Movies of our simulation results


How to make astrophysical jets?

Below we present in inverse chronological order example results of our time-dependent MHD jet formation simulations.
These simulations follow the general framework of Blandford & Payne (1982), Ouyed & Pudritz (1997), and Casse & Keppens (2002,2004) and are using the ZEUS code and the PLUTO code.
The latest addition is based on our resistive version of the HARM code (Gammie et al. 2003, Noble et al. 2006). For details we refer to our published papers.

Check for results on
9) Accretion-ejection in GR-MHD, ---
8) Accretion-ejection dymano, --- 7) accretion-ejection simulations, ---
6) Formation of relativistic MHD jets, --- 5) formation of jets under radiation pressure, ---
4) Jets formation and reconnection flares, --- 3) formation of diffusive MHD jets, ---
2) Long-term evolution of stelalr dipoles, --- 1) jet formation aka Ouyed and Pudritz,


9) Accretion-ejection in GR-MHD (2017, 2018, 2019)

Here a fully relativistic approach is undertaken, applying resistive GR-MHD simulations, launching outflows and jets from rotating black holes and their surrounding accretion disk.

The simulations were done using our resistive version of the HARM code.

Publications are the following. Vourellis, Fendt, Qian, Noble, ApJ 882, 2V (2019),
Qian, Fendt, Vourellis, ApJ 859, 28Q (2018),
Qian, Fendt, Noble, Bugli (2017).

Movie A: GR-MHD of accretion-ejection. Color gradient shows mass density (left) and vertical speed v_z/c (right), both in log scale. Overlaid are poloidal magnetic field lines (black) and normalized poloidal velocity vectors (i.e directions; pink).
Magnetic flux is advected towards the BH, angular momentum loss by the disk wind leads to accretion. The poloidal magnetic field is bent torards the horizon (similar to the classical Wald solution). Due to resistivity the anti-aligned magnetic field along the equatorialplane inside the ISCO reconnects leading to a strongly turbulent Blandford-Znajek outflow. The disk outflow dominates the overall energy output.


Download simulation run ( .avi format, Size = 80 MB)

Movie B: GR-MHD of accretion-ejection. Same as above, but a sub-set of the innermost area. The red circle is the horizon, the yellow ellipse the ergosphere, the dark green circle indicates (!) the radius of the ISCO (located in the equatorial plane).



Download simulation run ( .avi format, Size = 130 MB)


8) Large-scale MHD simulations of accretion-ejection incl. a disk dynamo (2014)

Now applying a spherical grid. We also include a mean-field disk dynamo in the treatment and evolve the jet-driving magnetic field from a toroidal seed field.

Here are movies of our MHD simulations perfomed with the PLUTO code.

Publications are the following. Stepanovs, Fendt, Sheikhnezami, ApJ 796, 29S (2014)
for launching simulations with a disk dynamo-generated magnetic field, and
Stepanovs, Fendt, ApJ 825, 14S (2016),
Stepanovs, Fendt, ApJ 793, 31S (2014)
and Sheikhnezami, Fendt, Porth, Vaidya, Ghanbari, ApJ 757, 65 (2012)
for launching simulations concentrating on the ejection process, and
Fendt, Sheikhnezami, ApJ 774, 12 (2011)
for truly bipolar simulations.

Movie A: Long-term evolution of the jet disk system. Color gradient mass density. Contours indicate three magnetic flux surfaces.
Initially magnetic flux diffuses outwards untill ejection has established and removal of disk angular momentum leades to advection od mass and magnetic flux. This simulations runs for more than 500.000 dynamical time steps on a grid of more than 1000 inner disk radii. (The image shows the density map (left) and the vertical velocity map (right).



Download simulation run ( .avi format, Size = 50 MB)

Movie B: A disk dynamo-generated jet magnetic field. Color gradient mass density. Contours indicate three magnetic flux surfaces.
These simulations start from a purely (weak) toroidal magnetic field. The poloidal field driving the jet is generated by a alpha-Omega dynamo in the disk. The dynamo effieciently generates a strong poloidal field in the inner disk which then drives a jet. Poloidal magnetic flux loops are visible in the outer disk.



