HL Tau: 3-D Polarisation Modelling and Magnetic Field Structure
We describe 3-dimensional Monte Carlo modelling of HL Tau in the near infrared with aligned non-spherical grains. JHK linear polarimetry with 0.4-0.6 arcsec resolution from Subaru and UKIRT is fitted in detail, providing information about the structure of the system, the grain properties and perhaps also the magnetic field. Circular polarisation models are also presented, showing how near infrared circular polarimetry will provide the key to measuring magnetic field structure in protostars on the scale of the solar system, provided that circular polarimeters become available. This is illustrated with recently obtained circular polarimetry of the intermediate mass YSO HH135.