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Journal articleChen CHK, Howes GG, Bonnell JW, et al., 2013, , AIP Conference Proceedings, Vol: 1539, Pages: 143-146
We motivate the importance of studying kinetic scale turbulence forunderstanding the macroscopic properties of the heliosphere, such as theheating of the solar wind. We then discuss the technique by which kinetic scaledensity fluctuations can be measured using the spacecraft potential, includinga calculation of the timescale for the spacecraft potential to react to thedensity changes. Finally, we compare the shape of the density spectrum at ionscales to theoretical predictions based on a cascade model for kineticturbulence. We conclude that the shape of the spectrum, including the ion scaleflattening, can be captured by the sum of passive density fluctuations at largescales and kinetic Alfven wave turbulence at small scales.
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Journal articleMatteini L, Hellinger P, Goldstein BE, et al., 2013, , Journal of Geophysical Research: Space Physics, Vol: 118, Pages: 2771-2782, ISSN: 2169-9380
<jats:p>An analysis of ion non鈥恡hermal properties in the fast solar wind based on Ulysses data is reported. The radial evolution of the main proton moments (density, temperature, and drift velocities) and their empirical correlations with other plasma parameters are investigated in detail and compared with theoretical expectations. The stability of the plasma is studied against different ion kinetic instabilities driven by ion temperature anisotropies and differential velocities, focusing on the identification of possible signatures of relevant instabilities in the observed core鈥恇eam structure of proton distributions. The temperature anisotropy of the total proton distribution appears to be constrained by fire hose instabilities, in agreement with previous studies, while if considered separately, beam and core populations exhibit opposite anisotropies, with core protons characterized by perpendicular temperatures larger than the parallel ones, possibly (marginally) unstable for ion鈥恈yclotron instability. The evolution with distance of the drift velocity between the secondary population and the main core is found to be nonadiabatic, leading to the identification of a marginal stability path of a magnetosonic ion鈥恇eam instability. As a conclusion, we find that a large fraction of the proton distributions observed by Ulysses display signatures of either a beam or a fire hose instability, suggesting that such kinetic processes play an important role in regulating the solar wind thermal energetics during the plasma expansion.</jats:p>
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Journal articleProvan G, Cowley SWH, Sandhu J, et al., 2013, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 3243-3264
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- Citations: 59
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Journal articleBalogh A, Erdos G, 2013, , SPACE SCIENCE REVIEWS, Vol: 176, Pages: 177-215, ISSN: 0038-6308
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- Citations: 30
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Journal articleRay LC, Galand M, Delamere PA, et al., 2013, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 3214-3222, ISSN: 2169-9380
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- Citations: 15
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Journal articleEastwood JP, Phan TD, Drake JF, et al., 2013, , PHYSICAL REVIEW LETTERS, Vol: 110, ISSN: 0031-9007
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- Citations: 88
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Journal articleNaik V, Voulgarakis A, Fiore AM, et al., 2013, , Atmospheric Chemistry and Physics, Vol: 13, Pages: 5277-5298
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Journal articleChan NLA, Brindley HE, Ekins-Daukes NJ, 2013, , Progress in Photovoltaics, Vol: 22, Pages: 1080-1095, ISSN: 1099-159X
The performance of concentrator photovoltaic systems can be characterised by the power output under reference conditions and the output energy yield under realistic solar illumination. For a range of locations, the frequency distribution of individual atmospheric parameters and their quantitative impact on power output of a concentrator photovoltaic system have been evaluated, with aerosols shown to have a substantial impact on performance at many sites. Limited knowledge of atmospheric parameters results in a difference of up to 75% in simulated energy yield over an annual period and up to 75% deviation in the expected levelised cost of energy.
