Talk: Magnetar Dynamics & Grav. Waves

Kostas Kokkotas (Tübingen)

  • Magnetars exhibit regular gamma-ray flares that are preceded by star quakes or glitches in the pulsations.  The largest flares have L ~ 10^47 erg/s (3 since 1979).
  • No natural explanation for (1) sudden stop of activity P ~ 12 sec and (2) AXP-SNR association but no SGR-SNR association
  • Thompson & Duncan (1990’s) – developed a fireball model that erupts from the NS surface to explain these largest bursts.
  • Can QPOs be explained by global Alfvèn waves?  (see KK publications)
  • NS models, using perturbation theory, with crust and B-fields to predict QPO frequencies.  No crust oscillations at B > 4 x 10^14 G.
  • Gravitational wave amplitudes are unknown and must be calculated with simulations (3D GRMHD).
  • Simulation of B-field instability (Lasky et al. 2011, ApJL) and prediction for GW (Zink et al. 2011)

GPU Meeting (20 Sept 2011)

Matt Kinsey: Porting the 2D Wave Equation to the GPU
  • Optimal number of threads per block is 32*n-1, where n is an integer.  The best performance in the example shown was 63 threads per block.
  • Minimum number of blocks per grid is 32, according to the user’s guide.
  • Every time a kernel is called, the memory needs to be pushed from the CPU to the GPU.  Thus it is optimal to minimize the kernel calls.
  • In the 2D wave equation problem, Matt utilized texture memory to reduce the number of kernels to one.  The memory is indexed in a space-filling curve.  This results in better cache locality.
  • With texture memory, one can take advantage of built-in linear interpolation and boundary conditions.  Texture memory can be addressed in 1D, 2D, and 3D.