Thermal conductivity of porous aggregates

TL;DR

This study investigates the thermal conductivity of highly porous dust aggregates using N-body simulations, deriving an empirical formula that shows a quadratic relationship with the filling factor, impacting planetary thermal history models.

Contribution

It provides the first empirical formula for the thermal conductivity of fluffy dust aggregates based on N-body simulation data, highlighting a quadratic dependence on filling factor.

Findings

Thermal conductivity through the solid network is proportional to the square of the filling factor.

The thermal conductivity is significantly lower than previously assumed.

Results suggest a need to revisit thermal history models of small planetary bodies.

Abstract

$\mathit{Context.}$ The thermal conductivity of highly porous dust aggregates is a key parameter for many subjects in planetary science; however, it is not yet fully understood. $\mathit{Aims.}$ In this study, we investigate the thermal conductivity of fluffy dust aggregates with filling factors of less than $10^{-1}$. $\mathit{Methods.}$ We determine the temperature structure and heat flux of the porous dust aggregates calculated by $N$-body simulations of static compression in the periodic boundary condition. $\mathit{Results.}$ We derive an empirical formula for the thermal conductivity through the solid network $k_{\rm sol}$ as a function of the filling factor of dust aggregates $\phi$. The results reveal that $k_{\rm sol}$ is approximately proportional to ${\phi}^{2}$, and the thermal conductivity through the solid network is significantly lower than previously assumed. In light of these findings, we must reconsider the thermal histories of small planetary bodies.