Download simulation run ( .avi format, Size = 170 MB)

Movie C: Time-dependent knot ejection Color gradient mass density. Contours indicate three magnetic flux surfaces.
Time-dependent knot ejection can be triggered by time-dependent dynamo action. Here we apply a dynamo toy model, by which the alpga-omega dynamo is switched on and off within a period of 2000 dynamical time. Knots are ejcted from the innermost disk in a similar time frame. (pictures show the ejection of two knots within a short time frame of the whole simulation run. Note the change of the color coding between the snapshots and within the movie).



Download simulation run ( .avi format, Size = 1 GB !!!!!)


7) MHD simulations of accretion-ejection structures (2012,2013)

Jets are launched by accretion disks. We numerical treat the accretion-ejection system, including the evolution of the disk structure. This finally provides the transfer rates for mass, energy and angular momentum.

Here are movies of our MHD simulations perfomed with the PLUTO code.

See Sheikhnezami, Fendt, Porth, Vaidya, Ghanbari, ApJ 757, 65 (2012)
for launching simulations concentrating on the ejection process, and
Fendt, Sheikhnezami, ApJ 774, 12 (2011)
for tryly bipolar simulations.

Movie A: Inner disk evolution - variation in the disk magnetization. Color gradient mass density. Contours indicate three magnetic flux surfaces. In the picture below, coloured contours correspond to ONE magnetic flux surface measured at different times.

Initially magnetic flux diffuses outwards untill ejection has established and removal of disk angular momentum leades to advection od mass and magnetic flux. A quasi steady state is reached after 2000 inner disk rotations (subject to the contineous disk mass loss).



Download simulation run ( .avi format, Size = 32 MB)

Movie B: Global evolution on one hemisphere. Here we show the global evolution of the system - launching from the disk into the jet, subsequent acceleration and collimation into a jet. Color gradient mass density. Contours indicate magnetic flux surfaces.



Download simulation run ( .avi format, Size = 42 MB)

Movie C: Global evolution on both hemispheres. This part of the project investigates the jet-counter jet asymmetries by truly bypolar simulations. The movie shows a symmetric evolution, th etest case of our model setup. Color gradient mass density. Contours indicate magnetic flux surfaces.



Download simulation run ( .avi format, Size = 12 MB)


6) Relativistic MHD simulations of jets from compact sources (2010,2011)

Relativistic jets originate in the direct vicinity of the massive black holes residing in the centers of most galaxies. Either they are launched as an initially sonic wind of the accretion disk or they originate directly in the black holes ergosphere transforming rotational energy into high Lorentz factors via magneto hydrodynamic processes.

Here are two movies of our RMHD simulations perfomed with the PLUTO code. Our papers investigate time-dependent special relativistic MHD simulations of jet formation from an accretion disk surface.

See Porth, Fendt, ApJ 709, 1100 (2010) for simulations of relativistic jet self-collimation, and
Porth, Fendt, Meliani, Vaidya, ApJ 737, 42 (2011) for mock observations of the simulated MHD data.

Movie A: Relativistic disk wind in a hourglass magnetosphere. Color gradient indicates the vertical velocity in units of c. Contours are: Field lines (white); electric current lines (green); light cylinder (blue).



Download simulation run ( .avi format, Size = 6.7 Mb)

Movie B: As the previous one but for a highly inclined split monopole geometry. The field-lines are pushed back into the disk surface and hence no steady state is established.



Download simulation run ( .avi format, Size = 6.7 Mb)


5) MHD simulations: jets from massive YSO affected by radiation pressure (2011)

This paper investigates time-dependent evolution of a superposed disk magnetic field with a stellar dipolar magnetosphere. See Vaidya, Fendt, Beuther, Porth, ApJ 742, 56 (2011).

Movie A: MHD jet under stellar radiation pressure Colors indicate velocity with a scale factor of 163 km/s.
Black Lines are magnetic field lines.
Radiation line-forces switched on after 319 disk rotations
Parameters: Mstar = 30 Msun, Rin = 1 AU, Alpha = 0.55, Qo = 1400.0, rho_0 = 5.0e-14 g/ccm



Download simulation run ( .avi format, Size = 6.7 Mb)

Movie B: MHD jet under radiative force of disk

Colors indicate velocity with scale factor of 515 km/s.
Black Lines are magnetic field lines.

Radiative force is added after 319 inner disk rotations.

