astrobear - Blog
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About blog postsen-USTrac 1.4.1IonizationmccannFri, 02 Jun 2017 19:00:31 GMT
https://bluehound2.circ.rochester.edu/astrobear/blog/mccann06022017
https://bluehound2.circ.rochester.edu/astrobear/blog/mccann06022017<p>
Time stepping too large currently for parameters.
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<a href="https://bluehound2.circ.rochester.edu/astrobear/attachment/blog/mccann06022017/constant.gif" style="padding:0; border:none"><img crossorigin="anonymous" src="https://bluehound2.circ.rochester.edu/astrobear/raw-attachment/blog/mccann06022017/constant.gif" width="50%" /></a>
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To mimic Anjali's low flux case but instead with a solid sphere, let's use an ideal gas with the following setup:
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<span class="trac-mathjax" style="display:none">R_{\textrm{sphere}} = 1.5 \times 10^{10} \textrm{cm}</span>, <span class="trac-mathjax" style="display:none">L_{\textrm{domain}} = 6 R_{\textrm{sphere}}</span>, <span class="trac-mathjax" style="display:none">n_{\textrm{H, sphere}} = 6.0 \times 10^8 \textrm{cm}^{-3}</span>, <span class="trac-mathjax" style="display:none">n_{\textrm{H, ambient}} = 6.0 \times 10^6 \textrm{cm}^{-3}</span>, <span class="trac-mathjax" style="display:none">P_{\textrm{sphere}} = P_{\textrm{ambient}}</span>, <span class="trac-mathjax" style="display:none">T_{\textrm{sphere}} = 10^3 \textrm{ K}</span>, <span class="trac-mathjax" style="display:none">F = 2.0 \times 10^{13} \textrm{photons} \cdot \textrm{cm}^{-3}</span>.
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<a href="https://bluehound2.circ.rochester.edu/astrobear/attachment/blog/mccann06022017/multi.gif" style="padding:0; border:none"><img crossorigin="anonymous" src="https://bluehound2.circ.rochester.edu/astrobear/raw-attachment/blog/mccann06022017/multi.gif" width="50%" /></a>
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Grid aligned effectsmccannTue, 30 May 2017 06:28:15 GMT
https://bluehound2.circ.rochester.edu/astrobear/blog/mccann05302017
https://bluehound2.circ.rochester.edu/astrobear/blog/mccann05302017<p>
With the the planet creation correctly implemented, I've now rediscovered the grid aligned effects. Increasing resolution does not seem to resolve the issue, it only seems to exacerbates the issues of the grid aligned effects. That being the time step during the grid aligned effects is significantly smaller than after the planet reaches a steady state. At higher resolution it seems to use smaller time steps to resolve the effects.
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<a href="https://bluehound2.circ.rochester.edu/astrobear/attachment/blog/mccann05302017/lowres_movie.gif" style="padding:0; border:none"><img crossorigin="anonymous" src="https://bluehound2.circ.rochester.edu/astrobear/raw-attachment/blog/mccann05302017/lowres_movie.gif" width="45%" /></a> <a href="https://bluehound2.circ.rochester.edu/astrobear/attachment/blog/mccann05302017/128_movie.gif" style="padding:0; border:none"><img crossorigin="anonymous" src="https://bluehound2.circ.rochester.edu/astrobear/raw-attachment/blog/mccann05302017/128_movie.gif" width="45%" /></a>
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Hydrostatic equilibrium planetary atmospheremccannWed, 17 May 2017 17:00:43 GMT
https://bluehound2.circ.rochester.edu/astrobear/blog/mccann05172017
https://bluehound2.circ.rochester.edu/astrobear/blog/mccann05172017<h2 class="section" id="AstroBEARPlanetaryHSE"><em>AstroBEAR</em> Planetary HSE</h2>
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Currently the "hydrostatic" atmosphere is diffusing into the ambient. These runs take a couple of hours to get a few frames on 120 cores. From the images (left density, right pressure.) it appears the core of the planet is not being reset every time step as I intended it to. This is attempted by mimicking how the star is reset in your simulations; with the "surface" being the masked area of constant values deep interior the planet, and the "envelope" being the layer with variables as a function of <span class="trac-mathjax" style="display:none">r</span> and held steady. This is significantly different than the issue I had before and I am looking into why it has arisen. I'll email source code shortly.
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<a href="https://bluehound2.circ.rochester.edu/astrobear/attachment/blog/mccann05172017/gone.gif" style="padding:0; border:none"><img crossorigin="anonymous" src="https://bluehound2.circ.rochester.edu/astrobear/raw-attachment/blog/mccann05172017/gone.gif" width="45%" /></a> <a href="https://bluehound2.circ.rochester.edu/astrobear/attachment/blog/mccann05172017/gone_pressure.gif" style="padding:0; border:none"><img crossorigin="anonymous" src="https://bluehound2.circ.rochester.edu/astrobear/raw-attachment/blog/mccann05172017/gone_pressure.gif" width="45%" /></a>
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This could also be a resolution issue judging by the images. I don't see any further refinement (GmX=64<sup>3</sup>), when my global.data asked for 4 additional SMR levels (<a class="missing wiki">MaxLevel</a>=4, <a class="missing wiki">LastStaticLevel</a>=-1). Either the chombos or my Visit techniques are failing to plot the higher resolution I thought I had, or I misused the refinement feature in <em>AstroBEAR</em>.
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<h2 class="section" id="RadiativeTransferinATHENA">Radiative Transfer in <em>ATHENA</em></h2>
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The primary radiative energy considerations were previously recorded by Jonathan back in January <a class="ext-link" href="https://astrobear.pas.rochester.edu/trac/wiki/LineTransfer"><span class="icon"></span>(link)</a>. For reference on cooling rates, the recombination rate is taken from Osterbrock (1989), pg. 19 and Lyman alpha from Black (1981).
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To prevent large transients from the initial ionization of the neutral planet, the incoming flux is ramped by the function
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<span class="trac-mathjax" style="display:none">\frac{F(t)}{F_0} = 5\left(\textrm{erf}\left(\frac{t - 1.2\times 10^5}{8\times 10^4}\right)+1\right)+0.1.</span>
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The two constants within the error function prescribe when the function is at half value and the speed at which it ramps. Note <span class="trac-mathjax" style="display:none">F(0) = \frac{F_0}{10}</span> and <span class="trac-mathjax" style="display:none">\lim_{t\rightarrow \infty} F(t) = 10.1 F_0.</span>
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