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# Useful Links

# Project Pages (Stuff currently on my plate - ordered by priority)

- Scrambler Paper
- Gravitationally induced turbulence
- Colliding Flows
- Thermally Unstable clouds
- MHD Clumps
- Mapping Out Cooling Regimes for Shocked Clumps
- The Morphological Impact of Cooling on Turbulence

# Recent Blog Entries

# Journal Clubs

# A few documentation things to fix

- contact us link on Download Page does not work if not logged in

- Instructions for installing AstroBEAR discuss using mercurial but don't mention where to check out the official 'repo' – which would of course only work for local folks anyways…

- AstroBearStandardOut needs to be updated to describe elliptic time usage. It would be helpful to also show some common errors that are seen.

- ModulesOnAstroBear
- does not discuss the ProblemBeforeGlobalStep subroutine
- Simulation data section should not encourage the use of numerical indices for things like px, or Energy as these will be dependent on equation of state, lMHD, nTracers, etc…
- Dimensions section should be updated since 1D problems are possible
- Dimensions section should also encourage the use of CellPos function to get (x,y,z from i,j,k)
- Units and scaling section should not encourage the changing of physical scales
- Initializing a Grid says that each infodef has a %dx which is not true
- Initializing a grid has an incorrect expression for the number of ghost zones
- Flagging cells for refinement implies that the errflag array extends into ghost zones – which it doesn't
- AdditionalPhysics says that MaintainAuxArrays needs to be set to true which is no longer correct
- Aux fields only need to be initialized if lMaintainAuxArrays is true (in 1D MHD it is false)
- Also an example that shows how to calculate the location of aux field entries would be good – as well as an example showing how to initialize a divergence free auxfield using a vector potential.
- It would be nice to stop storing the Cooling Objects in the chombo file – which would simplify the problem module.
- Not sure if selfgravity still has a problem with a uniform density field… this should be checked – and it would only be a problem with peridiodic BC's for the potential – also a discussion (or link to a discussion) about what needs to bet set in global.data for self-gravity to work.
- I believe you can have sink particles without self-gravity (ie just point gravity)

# Current Test

CurrentTests(johannjc_alfalfa, width=300)

Literature survey:

Klessen Heitsch MacLow 2000

- Collapse can only be prevented with unrealistically short wavelength driving
- Realistic driving ength gives observed core formation rates
- Discuss various dispersion relations for jeans analysis with turbulence
- Reference Bonazzola 1992 which has a critical spectra for support of alpha = 3 (outflow turb?)
- SPH and Lagrangian 3D Hydro Periodic 64 Jeans Masses
- Drive with various scales for 1 crossing time and then switch on self-gravity
- Forcing patterns described in MacLow 1998 and 1999

Heitsch Maclow Klessen 2000

- Similar to above but with MHD
- Density contrasts are lessened because of magnetic pressure
- Flow is organized into sheets - more clustered

Ossenkiof Klessen Heitsch

- Applied delta variance technique to self gravitating turbulence
- Periodic Box
- Density spectra has positive slope when self-gravity is important
- Propose to compare it with dust observations instead of 12CO to have a higher density contrast range
- 256
^{3}

Heitsch et al 2005

- Non-gravitating hydro colliding flows with cooling
- NTSI, KH, TI, but no discussion of Richtmeyer-Meshkov instability (Impulsive-accelerating RT instability)
- Look at 'core' properties (though 2D and no SG)

Heitsch et al 2006 "Birth of Molecular Clouds"

- Extended 2005 work to 3D
- no sg and hydro
- sinusoidal interface
- .5 particles/cc
- periodic (open in 2D)

Audit & Hennebelle 2005

- 2D colliding flows

Heitsch et al 2006 "Magnetized Non-Linear thin shell instability -2D"

- 2D MHD using PROTEUS
- Fields weaken or suppress NTSI

Heitsch et al 2006 "Cloud Dispersal in Turbulent Flows"

- no sg- looked at turbulent dispersal of clouds

Heitsch, Stone, and Hartmann 2008 "Effects of Magnetic Field Strencth and Orientation on Molecular Cloud Formation"

- Athena 3D 256
^{3}- no sg - mhd - Fields are important to resulting structure
- Fields normal to flow favor filamentary structure in collision plane
- Fields perpendicular to flow (ie y ) suppress ntsi along field axis (ky /= 0) and give an extended slab with filaments normal to field

Heitsch, Hartmann, and Burkert "Fragmentation of Shocked Flows: Gravity, Turbulence, and Cooling"

- Theory paper
- Star formation happens soon after MC formation
- Density enhancements are produced along with MC - problem with 'condensation models'
- Nead non-linear density enhancements - faster than gravity
- Discuss TI, GI, NTSI, KHI
- Phase diagrams with lines outlining dominate instabilities
- Dynamical and thermal instabilities dominate on small scales
- Thermal fragmentatation dominates gravitational fragmentation during cloud formation
- TI alone cannot produce jeans unstable clumps… need additional global compression

VazqueszSemadeni 2006

- Velocity perturbations

Inoue and Inutsuka 2012

- Colliding Flows in 3D
- Richtmyer-Meshkov instability
- No dynamical sg
- 1024
^{3}

## Radiation

Mixed frame

E_{r} F_{r} P_{r} are in lab frame - source terms in fluid frame

need closure relation Variable Eddington Tensor Stiff source terms (modified gudonov method) Wide range of timescales (implicit differencing)

Short characteristics Solve transfer equation across domain using time independent Stellar atmosphere code

Beam test Shadow test

Modified Gudonov method

source terms included in reconstruction step semi-implicit picard iteration scheme ensures stability

Fully implicit backward euler differencing - sparse matrix (no sub-cycling)

Aaron Skinner - reduced speed of light - semi-explicit (sub-cycling)

3 riemann solve 2nd order CTU with cfl .95

http://dl.acm.org/citation.cfm?id=1486457

SKIRT=code for 3D MonteCarlo radiative transfer in dusty systems…

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