Parameters: Mstar = 30 Msun, Rin = 0.1 AU, Alpha = 0.55, Qo = 1400.0, rho_0 = 5.0e-15 g/ccm



Download simulation run ( .avi format , Size = 39.0 Mb)

Movie C: Line-driven instability for run Disk2

Solid line is the evolution of the poloidal velocity after adding line force from disk. This is along field line rooted at r = 0.2 AU.

Dashed line is the poloidal velocity after steady MHD run.


Download movie of line instabilities ( .avi format , Size = 13.0 Mb)


4) MHD simulations: flaring disk-jet magnetospheres causing time-variable mass fluxes (2009)

This paper investigates time-dependent evolution of a superposed disk magnetic field with a stellar dipolar magnetosphere. (see Fendt, 2009, 692, 346 pdf-file).
Field distributions with aligned and anti-aligned magnetic axis of disk and stellar field are investigated. We use our version of ZEUS-3D extended for physical magnetic diffusivity, thus being able to follow reconnection events. The X-point of where anti-aligned disk field and stellar field meet along the disk surface gives rise to strong reconnection events with strong flares emerging across the jet magnetosphere. The flares evolve similar to coronal mass ejections changing the mass flux and velocity profile across the jet and also changing the mass flux number value by a factor of two to four with in short time. Our hypothesis is is that these flares initiate the observed jet knots. For our magnetic diffusivity model the time scales somehow fit.

The following gif-animations show the long-term evolution of the flow (use xanim).

Large frames, initial time steps (~3MB) Medium size frames, long run (~15MB)

Fewer frames, long run (~34MB) Large frames, long run (~35MB)

3) MHD simulations: magnetic diffusivity and jet collimation (2002)

In another paper we investigated the relation between the magnitude of jet magnetic diffusivity and the degree of jet collimation. (see Fendt & Cemeljic, 2002, A&A 395, 1045, pdf-file).
Diffusive jets are generally less collimated and there seems to be a critical value for the diffusivity (eta) above which the "jet" remains uncollimated. The jet velocities become faster with increasing diffusivity but the bow shock propagates slower (see density contours below with normalized eta = 0, 0.01, 0.1)



2) MHD simulations: a dipolar magnetosphere (1999)

Using the ZEUS 3D code in the axisymmetry option the evolution of a stellar dipolar-type magnetic field interacting with an accretion disk is calculated. The boundary condition is an inflow from a Keplerian disk (as in Ouyed and Pudritz 1997). In the movies the accretion disk is at the lower boundary. The initial magnetic field is locked in a rigidly rotating stellar surface and the disk. The size of the domain is 20x20 inner disk radii. Shown are density (colors) and poloidal field lines (black).

In the first simulation, the star is at rest. 100 Keplerian periods of the inner disk are calculated. A bubble forms disrupting the dipole. A disk wind accelerates and slowly collimates, indicating a possible final stationary state (Fendt & Elstner, 1999, A&A 349, L61,
pdf-file ).

Dipolar field, star at rest (~2MB)

In the second example the star rotates with a corotation radius at the inner disk radius. The initial field structure is a force-free dipole quenched along the equatorial plane. A two-component outflow (disk wind and stellar wind) is formed which is uncollimated. More than 2500 Keplerian periods of the inner disk are calculated in order to obtain a quasi-stationary final state (run S2). A larger stellar wind mass flow rate stabilizes the flow along the axis (run L5) (see Fendt & Elstner, 2000, A&A 363, 208 pdf-file). The following gif-animations show the long-term evolution of the flow (use xanim).

Small frames, long run (~11MB) Small frames, final time steps (~3MB)
Large frames, final time steps (~9MB) Medium size frames, long run (~25MB)
Large frames, long run (~35MB)



1) MHD jet formation simulations (1999) - the Ouyed and Pudritz model

Using the ZEUS-3D code in the axisymmetry option we calculated the jet formation from an accretion disk into a hydrostatic disk corona. The model of Ouyed and Pudritz (1997) is applied and used as reference for further simulations, e.g. of dipolar-type magnetic fields interacting with an accretion disk (below).

The jet runs from left (accretion disk) to the right (hydrostatic corona). Shown are density (colors) and poloidal field lines (black). The jet ACCELERATES and COLLIMATES.

Movie of the jet simulation (~1MB)

2010 Christian Fendt - last modified July 2010