Dispersal of protoplanetary disks by central wind stripping

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 pressure Wind pressure Curvature of the wind-disk mixing layer

6. Wind mass loss rate= 10-8 M yr-1 Disk 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×windvelocity×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