MPI-AMRVAC & CHARMing research · Code philosophy 1 Code philosophy 2 CHARM related example...

MPI-AMRVAC & CHARMing research

Rony Keppens

Centre for mathematical Plasma AstrophysicsKU Leuven

Rony Keppens (KU Leuven) MPI-AMRVAC 8-9 October 2012 1 / 31

Code philosophy

1 Code philosophy

2 CHARM related example applicationsWP1/WP4 themesWP2/WP5 themesWP3 themes

3 IAP opportunities


Code philosophy

• grid-adaptive, parallel MPI-AMRVAC code⇒ targets any set of equations of generic type

∂tU +∇ · F(U) = S(U, ∂iU, ∂i∂jU,x, t)

⇒ conserved variables U, fluxes F, sources S⇒ (near-) conservation laws: hyperbolic PDEs

• emphasis on shock-governed dynamics• full HTML documentation info at

http://homes.esat.kuleuven.be/~keppens


http://homes.esat.kuleuven.be/~keppens

Code philosophy

• subversion repository, recent reorganization to git⇒ https://gitorious.org/amrvac/amrvac⇒ develop/use Porth, Meliani, Xia, Marle, vd Holst, RK, . . .

• Test modules: advection and nonlinear scalar equations⇒ U = ρ, F = ρv with v uniform or v(ρ)⇒ nonlinear: profile steepens, shocks form,

compare Burgers to nonconvex


https://gitorious.org/amrvac/amrvac

Code philosophy

• Euler equations, with or without sources⇒ external gravity (planar or point)⇒ optically thin radiative losses (various cooling curves)

• Example with uniform gravity: Rayleigh-Taylor evolution


Code philosophy

• modern applications: circumstellar/binary environments⇒ Euler with optically thin radiative losses (van Marle et al.)

⇒ follow 3D evolution of orbiting stars


Code philosophy

Quadtree-Octree AMR

• example 2D domain covered by 8 = 4× 2 base level grid blocks⇒ hierarchically nested AMR levels, proper nesting⇒ fixed factor 2 refinement

1

2

4 5

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8 9

13

3

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14 15

16 17

• Space-filling Morton (Z -order) curve⇒ after every timestep: full grid-tree re-evaluated


Code philosophy

MPI-AMRVAC and HPC-Europa2

• excellent scaling: domain decomposition and multi-level AMR⇒ 2D MHD at ' 4002, 1000 ∆t in < 5 seconds (include IO)⇒ 10 level AMR special relativistic HD sustained 80%

efficiency on 2000 CPUs!


Code philosophy

Discretizations

• emphasis shock-capturing schemes, finite volume approach⇒ from TVDLF (readily used for any system) to successively

more advanced schemes, incorporating better approximations tothe local Riemann fans at cell interfaces

x

tttt

HLL HLLC HLLD Roe

• limited linear reconstruction (2nd to 3d order); PPM (parabolic)⇒ different discretization possible per grid level!


CHARM related example applications

1 Code philosophy


3 IAP opportunities


CHARM related example applications

• WP1/WP4: intracode comparisons, tool coupling⇒ (more) realistic reconnection physics (multi-physics)⇒ study interface dynamics (Kelvin-Helmholtz: grid vs SPH)

• WP2/WP5: confronting (solar/astrophysical) observations⇒ prominence modeling; data-driven CME initiation

• WP3: turbulence & particle acceleration⇒ turbulent dynamics in circumstellar & PWNe environments


CHARM related example applications WP1/WP4 themes

Multi-D MHD evolutions

• Harris sheet (tanh magnetic profile) evolution, fix resistivity η⇒ 2D resistive MHD, GEM Challenge⇒ reconnection at η = 0.005



• exactly same, at reduced resistivity η = 0.001

• on Macbook, effective 1920× 1920 resolution, several days . . .⇒ current evolution for η = 0.001⇒ schlieren plot evolution for η = 0.001

• Future plans: beyond resistive MHD (Hall-MHD)



• Kelvin-Helmholtz unstable v ∝ tanh yex -profile⇒ 2 dimensionless parameters: M = 1 MA = 10 (β = 120)⇒ role of B, without and with J-sheet

