Inferring the interplanetary dust properties from remote observations and simulations

TL;DR

This study combines remote light scattering observations and simulations to infer interplanetary dust properties, revealing composition, temperature variations, and source contributions, especially from cometary dust and organics, across different heliocentric distances.

Contribution

It introduces a comprehensive model linking light scattering and temperature data to dust composition, size distribution, and origin, advancing understanding of interplanetary dust characteristics.

Findings

Good fit of polarization data with silicates and organics mixture

Dust temperature varies as R^{-0.45}, deviating from blackbody behavior

At least 20% of dust mass originates from comets

Abstract

Since in situ studies and interplanetary dust collections only provide a spatially limited amount of information about the interplanetary dust properties, it is of major importance to complete these studies with properties inferred from remote observations of light scattered and emitted, with interpretation through simulations. Physical properties of the interplanetary dust in the near-ecliptic symmetry surface, such as the local polarization, temperature and composition, together with their heliocentric variations, may be derived from scattered and emitted light observations, giving clues to the respective contribution of the particles sources. A model of light scattering by a cloud of solid particles constituted by spheroidal grains and aggregates thereof is used to interpret the local light scattering data. Equilibrium temperature of the same particles allows us to interpret the temperature heliocentric variations. A good fit of the local polarization phase curve, $P_{\alpha}$, near 1.5~AU from the Sun is obtained for a mixture of silicates and more absorbing organics material ($\approx$40 % in mass) and for a realistic size distribution typical of the interplanetary dust in the 0.2 to 200 micrometre size range. The contribution of dust particles of cometary origin is at least 20% in mass. The same size distribution of particles gives a solar distance, $R$, dependence of the temperature in $R^{-0.45}$ different than the typical black body behavior. The heliocentric dependence of $P_{\alpha=90{\deg}}$ is interpreted as a progressive disappearance of solid organics (such as HCN polymers or amorphous carbon) towards the Sun.