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| Paper: |
A Magnetic Model for Acoustic Modes in roAp Stars |
| Volume: |
135, A Half Century of Stellar Pulsation Interpretations: a Tribute to Arthur N. Cox |
| Page: |
414 |
| Authors: |
Zita, E. J. |
| Abstract: |
If rapidly oscillating, peculiar A stars are not convective, then what drives their p- modes? Circumstantial evidence strongly suggests that roAp oscillations are causally linked to the stars' magnetic field. We present preliminary results to test our conjecture that p- modes in roAp stars are due to oscillations about a minimum magnetic energy configuration. We have shown that the dynamic edge region of a roAp star tends to be a force-free spherical shell. Force-free plasmas can oscillate about minima in the mean magnetic field energy. We have found the stable eigenstate for this energy minimum in a spherical shell, and characterized its dependence on the size of the force-free region and the amount of parallel current. We compare the characteristic wavenumbers, frequencies, and energies of resulting oscillations with observations of roAp stars, and present a model for p-mode oscillations in non-convective stars. Our work suggests the possibility of a nonlinear (turbulent) dynamo for such stars. |
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