Meeting update

Here is an outline of the ideas I am thinking for the ring analysis. The main idea is that the shocked material of the flows acquires some new density and velocity which translates into a ram pressure outward into the ambient medium. We can assume that when this material meets the ambient of equal pressure, the material will come to rest and that is where the ring will form. An issue is — we need a radial dependance of the pressure in the ambient (or from the splashing), so that we can find a radius where these 2 pressures balance.

Using just the shock conditions means we consider the splashed material having constant rho*v2. So what are the physical mechanisms that will provide a radial dependance on the pressure?

Here were some of my ideas (by the way, ignoring MHD for now):

-The splashed material slows down as it is being ejected from the collision region due to gravity — perhaps refer to Parker wind solutions (or something similar to Joe's analysis…, parker wind might not be the right term here for what I am thinking, but haven't looked into this yet… )

-The ambient medium is infalling toward the gravitational potential minima, i.e. the center of the box. This infall has some radial behavior —- and if I can back out the radial density and velocity profiles, will have a ram pressure to try and balance to the shock ram pressure

-Then more complicated stuff, like compression of the outgoing splashed material as it rams into the ambient gas, leading to cooling/loss of KE/and a concomitant decrease in velocity.

I focused on the 2nd case as it was the one I was most familiar. Although, it might not be entirely the right regime to do this analysis, depending on whether the ambient is fully jeans unstable. I thought it was a nice place to start, to jump into the equations, and the process of building the model.

Now, I am nearly done for the Hydro, nornmal shock situation, assuming no reflection. As you can see on this page, ways I can modify this model for the head on case:

  • making the shock reflected (expect small deviations from the values)
  • making the collapse not spherical but rather cylindrical (also don't expect much deviation)
  • adding magnetic pressure to the mix… probably here would get the greatest - change in the values… i.e. my model might fail the most because it doesn't include magnetic pressures at this point.

Here is a page describing the shock conditions I am using:

​https://astrobear.pas.rochester.edu/trac/wiki/u/erica/CFringanalysis

Here is a page describing the uniform collapse model I have been developing:

​https://astrobear.pas.rochester.edu/trac/wiki/u/erica/UniformCollapse

Uniform collapse involved:

  • understanding the solutions for uniform collapse again
  • couldn't find this easily on the web, so dug into the solutions myself
  • coded it up in mathematica to visualise the solutions
  • got the model nearly where it needs to be to begin using numbers from my sims to check it out

As there was no great description of this that I could find, either in text books or the web, I thought it would be good to write up what is in my notebook on the wiki. Need to try and get this visible in the google universe, as a search for uniform collapse sphere, or homologous collapse sphere, isn't bringing it up on google yet. Will check quickly if the visibility can be increased.

As far as papers, I have been reading astroph everyday, reading the highlights in astro on popular science sites, and have been reading the star formation newsletter.

I applied to Astrohack week but didn't get in the program. I have also been working through the equations and there importance in the Fed. paper on outflows.

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