Inferring the interplanetary dust properties

from remote observations and simulations

¹ Service d'aéronomie-IPSL-CNRS, UMR 7620, Route des Gâtines, BP 3, 91371 Verrières-le-Buisson, France e-mail: jeremie.lasue@aerov.jussieu.fr
² Université Pierre et Marie Curie-Paris6, Service d'aéronomie UMR 7620, 75005 Paris, France e-mail: chantal.levasseur-regourd@aerov.jussieu.fr
³ Laboratoire Interuniversitaire des Systèmes Atmosphériques, UMR 7583, Universités Paris 7 et Paris 12, 61 Av. du Général de Gaulle, 94010 Créteil, France e-mail: [fray;cottin]@lisa.univ-paris12.fr

Received: 10 April 2007
Accepted: 25 June 2007

Abstract

Context.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 scattered and emitted light, with interpretation through simulations.

Aims.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 particle sources.

Methods.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.

Results.A good fit of the local polarization phase curve, , near 1.5 AU from the Sun is obtained for a mixture of silicates and more absorbing organic material (≈40% in mass) and for a realistic size distribution typical of the interplanetary dust in the 0.2 μm to 200 μm size range. The contribution of dust particles of cometary origin is at least 20% in mass. The same size distribution of particles gives a dependence of the temperature with the solar distance, R, in R^-0.45 that is different than the typical black body behavior. The heliocentric dependence of is interpreted as a progressive disappearance of solid organic (such as HCN polymers or amorphous carbon) towards the Sun.