  We present an analysis of spectropolarimetric observations of the low-mass
weak-line T Tauri stars TWA 25 and TWA 7. The large-scale surface magnetic
fields have been reconstructed for both stars using the technique of Zeeman
Doppler imaging. Our surface maps reveal predominantly toroidal and
non-axisymmetric fields for both stars. These maps reinforce the wide range of
surface magnetic fields that have been recovered, particularly in pre-main
sequence stars that have stopped accreting from the (now depleted) central
regions of their discs. We reconstruct the large scale surface brightness
distributions for both stars, and use these reconstructions to filter out the
activity-induced radial velocity jitter, reducing the RMS of the radial
velocity variations from 495 m/s to 32 m/s for TWA 25, and from 127 m/s to 36
m/s for TWA 7, ruling out the presence of close-in giant planets for both
stars. The TWA 7 radial velocities provide an example of a case where the
activity-induced radial velocity variations mimic a Keplerian signal that is
uncorrelated with the spectral activity indices. This shows the usefulness of
longitudinal magnetic field measurements in identifying activity-induced radial
velocity variations.
