direct measurements of this quantity are difficult to obtain, we evaluate the quality of a number of proxy indicators already used by other authors which are physically related to the Sun's polar field. We subject these indicators to a rigorous statistical analysis, and specify in detail the analysis technique for each indicator in order to simplify and systematize reanalysis for future use. We find that several of these proxies are in fact poorly correlated or uncorrelated with solar activity, and thus are of little value for predicting activity maxima. We also present a scheme in which the predictions of the individual proxies are combined via an appropriately weighted mean to produce a compound prediction. We then apply the scheme to the current cycle 22, and estimate a maximum smoothed International sunspot number of 171 ± 26, which can be expressed alternatively as a smoothed 2800 MHz radio flux (F 10.7) of 211 ± 23 × (10−22 Wm−2Hz−1), or as a smoothed sunspot area of 2660 ± 430 millionths of a solar disk. Once the actual maximum for cycle 22 has been established, we will have both additional statistics for all the proxy indicators, and a clearer indication of how accurately the present scheme can predict solar activity levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159127
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  • 5
    Electronic Resource
    Electronic Resource
    Transport of cosmic rays in the solar corona (1972)
    Springer
    Solar physics 23 (1972), S. 204-210 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A model is proposed to explain the transport of energetic protons in the solar corona. The particles are assumed to undergo an enhanced gradient-B drift along thin current sheets separating discontinuous field structures in the corona. These discontinuities may represent the extension into the corona of photospheric granular and supergranular cell boundaries. We have made a quantitative analysis of this process by assuming that the particle propagation can be described by a diffusion equation. Comparison of predictions of the model with cosmic ray observations at ∼ 1 AU provide some support for the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153904
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  • 6
    Electronic Resource
    Electronic Resource
    Motion of solar cosmic rays in the coronal magnetic field (1979)
    Springer
    Solar physics 62 (1979), S. 153-177 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Trajectories of solar cosmic rays have been calculated in a static ninth-order coronal magnetic field. It is found that as a result of field curvature and gradients, protons drift across the field lines at a rate of up to 200 γβ 2 deg hr−1. These drift rates are of the same order as, but somewhat smaller than, empirically derived rates. Localized enhancements of magnetic field have been inserted into the ninth-order field in order to model (in a highly idealized manner) the effects of the small-scale magnetic features which give rise to X-ray bright points. The motions of the particles in the presence of these scattering centers can be parameterized approximately by a cross-field diffusion coefficient. Our estimates of this coefficient, although crude, overlap with empirical values which have been deduced over a wide range of energies. We propose that coronal propagation of solar cosmic rays has two components. One is independent of particle velocity, and is associated with dynamic field phenomena (such as an expanding magnetic bottle): this is the only component which is important in flares which occur close to the foot-point of the Sun-Earth field line. The second component is velocity dependent, but is independent of mass, and is associated with scattering off (relatively static) magnetic inhomogeneities with scale sizes of at least 500 km: the second component contributes to coronal propagation if the flare occurs more than about 50–60 deg away from the Sun-Earth field line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150142
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  • 7
    Electronic Resource
    Electronic Resource
    Photospheric subrotation, differential rotation and zonal wind bands: A reverse pirouette (1981)
    Springer
    Solar physics 71 (1981), S. 169-173 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recently Mayr et al. (1980) have suggested that the superrotation of planetary atmospheres could, in principle, be understood as a ‘pirouette’. Equatorial heating is pumping atmospheric material toward the poles, and with a concomitant reduction in moment of inertia, the atmosphere has the tendency of spinning up. On the Sun, the core is assumed to be rotating with a period of about 12 days (Dicke, 1976; Knight et al., 1979) while the overlaying ‘mantle’ convection zone has a solid body component of about 27 days. We propose here that this phenomenon could simply be understood as a ‘reverse pirouette’. Our model is similar to the models put forth by Kippenhahn (1963), Weiss (1965), Durney (1968), Busse (1970), Yoshimura (1972), Gilman (1974), and Gierasch (1974). Whereas the models listed provided solutions of valid equations and computer analyses, they lack a simple physical picture to explain the phenomenon. In our case, we have the solar oblateness conventionally providing added heat input at the poles. The result is the large scale transport of material toward the equator giving rise to subrotation. The model thus facilitates an understanding of the formation of a slowly rotating convection zone above the more rapidly rotating core. The latitudinal photospheric differential rotation is interpreted as a ‘second order’ effect associated with horizontal momentum transport. The recent observations of zonal winds drifting equatorward with a 22-year period (Howard and LaBonte, 1980) may be related by this model as a third order effect from a similar periodicity in differential solar heating (pole to equator).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153616
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  • 8
    Electronic Resource
    Electronic Resource
    A ‘source surface theory’ corollary: The mean solar field-interplanetary field correlation (1970)
    Springer
    Solar physics 15 (1970), S. 499-503 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The correlation of the mean solar magnetic field and the interplanetary magnetic field reported by Wilcox et al. (1969) and Severny et al. (1970) has been interpreted by comparing the relationship of the measurement of the mean solar field with the physics involved in the formation of the interplanetary field. The high correlation observed is thus interpreted as a fortuitous correspondance between two integrals. The high correlation thus provides further support for the source surface model involved in these calculations. A new method is then suggested for observing the ‘mean solar field’ that might improve the correlations slightly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151854
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  • 9
    Electronic Resource
    Electronic Resource
    Venus' superrotation, mixing length theory and eddy diffusion: A parametric study (1988)
    Springer
    Earth, moon and planets 41 (1988), S. 45-76 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The Hadley mechanism is adopted to describe the axisymmetric four day superrotation in the Venus atmosphere, with solar driven meridional winds redistributing energy and momentum, and eddy diffusion describing the actions of three dimensional transient eddies. We address the question how the eddy diffusion coefficients are related to the properties of the circulation. For the atmosphere of a slowly rotating planet such as Venus, we show that a form of the non-linear closure is suggested by the mixing length hypothesis, which constrains the magnitude of the eddy diffusion coefficients. Combining this constraint with the concept of the Rossby radius of deformation yields zonal velocities on the order of 100 m sec−1. A steady state, non-linear, one-layer spectral model is used for a parametric study to find a relationship between heat source, meridional circulation and eddy diffusion coefficients, which yields the large zonal velocities observed. This analysis leads to the following conclusions: (1) Proportional changes in the heat source and eddy diffusion coefficients do not significantly change the zonal velocities. (2) The meridional velocity is virtually constant for large eddy diffusion coefficients. (3) Below a threshold in the diffusion rate, the meridional velocity decreases, commensurate with the mixing length hypothesis. Eddy heat conduction becomes important and shares with the Hadley cell advection in balancing the solar heating. The zonal velocities then reach large values near 100 m sec−1. (4) For large eddy diffusion and small heating rates, the zonal velocities decrease with decreasing planetary rotation rates. However, under condition (3), the zonal velocities are independent of the planetary rotation rate. Ramifications are discussed for related parameterizations in GCMs, emphasizing that eddy diffusion coefficients are governed by solar forcing and cannot be chosen independently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00113866
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  • 10
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    Transport of cosmic rays in the solar corona (1972)
    Springer
    Details
    Publication Date: 1972-03-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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