# A question of personalities: evolution of viscous and wind-driven protoplanetary discs in the presence of dead zones

**Authors:** Simin Tong, Richard Alexander, Giovanni Rosotti  
**arXiv:** [2407.12209](https://arxiv.org/abs/2407.12209)  
**Date:** 2024-07-16  
**Summary page:** https://www.summarizepaper.com/en/paper/2407.12209v1/

## Key points

- Study title: "A Question of Personalities: Evolution of Viscous and Wind-Driven Protoplanetary Discs in the Presence of Dead Zones"
- Authors: Simin Tong, Richard Alexander, Giovanni Rosotti
- Main question addressed: Redistribution of angular momentum in protoplanetary discs by viscosity or magnetised winds
- Use of demographic indicators (gas disc sizes, stellar accretion rates) to distinguish between mechanisms
- Investigation of "hybrid" protoplanetary discs with both viscosity and magnetised winds, including dead zones
- Analysis on variations in disc properties (initial disc sizes, dead zone sizes, angular momentum transport efficiency)
- Impact on stellar accretion rates, disc surface density profiles, disc sizes, lifetimes, cumulative mass loss
- Findings show that removal of angular momentum by magnetised winds can sustain gas disc size expansion
- Influence of "disc personalities" on observed variations in disc sizes over time due to initial disc properties diversity
- Importance of considering individual characteristics when studying evolving protoplanetary systems
- Re-evaluation of association between demographic indicators and mechanisms for angular momentum transport in protoplanetary discs
- Need for additional diagnostics to differentiate between viscosity-driven redistribution and extraction by magnetised winds

## Summary

In their study titled "A Question of Personalities: Evolution of Viscous and Wind-Driven Protoplanetary Discs in the Presence of Dead Zones," authors Simin Tong, Richard Alexander, and Giovanni Rosotti address the longstanding question of whether the angular momentum of protoplanetary discs is redistributed by viscosity or extracted by magnetised winds. They explore how demographic indicators such as gas disc sizes and stellar accretion rates can be used to distinguish between these two mechanisms. Using one-dimensional gas simulations, the authors investigate the evolution of "hybrid" protoplanetary discs that are simultaneously driven by viscosity and magnetised winds, with dead zones present. Their analysis focuses on variations in disc properties including initial disc sizes, dead zone sizes, and angular momentum transport efficiency. They also examine how these variations impact stellar accretion rates, disc surface density profiles, disc sizes, disc lifetimes, and cumulative mass loss by different processes. The models demonstrate that when a majority of angular momentum is removed by magnetised winds for individual protoplanetary discs, the expansion of gas disc size can be sustained. However, the authors also find that when observing discs via demographic screenshots alone, the variation in disc sizes over time may be influenced by what they term as "disc personalities" – referring to the variations in initial disc properties among different discs. This highlights the importance of considering individual characteristics when studying evolving protoplanetary systems. Overall,this study re-evaluates the association between demographic indicators and mechanisms responsible for angular momentum transport in protoplanetary discs. The authors suggest that additional diagnostics are necessary to accurately differentiate between viscosity-driven redistribution and extraction by magnetised winds. Their findings provide valuable insights into the complex dynamics at play in evolving protoplanetary systems.