We assume that you have installed FARGO as explained here.
Run it on the template problem, by issuing in the
fargo directory the following command:
The code should begin to run. You should see the following output (we just reproduce the end of this output):
You should see a sequence of dots appearing on the last line. Every time a dot is issued, a hydrodynamic timestep is performed. This template problem simulates a Jupiter mass planet on a fixed circular orbit embedded in a thin () , viscous () protoplanetary disk. A carriage return is issued every 1/20th of orbit. An output of the hydrodynamics variables (density and velocities) is performed every orbit, so you need to wait for 20 lines of dots to be completed before you can have a look at the first output. While you are waiting for this first output, you can read what follows in order to launch the IDL widget that allows you to have a look at the results.
Open another xterm and go to the fargo directory. There, an IDL program called
mp.pro is provided in the distribution. In order to launch it, first start IDL:
then, under IDL, launch the widget:
The widget appears. We are first going to select the output number for which we want to display the variables. It will be output number 1 (number 0, already output at run start, is not very interesting : it has a uniform surface density, a null radial velocity...). In order to select the output number, locate the cursor labeled Fine near the top left part of the window. Move this cursor to position "1". "Output:1" is displayed in the window just above. This cursor and the one just below are used to select the output number. You can try to move both and see what output number you select, then come back to output number 1. Now we select the field we want to display. This is done in the Plot Selection field (it is in the middle of second column, just above the Read Value button). You can see that, by default, the gas density is displayed. However, since we are dealing with a large mass planet, we have a large ratio between the max and average value of the density field, so it may be a better idea to have a look at the logarithm of the surface density. Click on the second option of the Plot Selection field, named log Gas Dens.
Has the code reached output number 1 ? If not, it should in a short while. Wait for output 1 to be written, then click on the Gas Plot button (bottom row of buttons, fifth from the left). You should see the surface density response of the disk after one orbit, which begins to display the planet wake. The density field is shown in the (azimuth, radius) plane, with azimuth ranging from to , so the planet is "half on the left y-axis", "half on the right y-axis".
In order to represent the density field in a more intuitive manner (i.e. in polar representation), locate the Gas Polar Mode menu (it is located in the left column, in the large frame below the three cursors. You can see that by default the choice r-theta is selected. Select now x-y, then click again on the Gas Plot button (fifth from the left on the bottom row). You can now see the (log of the) density field in polar coordinates. If you now click on the Planet button (fourth to the right of Gas Plot), you see a circle around the planet location, which has a radius equal to the Hill radius of the planet. If you click on the Grid button, the zone interfaces are overlaid on the display. As the mesh resolution is not very low, the image gets very crowded.
Click on the Detail button to get a close-up of the planet. The Hill sphere and zone interfaces are displayed, as well as the velocity field in the planet frame. Finally, click on Default (left of Planet) to get back to the original picture. You can have a look at the successive outputs by moving the Fine cursor and clicking Gas Plot again. You can select which field you want to look at with the Plot Selection field. If you are patient enough to wait for output > 10-20, you can see how the planet begins to open a gap in the disk.
|Note: the IDL widget is provided as such. It is, it has always been and will always be in a beta version. Some of its functionalities are broken, some others are very problem specific. I do not have a comprehensive manual of it, neither do I plan to write one. However, understanding most of its functionalities should be straighforward. Also, note that since Fargo’s outputs are in raw format, the IDL widget should be run either on the same platform as Fargo, or at least on a platform that has the same floating points values endian conventions. If this is not the case, you should identify the
readu procedure calls in
mp.pro, and add a
/swap_endian option at the end of the corresponding
openr commands (see IDL manual for further details).
Note: If you do not have IDL to visualize FARGO outputs, you can use the tools developped by Aurélien Crida & Alessandro Morbidelli, based upon free software.
Alternatively, you can download a free IDL virtual machine from this address. Run it with this file that is a precompiled version of the widget:
mp.sav in the window that opens. Note that
mp.sav must reside in the
and the idl virtual manager must be lauched from this directory, otherwise you will get an error message.
Note: the template file provided is very close to the specifications for one of the runs of the EU hydrocode comparison project, except for the fact that no planet mass tapering is introduced over the first orbits (FARGO does not crash even if a full mass giant planet is instantaneously introduced in an initially unperturbed Keplerian disk).