The Solar Dynamo: Toroidal and Poloidal Magnetic Fields
Using the solar plasma flows as input (see The Solar Dynamo: Plasma Flows), the equations of magnetohydrodynamics, and 'seeding' the calculations with an initial small magnetic field, one can compute how a magnetic field can grow and be maintained. This is the dynamo process, the net result being that part of the Sun's outflowing thermal convective energy from nuclear processes is used to create the magnetic field.
In this view of the solar dynamo mechanism, we examine the evolution of the toroidal magnetic field, the field intensity represented by colors on the right-hand cross-section, and the poloidal magnetic potential field, represented by colors on the left-hand cross-section. The poloidal magnetic potential is a scalar quantity that contains information about the radial and latitudinal magnetic field vectors. To see the radial magnetic field, see The Solar Dynamo: Toroidal and Radial Magnetic Fields.
In this visualization, the magnetic field lines (represented by the 'copper wire' structures) are 'snapshots' of the field structure constructed at each time step of the model. These field lines should not be considered as 'moving' or 'stretching' as the model evolves in time.
Even this simplified model reproduces a number of characteristics observed in the actual solar magnetic field.
- Cyclic behavior with oscillations in the magnetic field amplitude.
- Magnetic regions at the surface migrate from high latitudes towards the equator as the solar cycle progresses. This reproduces the "Butterfly Diagram" pattern.
- Surface magnetic polarities reverse with each cycle
Because this model is axisymmetric, it cannot simulate non-axisymmetric features such as active longitudes.
For more information on the solar dynamo go to: http://svs.gsfc.nasa.gov/search/Series/SolarDynamo.html
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