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OPserver: opacities and radiative accelerations on demand

OPserver: opacities and radiative accelerations on demand. C Mendoza (IVIC, Ven) LS Rodríguez (IVIC, Ven) MJ Seaton (UCL, UK) F Delahaye (OPM, France) P Buerger (OSC, USA) E Palacios (UC, Ven) A Bellorín (UCV,Ven) AK Pradhan (OSU, USA)

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OPserver: opacities and radiative accelerations on demand

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  1. OPserver: opacities and radiative accelerations on demand C Mendoza (IVIC, Ven) LS Rodríguez (IVIC, Ven) MJ Seaton (UCL, UK) F Delahaye (OPM, France) P Buerger (OSC, USA) E Palacios (UC, Ven) A Bellorín (UCV,Ven) AK Pradhan (OSU, USA) M Meléndez (USB, Ven) CJ Zeippen (OPM, France) J González (UC/IVIC, Ven) High Accuracy Atomic Physics in Astronomy ITAMP 07/008/2006

  2. e-Science is to do with the exploitation of the Internet as a powerful research environment • Generate, store and analyze large volumes of scientific data • LHC • Virtual observatories • Genomics/proteomics • Perform large-scale modeling and simulations • Nanoscience • Establish and manage dynamic and distributed virtual organizations • Grid

  3. In GRID environments, computing is conceived as an efficient network service with unlimited capabilities Portal GRID

  4. Input Executable Disc Output Scientific computing is mainly carried out under the traditional paradigm Source Compilation

  5. Scientific computing in grid environments requires a more modern scheme: data-based centered Input DBMS Executable Output Disc

  6. Web server Web client Supercomputer CGI-scripts Executable 1/2 Executable 1/2 HTML Java portlet Java application Disc Disc Disc Scientific computing in grid environments is markedly distributed

  7. The standard model of the Sun interior has recently given rise to an intense polemic • Helioseismology • R(obs) = 0.713 0.001 R☼ • R(theory) = 0.713 R☼ (Basu & Antia 1997) • Chemical abundance • Z/H = 0.0229 (Grevesse & Sauval, 1998) • Z/H = 0.0176 (Asplund et al. 2004) • R(theory) = 0.726 R☼ • Opacities • OP: recently revised (Badnell et al. 2005) • OPAL and OP in 2.5% accord • The impact of the revised abundances has been extensively discussed by Bahcall & et al. (2005)

  8. Detailed stellar models are now including effects due to microscopic diffusion • Microscopic diffusion: • Radiative levitation • Gravitational • Thermal diffusion • It affects: • Internal and thermal structures of star • Convection zone depth • Pulsations • Anomalies in superficial abundances

  9. Computing time of RMOs and RAs depends on the disk reading of monochromatic opacities (1Gb) • For a chemical mixture with relative abundances fi, the Rosseland mean opacity (RMO) is given by •  • 1/kR = mF(u)/s(u) du •  • where u=hn/kT • F(u) = [15/p4] u4 exp(-u)/[1 – exp(-u)]2 • and the opacity cross section of the mixture • s(u) =  fisi(u) • is the sum of the monochromatic opacities of each ion.

  10. Computing time of RMOs and RAs depends on the disk reading of monochromatic opacities (1Gb) • The radiative acceleration for the ith element is • grad = m kRgi F/(cmi) • where • F = pB(Teff)(R☼/r)2 con B(T) = 2(pkT)4/(15c2h3). • The non-dimensional parameter •  • gi =  simta/s du •  • depends on the momentum transfer cross section • simta = si(u) [1- exp(-u)] – ai(u) .

  11. start RA start RMO mixv.in acc.in Mono 1 Gb mixv accv acc.xx 470 Kb mixv.xx 85 Kb Stage 1 accfit opfit opfit.in accfit.in Stage 2 opfit.xx accfit.xx end RMO end RA

  12. OPserver exploits the client-server network architecture • Opacity codes in OPCD (Seaton 2005) are restructured in a client-server network architecture • User interaction is either through a web page or a linkable a subroutine library (OPlibrary) • The RMOs and RAs are computed with the monochromatic opacities always loaded in RAM • Remote calls are addressed through the HTTP protocol (URLs) • Codes have been parallelized (OpenMP)

  13. OSC Web server Supercomputer OPlibrary mono Web client OPlibrary Modelling code Modelling code A B C

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