Supergranulation Scale Solar Surface Convection Simulations progress report Dali Georgobiani Michigan State University Presenting the results of Bob Stein (MSU) & Åke Nordlund (Denmark) with David Benson (Kettering University)
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
Velocity stream lines Courtesy Chris Henze (NASA)
Finite time Lyapunov exponent (proxy for vorticity) Courtesy Bryan Green (AMTI/NASA)
Available Datasets Simulated data are being ingested into the new SDO JSOC database • Website http://sha.stanford.edu/stein_sim (some info) • Contact Bob Stein firstname.lastname@example.org (more info) 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 G1 • 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 excellent opportunity to validate various techniques, widely used in solar physics and helio- seismology for directly obtaining otherwise inaccessible properties (subsurface flows, structures etc.) On the other hand, these analysis techniques also help to examine how realistic the simulations are