[yt-users] Athena units

John ZuHone jzuhone at gmail.com
Thu Nov 21 18:43:36 PST 2013


Hi Stephanie,

In general, fields with the normal Athena names will be in code units, whereas the yt names will always be in cgs.

Roughly, it goes like this:

Density = cgs, density = code units
Pressure = cgs, pressure = code units
B[xyz] = cgs, cell_centered_B_[xyz] = code units
[xyz]-velocity = cgs, velocity_[xyz] = code units
momentum_[xyz] = code units

Note that the names are case-sensitive. Now, in yt-3.0 we will be adopting a different set of field names, but for now this should be good.

Best,

John

Sent from John ZuHone's iPad

> On Nov 21, 2013, at 8:43 PM, Stephanie Tonnesen <stonnes at gmail.com> wrote:
> 
> I am now looking at a few more variables, and am not sure whether I should be getting code units or physical units.  In the Athena vtk file, Pressure is one of the variables--will this be plotted in code units or will yt attempt to give me physical units since I am inputting some physical unit conversions in the load command?  Also , is "BMagnitude" in code units?  I am loading my data using the command:
> 
> 
> pf = load("id0/rps."+outstring[i]+"
> .vtk",parameters={"TimeUnits":9.78262,"LengthUnits":8.0236e22,"DensityUnits":9.999e-30})
> 
> 
> Thanks!
> 
> Stephanie
> 
> 
> 
>> On Mon, Oct 21, 2013 at 10:20 PM, Stephanie Tonnesen <stonnes at gmail.com> wrote:
>> Hi Again, Everyone!
>> 
>> So I would also like my figures to be in physical units, instead of in my code units.  I *think* the Athena frontend doesn't read in what the unit conversions are (and I am not sure how it would do that).  Can I just do something simple like:
>> 
>> DensityUnits = 3.
>> density_physunits = grid['density'] * DensityUnits
>> 
>> Then, of course, I don't know how I would do a SlicePlot, ProjectionPlot or phaseplot in physical units...
>> 
>> Any help/advice/direction is appreciated!
>> 
>> Thanks,
>> Stephanie
> 
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