Discrepancies in dynamical evolution of spherical and nonspherical cosmic dust particles
Authors:
M. Kocifaj
Image & caption:
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Image caption::
The minimum distance of particles from the Sun after the first revolution around the Sun.
The effective radii of the particles are 400 nm. The xy-plane is perpendicular to the ecliptic plane, i.e. y=0 for position angles alpha=90 deg. and alpha=270 deg. Orientation of the particle rotation axis is theta=60 deg. and phi=0 deg. The x- and y- positions as well as the minimum distance depicted in isolines are measured in solar radii. Particles are considered to be composed of magnesium-rich silicates.
Description:
The dynamical evolution of morphologically non-identical particles which are driven by gravity, electromagnetic radiation and the Lorentz forces can dramatically differ. Although spherical particles often enable analytical calculations, an orbital evolution of spheres cannot be considered as a representative evolution for real cosmic dust particles. Trajectories of the particles depend not only on the their shapes and sizes, but also on their chemistry and internal topology. For instance, the spherical dust particles ejected from comets will monotonously inspiral toward the Sun subject to the Poynting-Robertson effect. However, the nonspherical particles of the same origin may be temporarily stabilized at some heliocentric distances and thus their lifetime may be much longer than that for the Mie spheres. Some dust particles may be also captured in mean-motion resonances with planets (commensurability resonances). While spherical particles are always characterized by the secular decrease of the semi-major axes near mean-motion resonances, this may not be true for nonspherical particles. Resonant captures of arbitrarily shaped dust grains exist for exterior and interior mean-motion resonances with planets.
Reference:
Journal of Quantitative Spectroscopy & Radiative Transfer. ISSN 0022-4073, 2009, vol. 110, p. 879-888.
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