Magnetic Doppler Imaging of Ap stars
J. Silvester, G.A. Wade, J.D. Landstreet, O. Kochukhov, S. Bagnulo

Abstract: We will introduce a project which exploits the unique polarimetric capabilities of ESPaDOnS to obtain high signal-to-noise ratio, high resolution, phase-resolved spectra of a selected sample of magnetic Ap stars in all 4 Stokes parameters. The resulting datasets will be used to construct detailed, assumption-free maps of the vector magnetic fields and chemical abundance structures in the photospheres of these stars using Magnetic Doppler Imaging. Such maps represent a crucial step toward understanding the origin and evolution of magnetic fields in upper-main sequence stars, and for constraining the influence of these fields on the chemical separation and mixing processes (e.g. diffusion, convection, mass loss) whose effects dominate the spectra of Ap stars.