Dispersal of protoplanetary disks by central wind stripping

Isamu MatsuyamaUniversity of California Berkeley

David HollenbachSETI Institute

Doug Johnstone Herzberg Institute of Astrophysics

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

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

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

Normal pressure balance and mixing layer curvature

Disk pressure Wind pressure Curvature of the wind-disk mixing layer

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

Different entrainment efficiencies

Canto and Raga (1991): ε = 0.01 – 0.1

Analytic approximation

“Early time”

“Intermediate time”

“Late time”

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