Plasma Poynting-Roberson Effect

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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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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 ßPic
IDP captured in the Earth atmosphere
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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
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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

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Forces acting on a dust particle
star
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PR drag
Drag appears due to aberration on the particle in
orbit
Aberration angle
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Ratio of the plasma and photon PR drags

• comparable to photon PR drag for the present
  solar system
• dominant for the young MS stars

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Momentum transfer cross section

• For photons
• Mie theory for spherical particles
• DDA, for aggregates
• For charged particles
• Spherical particles
• Mukai Yamamoto 1982, AA107, 97
• Perfect absorption
• Minato et al. 2004, AA, 424, L13
• Stopping power is taken into account.
• Aggregates Present study
• Any shape structure
• Stopping power

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Models of dust aggregates
(Mukai et al. 1992, Kimura et al. 2002)
BPCA (Ballistic Particle-Cluster Aggregations)
Fractal dimension
BCCA (Ballistic Cluster-Cluster Aggregations)
cf. IDP
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Momentum transfer cross section
Stopping power
Cross section
Distribution function of the thickness
Range of the incident stellar wind ions

Small aggregates Large aggregates
cf. radiation pressure cross section
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Momentum transfer cross sectionaveraged over the
aggregate directions
fluffyness
geometrical cs
penetration
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Empirical formula
Momentum transfer cs
Approximated to be the cross section for a
spheroid of the same V and S.
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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.
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Life time against the PR drag
spherical silicate 10 AU to the star
photon
Life time is shorter for the aggregates
wind plasma
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Implications

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

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