# hw4 - 2 Compare the surface density profile given in...

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Homework #4: Astronomy 155 Due Wednesday, March 24. 1. If the viscous timescale of a disk around a solar-mass star is about 1 million years, plot the relationship between ν (nu, the greek letter representing viscosity) and r (position in the disk). What I want you to do is to explore the values for the ‘effective’ viscosity in the context of a disk, to get a handle on what the typical numbers are. Take a range of r that go from 0.1 AU out to 100 AU. You’ll have to do a semilog or log-log plot. Compare these values (which can be thought of as the kinematic viscosity) to those of air at STP, water, and some other fluids. You can google values for those. Be sure that you are comparing the right kind of viscosity: the one we use is the kinematic viscosity as opposed to the dynamic viscosity. Also be careful of the units.
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Unformatted text preview: 2. Compare the surface density profile given in equation 3.20 (using 2-3 values for the mass accretion rate) with that of the minimum mass solar nebula (MMSN) surface density profile. Make a few plots to illustrate this comparison. Account for any differences between equation 3.20 and MMSN. 3. Generate a plot of the disk temperature as given in equation 3.30, for three different values of mass accretion rate (whatever reasonable values you choose). Specify what values you are using for the various other parameters. Compare this to the shape (T(r)) of the dust temperature profile obtained when using the Chiang and Goldreich (1997) approach, given in equation 2.42. Discuss the differences between the two different temperature profiles....
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## This note was uploaded on 09/08/2010 for the course ASTR 155 at San Jose State.

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