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Plasma Poynting-Roberson Effect on Fluffy Dust Aggregate

Plasma Poynting-Roberson Effect on Fluffy Dust Aggregate. T. Yamamoto Inst. Low Temperature Sci., Hokkaido Univ. In collaboration with T. Minato, H. Kimura (ILTS, Hokkaido U.) I. Mann, M. Koelher (Inst. Planetologie, Muenster U.).

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Plasma Poynting-Roberson Effect on Fluffy Dust Aggregate

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  1. Plasma Poynting-Roberson Effect on Fluffy Dust Aggregate T. Yamamoto Inst. Low Temperature Sci., Hokkaido Univ. In collaboration with T. Minato, H. Kimura (ILTS, Hokkaido U.) I. Mann, M. Koelher (Inst. Planetologie, Muenster U.)

  2. Dust around Young Main-Sequence Stars & in the Solar System • Observed in debris disk around young MS stars(Vega-like stars) & in the present solar system Dust disk around βPic IDP captured in the Earth atmosphere

  3. Dust around Young Main-Sequence Stars & in the Solar System • Dust in debris disk around Vega-like stars • Debris after formation of planetary systems? • In situ production by collisions of planetesimals? • Dust in the present solar system • Supply from comets, asteroid collisions & inflow of interstellar dust Dust must be supplied because of the limitation of its life time

  4. What limits the life time? Poynting-Roberson effect • Photon PR effect • Absorption and scattering of stellar photons • Plasma PR effect • Collisions of stellar wind ions

  5. radiation/wind pressure PR drag gravity Forces acting on a dust particle star

  6. PR drag Drag appears due to aberration on the particle in orbit Aberration angle

  7. Ratio of the plasma and photon PR drags • comparable to photon PR drag for the present solar system • dominant for the young MS stars

  8. Momentum transfer cross section • For photons: • Mie theory for spherical particles • DDA, … for aggregates • For charged particles: • Spherical particles • Mukai & Yamamoto 1982, A&A107, 97 • Perfect absorption • Minato et al. 2004, A&A, 424, L13 • Stopping power is taken into account. • Aggregates: Present study • Any shape & structure • Stopping power

  9. Models of dust aggregates (Mukai et al. 1992, Kimura et al. 2002) BPCA(Ballistic Particle-Cluster Aggregations) Fractal dimension BCCA (Ballistic Cluster-ClusterAggregations) cf. IDP

  10. Stopping power: Momentum transfer cross section Cross section : Distribution function of the thickness : Range of the incident stellar wind ions Small aggregates: Large aggregates: cf. radiation pressure cross section

  11. Momentum transfer cross sectionaveraged over the aggregate directions fluffyness geometrical cs penetration

  12. aggregate spheroid Empirical formula Momentum transfer cs Approximated to be the cross section for a spheroid of the same V and S.

  13. Dust around young main-sequence stars • Life time: limited by the photon PR drag (previous study) • Young MS stars • High mass-loss rate: • Luminosity: (Wood et al. 2002) Plasma PR drag will be dominant.

  14. Life time against the PR drag spherical silicate 10 AU to the star photon Life time is shorter for the aggregates wind plasma

  15. Implications • Rate of dust supply should be much larger than the previous estimates • Much larger number of planetesimals in the disk?

  16. Mass loss rate vs the age of stars Wood et al. 2002

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