Alfvénic Heating of Protostellar Accretion Disks

We investigate the effects of heating generated by damping of Alfvén waves on protostellar accretion disks. Two mechanisms of damping are investigated, nonlinear and turbulent, which were previously studied in stellar winds. For the nominal values studied, f = δv/vA = 0.002 and F = ϖ/Ωi = 0.1, where δv, vA, and ϖ are the amplitude, velocity, and average frequency of the Alfvén wave, respectively, and Ωi is the ion cyclotron frequency, we find that viscous heating is more important than Alfvénic heating for small radii. When the radius is greater than 0.5 AU, Alfvénic heating is more important than viscous heating. Thus, even for the relatively small value of f = 0.002, Alfvénic heating can be an important source of energy for ionizing protostellar disks, enabling angular momentum transport to occur by the Balbus-Hawley instability.