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Journal articleLiu YD, Luhmann JG, Lugaz N, et al., 2013, , ASTROPHYSICAL JOURNAL, Vol: 769, ISSN: 0004-637X
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- Citations: 119
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Journal articleVoulgarakis A, Shindell DT, Faluvegi G, 2013, , Atmospheric Chemistry and Physics, Vol: 13, Pages: 4907-4916
<jats:p>Abstract. Coupling between the stratosphere and the troposphere allows changes in stratospheric ozone abundances to affect tropospheric chemistry. Large-scale effects from such changes on chemically produced tropospheric aerosols have not been systematically examined in past studies. We use a composition-climate model to investigate potential past and future impacts of changes in stratospheric ozone depleting substances (ODS) on tropospheric oxidants and sulfate aerosols. In most experiments, we find significant responses in tropospheric photolysis and oxidants, with small but significant effects on methane radiative forcing. The response of sulfate aerosols is sizeable when examining the effect of increasing future nitrous oxide (N2O) emissions. We also find that without the regulation of chlorofluorocarbons (CFCs) through the Montreal Protocol, sulfate aerosols could have increased by 2050 by a comparable amount to the decreases predicted due to relatively stringent sulfur emissions controls. The individual historical radiative forcings of CFCs and N2O through their indirect effects on methane (−22.6 mW m−2 for CFCs and −6.7 mW m−2 for N2O) and sulfate aerosols (−3.0 mW m−2 for CFCs and +6.5 mW m−2 for N2O when considering the direct aerosol effect) discussed here are non-negligible when compared to known historical ODS forcing. Our results stress the importance of accounting for stratosphere-troposphere, gas-aerosol and composition-climate interactions when investigating the effects of changing emissions on atmospheric composition and climate.</jats:p>
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Journal articleDhomse SS, Chipperfield MP, Feng W, et al., 2013,
<jats:p>Abstract. Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (1996–2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O3 using three different solar flux datasets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies from all solar flux datasets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere due to changes in stratospheric dynamics. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux datasets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3 changes during 2001–2010.</jats:p>
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Journal articleCeppi P, Hartmann DL, 2013, , Journal of Climate, Vol: 26, Pages: 3450-3465, ISSN: 0894-8755
A strong correlation between the speed of the eddy-driven jet and the width of the Hadley cell is found to exist in the Southern Hemisphere, both in reanalysis data and in twenty-first-century integrations from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report multimodel archive. Analysis of the space–time spectra of eddy momentum flux reveals that variations in eddy-driven jet speed are related to changes in the mean phase speed of midlatitude eddies. An increase in eddy phase speeds induces a poleward shift of the critical latitudes and a poleward expansion of the region of subtropical wave breaking. The associated changes in eddy momentum flux convergence are balanced by anomalous meridional winds consistent with a wider Hadley cell. At the same time, faster eddies are also associated with a strengthened poleward eddy momentum flux, sustaining a stronger westerly jet in midlatitudes. The proposed mechanism is consistent with the seasonal dependence of the interannual variability of the Hadley cell width and appears to explain at least part of the projected twenty-first-century trends.
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Journal articleBranduardi-Raymont G, Ford PG, Hansen KC, et al., 2013, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 2145-2156, ISSN: 2169-9380
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- Citations: 12
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Journal articleAndres N, Gomez DO, Bertucci C, et al., 2013, , PLANETARY AND SPACE SCIENCE, Vol: 79-80, Pages: 64-75, ISSN: 0032-0633
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- Citations: 23
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Journal articleZhong J, Pu ZY, Dunlop MW, et al., 2013, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 1904-1911, ISSN: 2169-9380
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- Citations: 46
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Journal articleBowman KW, Shindell DT, Worden HM, et al., 2013, , Atmospheric Chemistry and Physics, Vol: 13, Pages: 4057-4072
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Journal articleSimon S, van Treeck SC, Wennmacher A, et al., 2013, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 1679-1699, ISSN: 2169-9380
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- Citations: 34
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Journal articleSergis N, Jackman CM, Masters A, et al., 2013, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 1620-1634, ISSN: 2169-9380
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- Citations: 38
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Journal articleMessori G, Czaja A, 2013, , QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Vol: 139, Pages: 999-1008, ISSN: 0035-9009
