Supergranulation Scale Solar Surface Convection
Simulations
Dali GeorgobianiMichigan State University
Presenting the results of
Bob Stein (MSU) & Åke Nordlund (Denmark)with
David Benson (Kettering University)
progress report
Numerical Method
Staggered mesh
Non-linear, fully compressible, 3D, explicit
Spatial differencing:
6th order centered finite difference
Time advancement:
3rd order Runge-Kutta
Size and Resolution
• Size of the domain:
96 Mm x 96 Mm x 20 Mm
1000 x 1000 x 500 grid points
• Grid information:
dx = dy = 0.1 Mm
dz = 0.012–0.075 Mm
dt = 0.25 sec (saved every 60 sec)
Mean Atmosphere
(K)
(105 dynes/cm2)
(10-7 gm/cm2)
Vertical Velocity at 2.5 & 8 Mm depth
Boxes show domain of earlier simulations at 6, 12, 24 & 48 Mm widths.
Vertical momentum at 0, 2, 4, 16 Mm
Vertical momentum vs depth
Velocity stream lines
Courtesy Chris Henze (NASA)
Finite time Lyapunov exponent(proxy for vorticity)
Courtesy Bryan Green (AMTI/NASA)
Available Datasets
• Website http://sha.stanford.edu/stein_sim
(some info)
• Contact Bob Stein [email protected] (more info)
Simulated data are being ingested into the new SDO JSOC database
Thanks to Rick Bogart for his extensive help with archiving!
Archived Data Description
• 9 variables: horizontal velocities Vx, Vz, vertical velocity Vy, temperature, density, pressure, internal energy, electron density, and
• Each snapshot of a variable is stored in a separate file; 9 variables at each time step are combined to be retrieved together
• Data are in FITS format
• Duration 511 minutes (180 minutes recorded, WIP)
• A snapshot of a variable occupies approximately 2 GB of disk space
• First and third directions are horizontal, second direction is vertical
• Vertical grid is provided separately
(The data will be available for retrieval soon – check with Rick)
Another Data Set
• 4 hour averages, with 2 hour overlap
• 6 variables: horizontal velocities Vx, Vz, vertical velocity Vy, temperature, density, and sound speed
• Simultaneous surface velocities
• Stored in the IDL SAVE format at MSU
• Work in progress…
Units of Variables
• Length is in 108 cm = 1 Mm
• Time is in 102 s
• Velocities Vx, Vz, and Vy are in 10 km/s
• Temperature is in K
• Density is in 10-7 g/cm3
• Pressure is in 105 dynes/cm2
• Internal energy is in 105 ergs/cm3
• Electron density is log cm-3
These simulations provide an excellentopportunity to validate various techniques, widely used in solar physics and helio-seismology for directly obtaining otherwise inaccessible properties (subsurfaceflows, structures etc.)
On the other hand, these analysis techniques also help to examinehow realistic the simulations are
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