Dynamics of aspherical dust grains in a cometary atmosphere: I. axially symmetric grains in a spherically symmetric atmosphere

• Published in: Icarus (New York, N.Y. 1962) Vol. 282; pp. 333 - 350
• Main Authors: Ivanovski, S.L., Zakharov, V.V., Della Corte, V., Crifo, J-F., Rotundi, A., Fulle, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.2017; Elsevier
• Subjects: Astrophysics; Coma; Comet nuclei; Comets; Dust; Dynamic tests; Dynamics; Earth and Planetary Astrophysics; Gas flow; Grains; Sciences of the Universe; Symmetry; Comets; Coma; Dust; Dynamics
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2016.09.024

•The spherical particles have the smallest maximum liftable size and therefore a model based on this approximation should under-populate the large size bins of the dust size distribution.•The difference in grain shape leads to velocity dispersion in space.•The difference in initial grain orientation, even for grains of the same shape, leads to velocity dispersion in space.•The aspherical particles make periodic motion which may change the observable cross-section of the grains. In-situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov–Gerasimenko. For the interpretations of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of the Stardust mission and analysis of samples of interplanetary dust have shown that these particles are highly aspherical, which should be taken into account in any credible model. The aim of the present work is to study the dynamics of ellipsoidal shape particles with various aspect ratios introduced in a spherically symmetric expanding gas flow and to reveal the possible differences in dynamics between spherical and aspherical particles. Their translational and rotational motion under influence of the gravity and of the aerodynamic force and torque is numerically integrated in a wide range of physical parameters values including those of comet 67P/Churyumov–Gerasimenko. The main distinctions of the dynamics of spherical and ellipsoidal particles are discussed. The aerodynamic characteristics of the ellipsoidal particles, and examples of their translational and rotational motion in the postulated gas flow are presented.