Transcript Dust coagulation and motion

Brownian motion growth: self-similar
Dullemond & Dominik 2005
Sedimentation-driven growth („rainshower“)
One-particle model
Equator
Sedimentation-driven growth („rainshower“)
One-particle model
Equator
Sedimentation-driven growth („rainshower“)
One-particle model
Equator
Sedimentation-driven growth („rainshower“)
One-particle model
Equator
Warning: Not to scale! ;-)
Sedimentation-driven growth („rainshower“)
Equation of settling of the big dust grain:
dz(t)
rs a(t)
= vsett (z(t), a(t)) =
W2K z(t)
dt
rgas (z(t))v th
Equation of growth by sweep-up as the big grain falls:
dm(t)
2
= p a (t)rtinydust (z(t)) vsett (t)
dt
Relation between m(t) and a(t):
4p
m(t) =
rsolid a3 (t)
3
Distribution of the small dust:
æ z2 ö
÷
rtinydust (z) = 0.01 rgas (z) = 0.01
exp çç 2÷
2p H p
è 2H p ø
Sgas
Sedimentation-driven growth („rainshower“)
Dullemond & Dominik (2005)
“Rainshower” in a disk
Dullemond & Dominik (2005)
Parallel with meteorology
Rain falling from a cumulus congestus cloud
Now with convection
Dullemond & Dominik (2005)
Parallel with meteorology
Cumulonimbus cloud, most probably with severe hail
Parallel with meteorology
Layered structure of giant hail stone
Main problem: high velocities
30 m/s =
100 km/h !!
Particle size [meter]
Dust coagulation+fragmentation model
Σdust [g/cm2]
10-2
10-4
10-6
10-8
10-4
10-2
Grain size [cm]
Birnstiel, Dullemond & Ormel 2010
100
Dust coagulation+fragmentation model
Σdust [g/cm2]
10-2
10-4
10-6
10-8
10-4
10-2
Grain size [cm]
Birnstiel, Dullemond & Ormel 2010
100
Meter-size barrier
Growth from ‘dust’ to planetary building blocks
Meter-size barrier
Rapid radial drift
Aggregation
Brownian
motion
1m
Differential
settling
Fragmentation
Sweep-up growth
Turbulence
1mm
1m
1km
More barriers...
Growth from ‘dust’ to planetary building blocks
Charge barrier
Bouncing barrier
Meter-size barrier
Rapid radial drift
Aggregation
Brownian
motion
1m
Differential
settling
Fragmentation
Sweep-up growth
Turbulence
1mm
1m
Zsom et al. 2010, Güttler et al. 2010
Okuzumi 2009
1km
The “Lucky One” idea
Let’s focus on the fragmentation barrier
Growth from ‘dust’ to planetary building blocks
Meter-size barrier
Rapid radial drift
Aggregation
Brownian
motion
1m
Differential
settling
Fragmentation
Sweep-up growth
Turbulence
1mm
1m
1km
The “Lucky One” idea
Particle abundance
Low sticking efficiency
Windmark et al. 2012
How to create these seeds? Perhaps velocity distributions:
Garaud et al. 2013; Windmark et al. 2012
All the different collision outcomes...
Güttler et al. 2010
Fluffy grains, compaction, bouncing...
Zsom et al. 2010