Thinkshop 2020

Polarimetric observations of protoplanetary disks at millimeter wavelengths have been dramatically developing owing to its high-sensitivity and high-resolution observations with ALMA. However, the mechanisms of the polarization are under discussion. The proposed mechanisms so far are the self-scattering and the grain alignment, but the alignment directions are possibly with magnetic fields, with radiation fields, or with gas-drag directions. In this talk, I first review the possible mechanisms that may produce the millimeter polarization, and then present the case studies of different disks. On the lopsided disk of HD 142527, we found that the magnetic fields are dominated by the toroidal components at least in the south regions. On the ring-gap disk of HD 163296, by modeling the self-scattering polarization, we found that the dust scale height is lower in the inner regions, which indicates the low turbulence of gas in the inner disk and is consistent with the concept of magnetic dead zone. I also discuss possible constraints on the grain dynamics on AS 209 and HL Tau by modeling the gas-flow aligned dust grains.