⇒ induced island formation (‘tearing’) when J-sheet



• 3D Kelvin-Helmholtz case study⇒ cylindrical jet, shear flow (width 2a) at circumference⇒ t = 0 parallel uniform B, V0 = 0.645, a = 0.05, B0 = 0.129⇒ reference parameters Ms = 0.5, Ma = 5, β = 120

• sideways ‘kink’ 3D perturbation⇒ ρ isosurface and vx = 0 jet surface colored by pth



• Nonlinear evolution for varying initial 3D perturbation⇒ field lines, density evolution



Solar physics: confronting observations

• Prominences suspended magnetically against gravity– up in corona, 100 denser, cooler than surroundings– 200 Mm long, 50 Mm high, 6 Mm wide– ‘quiescent prominences’ live months: stable equilibria!



• recent breakthrough: (Xia et al., 2012 ApJ Letter, April 1)simulating prominence formation in MHD!

⇒ thermal instability, runaway radiative cooling



• verify MHD force balance through the prominence structure(show current in cross-section)

⇒ gravity balanced by (upward) Lorentz force



• contemporary high resolution observations (Hinode)http://solarb.msfc.nasa.gov

⇒ lots of turbulent upflows⇒ from Berger et al., ApJ 2010, 716, 1288


http://solarb.msfc.nasa.gov


Rayleigh-Taylor in prominences

• local simulations: insight in ongoing dynamics(Rayleigh-Taylor instabilities, courtesy: C. Xia, Nanjing University)

• ultimate goals: simulate/confront/compare complex dynamics inactual eruption events (Solar Dynamics Observatory)http://sdo.gsfc.nasa.gov


http://sdo.gsfc.nasa.gov


• CME initiation scenarios⇒ Zuccarello et al., ApJ in press; 2001 April NOAA 9415

• magnetogram data to obtain potential background B0

⇒ finite β, gravitationally stratified, relax to MHS equilibrium⇒ apply twist (planar vortical flows on Bz isocontours)⇒ mimic observed photospheric flow patterns⇒ confront synthetic current maps with Soft X-ray view



• B topology after 700 Alfvén times⇒ after twisting, converging motions enforce actual eruption:

reproduce formation of flux rope, lift-off


CHARM related example applications WP3 themes

Structure formation in astrophysical setups

• Circumstellar bubbles & ‘turbulent’ structure⇒ van Marle & RK, 2012 A&A, in press

• 3D hydro+radiative losses for massive star environments⇒ mass loss & wind speed change from LBV to WR stage⇒ adiabatic compression at WR wind termination shock,

radiative at swept up LBV matter

R [cm]

log

10

(ρ)

[g/c

m3]

log

10

(p)

[erg

/cm

2]

0 5E+17 1E+18

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log10(ρ) [g/cm3]

log10(p) [erg/cm2]



• thin shell instabilities shape the 3D environment: density view

⇒ wind-wind interaction morphology varies with stellar massloss history



And even more exotic bubbles. . .

• Crab nebula, host of a pulsar with relativistic MHD wind bubble



• 3D (special) relativistic MHD simulations⇒ analytic/numeric control on ‘striped wind’ Poynting flux⇒ strong toroidal field wind zone, termination shock⇒ poloidal field creation, shocked wind redirected in jet⇒ synchrotron views: vortex shedding as ‘wisps’



• composite image in X-ray, visible, radio

⇒ upcoming seminar O. Porth at CmPA, October 23!


IAP opportunities

1 Code philosophy


3 IAP opportunities


IAP opportunities

• opportunities in IAP context (e.g. with SKIRT/AMUSE)⇒ enhanced postprocess to synthetic observations: AGN jets

⇒ improved radiative transfer/(M)HD feedback⇒ gravitationally controlled & shock-governed evolutions


IAP opportunities

• turbulent plasma dynamics⇒ particle acceleration at shocks/reconnection sites

• MHD to kinetic: solar wind modeling⇒ solar wind as MHD steady-state [ApJ 530 (2000)]

Confront multi-D views with kineticmodels, investigate dynamics be-yond ideal MHD, Hall-MHD recon-nection aspects, . . .


MPI-AMRVAC & CHARMing research · Code philosophy 1 Code philosophy 2 CHARM related example...

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