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mkdiskfel - set up a test disk in a spherical potential filling f(E,Lz)
mkdiskfel out=snapshot [parameters=values ...]
sets up a disk of test particles launched from a specific axis (x or y)
in the gravitational potential of a user-supplied potential (in potential(5NEMO)
format), in order to get a reasonable sample of all possible orbits in
the allowed phase space of bound orbits. The initial condition will thus
look very boring, and after an integration with programs such as potcode(1NEMO)
and further analysis things will make more sense.
For testing there is an
option to only populate particles on a "maxlz" orbit. For symmetric potentials
these are the closed loop orbits, for core-harmonic but non-axisymmetric
these approach the loop orbits outside the core, but of course cannot follow
the bifurcation within the core. Need a cute figure to show this.
following parameters are recognized in any order if the keyword is also
Plotting the initial conditions
in a few phase-plot types for both a "maxlz" orbits alone, and the more
fully samples phase space is done as follows. The first three are the "maxlz"
- The data are written to this file in snapshot(5NEMO)
format . Currently the potential and total energy are stored in the Potential
and Aux slots of the snapshot. [no default].
- Number of bodies
particles [default: 2048]
- name of the potential(5NEMO)
- Paramaters to the user supplied potential.
The number of parameters depends on the potential supplied, the first parameter
is reserved for the pattern speed. [default: not supplied, parameters as
defined by potential(5)
- Optional data file(s) to the
user supplied potential. The number of files depends on the potential supplied.
[default: not supplied, or datafile(s) defined by potential(5)
- Inner cutoff radius of test-particle disk. [Default: 0].
- Outer cutoff radius of test-particle disk. [Default: 2].
energy of orbits. If a value is given, this currently triggers emax=emin
and all orbits will be sampled at this energy.
energy of orbits.
- Total mass of the disk. The default total
mass is 0, since this is a testdisk. Since there are a few programs that
will not like mass-less particles, this keyword can be used, or snapmass
will have to be used before further action is taken. [default: 0].
- Use random number seed. If 0 is given, a random number is generated from
the time of the day. [default: 0].
- Sign of the angular momentum. 1
means counter clockwise rotation in the XY-plane (in case you were wondering,
our galaxy has sign=-1). [Default: 1].
- Launch axis. Since all orbits
are in the X-Y plane, the options here are x or y.
- Try and find
only the maxlz orbits per energy/radius.
- Text headline
for output file [default: not used].
mkdiskfel - 2048 rmin=0.1 rmax=2 maxlz=t | snapplot - xvar=y yvar=-vx xrange=0:2
mkdiskfel - 2048 rmin=0.1 rmax=2 maxlz=t | snapplot - xvar=etot yvar=jtot
xrange=-1:-0.2 yrange=0:1.6 yapp=2/xs
mkdiskfel - 2048 rmin=0.1 rmax=2 maxlz=t | snapplot - xvar=y yvar=etot
xrange=0:2 yrange=-1:-0.2 yapp=3/xs
mkdiskfel - 2048 rmin=0.1 rmax=2 | snapplot - xvar=y yvar=-vx xrange=0:2
mkdiskfel - 2048 rmin=0.1 rmax=2 | snapplot - xvar=etot yvar=jtot
xrange=-1:-0.2 yrange=0:1.6 yapp=12/xs
mkdiskfel - 2048 rmin=0.1 rmax=2 | snapplot - xvar=y yvar=etot
xrange=0:2 yrange=-1:-0.2 yapp=13/xs
where in the last plot (13) you can clearly see the uniform sampling in
In the example below we explore non-axisymmetric potentials, non-rotating.
31-dec-2019 V0.1 drafted during the Top-2000 PJT
1-jan-2020 V0.4 finished sampling in E-r space PJT
2-jan-2020 V0.5 added emin= option to sample orbits at one energy PJT
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