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- Citations: 26
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Journal articleHellinger P, Tr谩vn铆膷ek PM, 艩tver谩k 艩, et al., 2013, , Journal of Geophysical Research: Space Physics, Vol: 118, Pages: 1351-1365, ISSN: 2169-9380
<jats:p>The proton thermal energetics in the slow solar wind between 0.3 and 1 AU is reinvestigated using the Helios 1 and 2 data, complementing a similar analysis for the fast solar wind [Hellinger et al., 2011]. The results for slow and fast solar winds are compared and discussed in the context of previous results. Protons need to be heated in the perpendicular direction with respect to the ambient magnetic field from 0.3 to 1 AU. In the parallel direction, protons need to be cooled at 0.3 AU, with a cooling rate comparable to the corresponding perpendicular heating rate; between 0.3 and 1 AU, the required cooling rate decreases until a transition to heating occurs: by 1 AU the protons require parallel heating, with a heating rate comparable to that required to sustain the perpendicular temperature. The heating/cooling rates (per unit volume) in the fast and slow solar winds are proportional to the ratio between the proton kinetic energy and the expansion time. On average, the protons need to be heated and the necessary heating rates are comparable to the energy cascade rate of the magnetohydrodynamic turbulence estimated from the stationary Kolmogorov鈥怸aglom law at 1 AU; however, in the expanding solar wind, the stationarity assumption for this law is questionable. The turbulent energy cascade may explain the average proton energetics (although the stationarity assumption needs to be justified) but the parallel cooling is likely related to microinstabilities connected with the structure of the proton velocity distribution function. This is supported by linear analysis based on observed data and by results of numerical simulations.</jats:p>
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Journal articleGrasset O, Dougherty MK, Coustenis A, et al., 2013, , PLANETARY AND SPACE SCIENCE, Vol: 78, Pages: 1-21, ISSN: 0032-0633
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- Citations: 548
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Journal articleZhong W, Haigh JD, 2013, , WEATHER, Vol: 68, Pages: 100-105, ISSN: 0043-1656
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- Citations: 58
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Journal articleBadman SV, Masters A, Hasegawa H, et al., 2013, , GEOPHYSICAL RESEARCH LETTERS, Vol: 40, Pages: 1027-1031, ISSN: 0094-8276
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- Citations: 73
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Journal articleCoustenis A, Atreya S, Castillo J, et al., 2013, , PLANETARY AND SPACE SCIENCE, Vol: 77, Pages: 1-2, ISSN: 0032-0633
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- Citations: 1
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Journal articleVigren E, Galand M, Yelle RV, et al., 2013, , ICARUS, Vol: 223, Pages: 234-251, ISSN: 0019-1035
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- Citations: 36
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Journal articleMasters A, Stawarz L, Fujimoto M, et al., 2013, , NATURE PHYSICS, Vol: 9, Pages: 164-167, ISSN: 1745-2473
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- Citations: 77
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Journal articleLavvas P, Yelle RV, Koskinen T, et al., 2013, , PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 110, Pages: 2729-2734, ISSN: 0027-8424
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- Citations: 122
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Journal articleMatteini L, Landi S, Velli M, et al., 2013, , The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 763, ISSN: 0004-637X
We investigate the role of kinetic instabilities driven by a proton anisotropy on the onset of magnetic reconnection by means of two-dimensional hybrid simulations. The collisionless tearing of a current sheet is studied in the presence of a proton temperature anisotropy in the surrounding plasma. Our results confirm that anisotropic protons within the current sheet region can significantly enhance/stabilize the tearing instability of the current. Moreover, fluctuations associated with linear instabilities excited by large proton temperature anisotropies can significantly influence the stability of the plasma and perturb the current sheets, triggering the tearing instability. We find that such a complex coupling leads to a faster tearing evolution in the $T_\perp >T_\Vert$ regime when an ion-cyclotron instability is generated by the anisotropic proton distribution functions. On the contrary, in the presence of the opposite anisotropy, fire-hose fluctuations excited by the unstable background protons with $T_\Vert <T_\perp$ are not able to efficiently destabilize current sheets, which remain stable for a long time after fire-hose saturation. We discuss possible influences of this novel coupling on the solar wind and heliospheric plasma dynamics.
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Journal articleShi QQ, Zong Q-G, Fu SY, et al., 2013, , NATURE COMMUNICATIONS, Vol: 4, ISSN: 2041-1723
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- Citations: 81
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Journal articleCargill P, 2013, , NATURE, Vol: 493, Pages: 485-486, ISSN: 0028-0836
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- Citations: 10
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