1. Dispersal of protoplanetary disks by central wind stripping Isamu Matsuyama University of California Berkeley David Hollenbach SETI Institute Doug Johnstone Herzberg Institute of Astrophysics

2. The outcome for a particular planetary system might be very different if the parent disk is dispersed faster or slower than in our solar system Disk dispersal mechanisms: Stellar encounters Planet formation Viscous accretion Photoevaporation Stellar wind stripping ? (Hollenbach et al. 2000, PPIV) Image credit: Dan Bruton

3. Wind stripping Previous studies: Hadbury & Williams (1976): stellar wind pushes the solar nebula as a whole. See also Cameron (1973), Horedt (1978, 1982). Elmegreen (1978): addition of low angular momentum wind material to the disk, the net radial flow is inward in this case. Wind-disk mixing layer moves outward Mass and momentum input from the wind Mass and angular momentum input from the disk Normal pressure balance

4. Mass, momentum, and angular momentum conservation; and normal pressure balance:

5. Normal pressure balance and mixing layer curvature Disk pressureWind pressureCurvature of the wind- disk mixing layer

6. Wind mass loss rate= 10-8 Myr-1Disk mass = 0.01 M, Wind velocity = 200 km s-1, Entrainment efficiency(ε) = 0.1 Wind mass loss rate= 10-8 Myr-1Disk mass = 0.01 M, Wind velocity = 200 km s-1, Entrainment efficiency(ε) = 0.1

7. Different entrainment efficiencies Canto and Raga (1991): ε = 0.01 – 0.1

8. Analytic approximation

9. “Early time”

10. “Intermediate time”

11. “Late time”

12. Summary Dispersal time proportional to mass of disk/ (wind mass loss rate×wind velocity×entrainment efficiency) When compared to photoevaporation and viscous evolution, wind stripping can be a dominant mechanism in a small range of outer disk only for the combination of – low accretion rates – High efficiency ε (> 0.1) – AND wind outflow rates approaching these accretion rates This case is unusual since generally outflow rates are < 0.1 of accretion rates