Bouncing Behavior of Microscopic Dust Aggregates

TL;DR

This study investigates how the internal structure of microscopic dust aggregates influences their bouncing behavior during collisions, revealing that realistic aggregates bounce only under specific conditions, which impacts planetesimal formation theories.

Contribution

It introduces a detailed molecular dynamics simulation approach to analyze how sample preparation affects dust aggregate bouncing, highlighting the importance of internal structure and collision parameters.

Findings

Realistic dust aggregates bounce only if volume filling factor exceeds 0.5.

Bouncing occurs at collision velocities below 0.1 m/s.

Internal structure significantly influences collisional outcomes.

Abstract

Context: Bouncing collisions of dust aggregates within the protoplanetary may have a significant impact on the growth process of planetesimals. Yet, the conditions that result in bouncing are not very well understood. Existing simulations studying the bouncing behavior used aggregates with an artificial, very regular internal structure. Aims: Here, we study the bouncing behavior of sub-mm dust aggregates that are constructed applying different sample preparation methods. We analyze how the internal structure of the aggregate alters the collisional outcome and determine the influence of aggregate size, porosity, collision velocity, and impact parameter. Methods: We use molecular dynamics simulations where the individual aggregates are treated as spheres that are made up of several hundred thousand individual monomers. The simulations are run on GPUs. Results: Statistical bulk properties and thus bouncing behavior of sub-mm dust aggregates depend heavily on the preparation method. In particular, there is no unique relation between the average volume filling factor and the coordination number of the aggregate. Realistic aggregates bounce only if their volume filling factor exceeds 0.5 and collision velocities are below 0.1 m/s. Conclusions: For dust particles in the protoplanetary nebula we suggest that the bouncing barrier may not be such a strong handicap in the growth phase of dust agglomerates, at least in the size range of 0.1 mm.