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A suite of application benchmarks, designed to be broadly representative of UK HPC usage, has been developed to stress a broad range of architectural features of large scale parallel HPC resources. A generic methodology to investigate application performance and scaling characteristics has been defined, resulting in a detailed understanding of the performance of these applications. This methodology is transferable to other applications and systems: it is of practical value to developers and users who are aiming for optimal utilisation of HPC resources. An understanding of the performance characteristics of a range of large-scale HPC resources has been obtained using low-level synthetic benchmarks. A relatively simple, qualitative mechanism to assess and predict application performance on current and future architectures using synthetic benchmark results together with application performance analysis results is explored.

Resonance lines of highly ionized H and He-like ions and their associated sa- tellite lines are used to determine the electron temperature and the transient state of the plasma in solar flares. The intensity ratio of the satellite lines l~~nll-ls2~nL to the resonance line ls2-1s2p has been calculated for the n = 2, 3 and 4 shells of Fe XXIV. The results have enabled the identification of many lines in the only available high resolution solar flare iron spectrum and give a good estimate of the spectral intensity in the resonance line by evaluating the contribution due to the blending of the satellites with n 2 3. I. SATELLITE LINES IN THE SPECTRA OF H-LIKE AND like and He-like resonance lines and a number of He-LIKE IONS. associated satellites. The prominent satellites Resonance lines of highly ionized H-like have n = 2 and are well separated from the parent and He-like ions and their associated satellites resonance line, those with n = 3 lie closer, while can be used to calculate electron temperature and satellites with n z 4 are usually blended with the the transient state of the plasma, both of which resonance line. As first suggested by Gabriel et are important in the study of solar flare proces- al. 117, the satellite lines are formed by the me

Effective collision strengths are presented for the forbidden line 1s2 1S0-1s2s 3S1 in He-like ions taking account of the effect of resonances and their radiative decay. Results are obtained using the quantum defect theory developed by Gailitis (1963) and Seaton (1969) and are applied to the ions O VII, Mg XI, Ca XIX and Fe XXV. Excitation rates are given in LSJ coupling for a temperature range where these ions are abundant and they are compared, where possible, with previous results. The results indicate that the contribution of the resonances to the direct collision strength is lower than 20% for the temperature range of interest.

For pt.I see ibid., vol.10, p.2639 (1977). Elastic scattering of electrons by atoms is considered in the approximation of using polarised atom states, which gives a system of coupled differential equations. Solutions for large r(r>rN) are obtained using the method of the previous paper in this series. Solutions in the finite range 0

Wavelengths and atomic parameters for both dielectronic and inner-shell satellite lines of the type 1s2nl-1s2l'nl have been calculated for O VI. The atomic data for these satellite lines with n=2 were calculated in a multiconfiguration intermediate-coupling scheme and are compared with previous results. The fine-structure splitting is also compared with previous detailed calculations. Calculations for the dielectronic satellite lines with n=3, 4 and 5 have been performed in a multiconfiguration LS coupling scheme. The intensities of the n=6 satellites are derived from these data and thus an estimate of the contribution of the dielectronic satellites to the resonance line is obtained. New calculations for the excitation rates for both the inner-shell satellites, excited from 1s22s and 1s22p, and the resonance line 1s2 1S-1s2p 1P of O VII are also presented. The intercombination and forbidden lines 1s2-1s2p 3P, 3S are not considered.

High resolution spectra of the Ly ..cap alpha../sub 1/ and Ly ..cap alpha../sub 2/ lines of hydrogenlike titanium, TiXXII, and the associated dielectronic satellites which are due to transitions 1snl-2pnl with n greater than or equal to 2, have been observed from tokamak discharges with auxiliary ion cyclotron heating (ICRH) with central electron temperatures of 2 keV and central electron densities of 8 x 10/sup 13/ cm/sup -3/ on the Princeton Large Torus (PLT). The data have been used for a detailed comparison with theoretical predictions based on the Z - expansion method and Hartree - Fock calculations. The results obtained with the Z - expansion method are in excellent agreement with the observed spectral data except for minor discrepancies between the theoretical and experimental wavelengths of 0.0003 A for the n = 2 satellites and of 0.0001 A for the separation of the Ly ..cap alpha../sub 1/ and Ly ..cap alpha../sub 2/ lines. Very good agreement with the experimental data is also obtained for the results from the Hartree - Fock calculations though somewhat larger discrepancies (approx. = 0.0009 A) exist between experimental and theoretical wavelengths which are systematically too small. The observed spectra are used for diagnosis ofmore » the central ion and electron temperatures of the PLT discharges and for a measurement of the dielectronic recombination rate coefficient of TiXXII.« less

An analysis of Mg XI spectra from two non-flaring solar active regions is presented; the electron temperature and ion abundances have been determined.

The effect on stratospheric temperature of changing ozone is investigated by comparing two 5-member ensembles of 20-year Unified Model transient runs, one with a linear trend in ozone and one without. A significant stratospheric mean temperature trend of -0.17 K/ decade is attributed to ozone depletion. It is found that, although increasing the ensemble size to 20 members would have considerable benefits, increasing the ensemble size further would not dramatically improve confidence in the results. The timeslice approach to climate change modeling is found to produce similar temperature trends to the transient approach for this experiment. Copyright 2004 by the American Geophysical Union.

High-resolution solar spectra of the Mg XI 1s2 1S0-1s2p 1P1 resonance line at 9.169 A and the associated nearby satellite lines obtained from two rocket-borne crystal spectrometer measurements are presented. Comparisons with two independent sets of theoretical calculations for the 1s2nl-1s2pnl dielectronic satellite lines with n = 3-7 indicate electron temperatures of 4-4.5 million K. Measured line widths indicate either that the ion temperature exceeds the electron temperature by about a million K or that about 28 km/s of turbulence is present.