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  • Geophysics  (2)
  • stellar dynamos  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Magnetic field propagation in a stellar dynamo (1985)
    Springer
    Journal of statistical physics 39 (1985), S. 493-499 
    Details
    ISSN: 1572-9613
    Keywords: Numerical simulations ; stellar dynamos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from the solar butterfly diagram. When simulated at the base of the convection zone, the fields propagate in the right direction at roughly the right speed. However, owing to the numerical difficulty, a full magnetic cycle has not been simulated in this region. As a result, it is still uncertain where and how the solar dynamo operates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01008347
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    Paper (German National Licenses)
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  • 2
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    Advances in Modeling the Generation of the Geomagnetic Field by the Using of Massively Parallel Computers and Profound Optimization (2000)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: At the Earth's surface, the magnetic field that is observed is similar to that that would be generated by a simple bar magnet running through the Earth's axis. This idea (permanent magnetism) was commonly believed a century ago. Because the temperature of the core is so high, permanent magnetism is not possible. Therefore, the magnetic field should decay, over tens of thousands of years. Since it does not, the field must be regenerating. Since the turn of the century, the idea that the core is molten iron which by moving generates a magnetic field arose. The set of equations to describe this are extremely non-linear and complex. Only in the last five to ten years have computers been able to solve these equations.
    Keywords: Geophysics
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Three-Dimensional Simulations of Mantle Convection in Io (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Io has very high surface heat flow and an abundance of volcanic activity, which are thought to be driven by nonuniform tidal heating in its interior. This nonuniform heat is transported to the base of the lithosphere by very vigorous convection in Io's silicate mantle, the form of which is presumably responsible for the distribution of surface features such as volcanoes and mountains. We here present three-dimensional spherical calculations of mantle convection in Io, in order to ascertain the likely form of this convection and the resulting distribution of heat flow at the surface and core-mantle boundary. Different models of tidal dissipation are considered: the endmember scenarios (identified by M. N. Ross and G. Schubert) of dissipation in the entire mantle, or dissipation in a thin (approximately 100-km-thick) asthenosphere, as well as the 'preferred' distribution of M. N. Ross et al. comprising 1/3 mantle and 2/3 asthenosphere heating. The thermal structure of Io's mantle and asthenosphere is found to be strongly dependent on tidal heating mode, as well as whether the mantle-asthenosphere boundary is permeable or impermeable. Results indicate a large-scale flow pattern dominated by the distribution of tidal heating, with superimposed small-scale asthenospheric instabilities that become more pronounced with increasing Rayleigh number. These small-scale instabilities spread out the surface heat flux, resulting in smaller heat flux variations with increasing Rayleigh number. Scaled to Io's Rayleigh number of O(10(exp 12)) variations of order a few percent are expected. This small but significant variation in surface heat flux may be compatible with the observed distributions of volcanic centers and mountains, which appear fairly uniform at first sight but display a discernible distribution when suitably processed. The observed distribution of volcanic centers is similar to the asthenosphere heating distribution, implying that most of the tidal heating in Io occurs in an asthenosphere.
    Keywords: Geophysics
    Type: Icarus (ISSN 0019-1035); 149; 79-93
    Format: text
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    NASA TECHNICAL REPORTS
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