Static compression of porous dust aggregates

TL;DR

This study investigates the static compression strength of highly porous dust aggregates in protoplanetary disks using N-body simulations, deriving a new empirical formula that extends understanding to very low filling factors.

Contribution

The paper introduces a novel simulation method for compressing porous dust aggregates and derives an empirical formula for their compression strength at very low densities, bridging a gap in existing research.

Findings

Derived an empirical compression strength formula for   aggregates.

Validated the formula across various simulation parameters.

Connected low-density results with previous high-density studies.

Abstract

Context: In protoplanetary disks, dust grains coagulate with each other and grow to form aggregates. As these aggregates grow by coagulation, their filling factor \phi decreases down to \phi << 1. However, comets, the remnants of these early planetesimals, have \phi ~ 0.1. Thus, static compression of porous dust aggregates is important in planetesimal formation. However, the static compression strength has been investigated only for relatively high density aggregates (\phi > 0.1). Aims: We investigate and find the compression strength of highly porous aggregates (\phi << 1). Methods: We perform three dimensional N-body simulations of aggregate compression with a particle-particle interaction model. We introduce a new method of static compression: the periodic boundary condition is adopted and the boundaries move with low speed to get closer. The dust aggregate is compressed uniformly and isotropically by themselves over the periodic boundaries. Results: We empirically derive a formula of the compression strength of highly porous aggregates (\phi << 1). We check the validity of the compression strength formula for wide ranges of numerical parameters, such as the size of initial aggregates, the boundary speed, the normal damping force, and material. We also compare our results to the previous studies of static compression in the relatively high density region (\phi > 0.1) and confirm that our results consistently connect to those in the high density region. The compression strength formula is also derived analytically.