1. Travis Metcalfe Space Science Institute + Stellar Astrophysics Centre Asteroseismic Signatures of Magnetic Activity Variations in Solar-type Stars Collaborators: W.A. Dziembowski, P.G. Judge, M. Snow, C. Karoff, W.J. Chaplin, R. Garcia, S. Mathur, D. Salabert

3. Goldreich et al. (1991) Magnetic perturbations modify the near-surface propagation speed Also leads to decreased convective velocity and change in temperature Secondary effects are required to explain the solar f-mode behavior

4. Metcalfe et al. (2007)

5. Parameterize shifts with  ~ A 0 (R / M) Q j (D c ) and fit MDI p-mode data A 0 ~ activity level, while the depth of the source D c ~ H p ~ L 1/4 R 3/2 / M Normalizing shifts by parametrization mostly removes dependencies

6. Metcalfe et al. (2007) Chaplin et al. (2007)

7. Salabert et al. (2011)

8. Mathur et al. (in prep.)

9. Overview Over the stellar cycle, magnetic activity induces shifts in the oscillation frequencies and reduces oscillation amplitudes by inhibiting convection. The first detection of both effects in CoRoT data supports the relation proposed by Dziembowski, with larger than solar shifts in a hotter star. The shortest cycles and the largest frequency shifts are expected in F stars, making them ideal targets for probing stellar activity with Kepler.