Nonlinear galactic dynamos and the magnetic pitch angle

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dc.contributor.authorChamandy, Luke
dc.contributor.authorTaylor, A. Russ
dc.date.accessioned2023-06-07T10:37:25Z
dc.date.available2023-06-07T10:37:25Z
dc.date.issued2015
dc.description.abstractPitch angles p of the large-scale magnetic fields B of spiral galaxies have previously been inferred from observations to be systematically larger in magnitude than predicted by standard mean-field dynamo theory. This discrepancy is more pronounced if dynamo growth has saturated, which is reasonable to assume given that such fields are generally inferred to be close to energy equipartition with the interstellar turbulence. This “pitch angle problem” is explored using local numerical mean-field dynamo solutions as well as asymptotic analytical solutions. It is first shown that solutions in the saturated or kinematic regimes depend on only five dynamo parameters, two of which are tightly constrained by observations of galaxy rotation curves. The remaining three-dimensional (dimensionless) parameter space can be constrained to some extent using theoretical arguments. Predicted values of∣p∣ can be as large as ~40, which is similar to the largest values inferred from observations, but only for a small and non-standard region of parameter space. We argue, based on independent evidence, that such non-standard parameter values are plausible. However, these values are located toward the boundary of the allowed parameter space, suggesting that additional physical effects may need to be incorporated. We therefore suggest possible directions for extending the basic model considered.en_US
dc.identifier.citationChamandy, L. et al. (2015). Nonlinear galactic dynamos and the magnetic pitch angle. Astrophysical Journal, 808 (1). 10.1088/0004-637X/808/1/28en_US
dc.identifier.issn1538-4357
dc.identifier.uri10.1088/0004-637X/808/1/28
dc.identifier.urihttp://hdl.handle.net/10566/9062
dc.language.isoenen_US
dc.publisherAmerican Astronomical Societyen_US
dc.subjectAstronomyen_US
dc.subjectPhysicsen_US
dc.subjectCosmologyen_US
dc.subjectGalaxiesen_US
dc.titleNonlinear galactic dynamos and the magnetic pitch angleen_US
dc.typeArticleen_US

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