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Session 33 - Dynamics of Solar Magnetic Fields.
Oral session, Tuesday, June 11
Wisconsin Center,

[33.09] Is a Dynamo Process Essential for Explaining the Solar Cycle?

P. A. Sturrock (Stanford U.)

The magnetic field at the solar photosphere is highly structured and time-variable, suggesting that it is generated and regenerated by a dynamo process that occurs within or at the base of the convection zone. However, it is proving difficult to explain all the properties of the solar cycle, and to match the rotational velocity profiles obtained by means of helioseismological observations, within the context of a dynamo model. Furthermore, there is some evidence that the neutrino flux is time varying, and that the variation is correlated with the solar cycle. This fact, if it proves to be correct, would be difficult to understand on the basis of a dynamo model, unless the neutrino has a magnetic moment, which would require that the neutrino has a non-zero mass.

For these and other reasons, it is perhaps prudent to question the assumption that dynamo action is essential for explaining the solar cycle. One way to seek to determine whether dynamo action is essential is to look for an alternative.

If the neutrino flux is time variable, this may indicate that nuclear burning is not steady, in which case it is likely that it is not spherically symmetric either. Nuclear burning that is neither steady nor spherically symmetric must be expected to lead to hydrodynamic flows within the Sun. It will be argued that a certain flow pattern, and a certain associated magnetic field pattern, can readily reproduce some of the salient properties of the solar cycle.

This work was supported in part by Air Force grant F49620-95-1-008 and NASA grant NAGW-2265.

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