  From a long time series of high resolution (R=115,000) HARPS spectra and
simultaneous broad-band photometry, we report new evidence for magnetospheric
accretion as well as ejection processes in the nearly edge-on classical T Tauri
star AA Tau.
  AA Tau's light curve is modulated with a period of 8.22d. The recurrent
luminosity dips are due to the periodic occultation of the central star by the
magnetically-warped inner disk edge located at about 9 Rstar. Balmer line
profiles exhibit a clear rotational modulation of high-velocity redshifted
absorption components with a period of 8.22 days as well, with a maximum
strength when the main accretion funnel flow passes through the line of sight.
At the same time, the luminosity of the system decreases by about 1 mag,
indicative of circumstellar absorption of the stellar photosphere by the
magnetically-warped, corotating inner disk edge. The photospheric and HeI
radial velocities also exhibit periodic variations, and the veiling is
modulated by the appearance of the accretion shock at the bottom of the
accretion funnel. Diagnostics of hot winds and their temporal behaviour are
also presented.
  The peculiar geometry of the young AA Tau system (nearly edge-on) allows us
to uniquely probe the acretion-ejection region close to the star. We find that
most spectral and photometric diagnostics vary as expected from models of
magnetically-channelled accretion in young stars, with a large scale
magnetosphere tilted by 20 deg onto the star's spin axis. We also find evidence
for time variability of the magnetospheric accretion flow on a timescale of a
few rotational periods.
