Static compression of porous dust aggregates

¹ Department of Astronomical Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI) Mitaka, 181-8588 Tokyo, Japan
e-mail: akimasa.kataoka@nao.ac.jp
² National Astronomical Observatory of Japan, Mitaka, 181-8588 Tokyo, Japan
³ Institute of Low Temperature Science, Hokkaido University, Kita, 060-0819 Sapporo, Japan
⁴ Department of Physics, Nagoya University, Nagoya, 464-8602 Aichi, Japan
⁵ Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, 152-8551 Tokyo, Japan
⁶ Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, 275-0016 Chiba, Japan

Received: 20 February 2013
Accepted: 11 March 2013

Abstract

Context. In protoplanetary disks, dust grains coagulate with each other and grow to form aggregates. While these aggregates are growing by coagulation, their filling factor φ decreases to φ ≪ 1; however, comets, the remnants of these early planetesimals, have φ ~ 0.1. Thus, static compression of porous dust aggregates is important in planetesimal formation. However, the static compressive strength has only been investigated for relatively high-density aggregates (φ > 0.1).

Aims. We investigate and find the compressive strength of highly porous aggregates (φ ≪ 1).

Methods. We performed three-dimensional N-body simulations of aggregate compression with a particle-particle interaction model. We introduced a new method of static compression: the periodic boundary condition was 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 compressive strength of highly porous aggregates (φ ≪ 1). We check the validity of the compressive 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 (φ > 0.1) and confirm that our results consistently connect to those in the high-density region. The compressive strength formula is also derived analytically.