Time Evolution of Protoplanetary Disk Size under Non-ideal Magnetohydrodynamics

Ray, Barshan (2025) Time Evolution of Protoplanetary Disk Size under Non-ideal Magnetohydrodynamics. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Barshan Ray (20MS109)) 20MS109_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Magnetic fields play an important role in the formation and evolution of an accretion disk around a protostar, also known as a protoplanetary disk. Recent studies, via simple assumptions, describe analytical methods linking the geometry of large scale magnetic fields threading a star forming core to the disk size, with ambipolar diffusion shown to be the primary nonideal MHD effect in alleviating the “magnetic catastrophe” which prevents Keplerian disk formation. These analytical descriptions have achieved good agreement with numerical experiments, and provide key insights into disk size population. To build upon this model, we implement the full solution for the self-similar collapse of an isothermal sphere as the envelope surrounding the core, which in turn yields the salient feature of this approach – the time evolution of the system. Through this time-dependent model, we investigate how the interplay between ambipolar diffusion and field accretion behaves over the inevitable time evolution of the backdrop of a collapsing gas envelope, to ultimately determine the disk size evolution. By applying the full solution for the evolving, collapsing envelope, we observe a disk radius and a central mass that grow sub-linearly over time, during early stages of collapse

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