Transcript HMI08.ppt
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 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 Simulated data are being ingested into the new SDO JSOC database • Website http://sha.stanford.edu/stein_sim (some info) • Contact Bob Stein [email protected] (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 helioseismology 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