The multi-thermal and multi-stranded nature of coronal rain

In this work, we analyse coordinated observations spanning chromospheric, TR and coronal temperatures at very high resolution which reveal essential characteristics of thermally unstable plasmas. Coronal rain is found to be a highly multi-thermal phenomenon with a high degree of co-spatiality in the multi-wavelength emission. EUV darkening and quasi-periodic intensity variations are found to be strongly correlated to coronal rain showers. Progressive cooling of coronal rain is observed, leading to a height dependence of the emission. A fast-slow two-step catastrophic cooling progression is found, which may reflect the transition to optically thick plasma states. The intermittent and clumpy appearance of coronal rain at coronal heights becomes more continuous and persistent at chromospheric heights just before impact, mainly due to a funnel effect from the observed expansion of the magnetic field. Strong density inhomogeneities on spatial scales of 0.2"-0.5" are found, in which TR to chromospheric temperature transition occurs at the lowest detectable scales. The shape of the distribution of coronal rain widths is found to be independent of temperature with peaks close to the resolution limit of each telescope, ranging from 0.2" to 0.8". However we find a sharp increase of clump numbers at the coolest wavelengths and especially at higher resolution, suggesting that the bulk of the rain distribution remains undetected. Rain clumps appear organised in strands in both chromospheric and TR temperatures, suggesting an important role of thermal instability in the shaping of fundamental loop substructure. We further find structure reminiscent of the MHD thermal mode. Rain core densities are estimated to vary between 2x10^{10} cm^{-3} and 2.5x10^{11} cm^{-3} leading to significant downward mass fluxes per loop of 1-5x10^{9} g s^{-1}, suggesting a major role in the chromosphere-corona mass cycle.Comment: Abstract is only short version. See paper for full. Countless pages, figures (and movies, but not included here). Accepted for publication in the Astrophysical Journa

When is a bottleneck a bottleneck?

Bottlenecks, i.e. local reductions of capacity, are one of the most relevant scenarios of traffic systems. The asymmetric simple exclusion process (ASEP) with a defect is a minimal model for such a bottleneck scenario. One crucial question is "What is the critical strength of the defect that is required to create global effects, i.e. traffic jams localized at the defect position". Intuitively one would expect that already an arbitrarily small bottleneck strength leads to global effects in the system, e.g. a reduction of the maximal current. Therefore it came as a surprise when, based on computer simulations, it was claimed that the reaction of the system depends in non-continuous way on the defect strength and weak defects do not have a global influence on the system. Here we reconcile intuition and simulations by showing that indeed the critical defect strength is zero. We discuss the implications for the analysis of empirical and numerical data.Comment: 8 pages, to appear in the proceedings of Traffic and Granular Flow '1

Milk intake and incident stroke and CHD in populations of European descent: a Mendelian randomisation study

We thank all EPIC participants and staff for their contribution to the study. We also thank staff from the EPIC-CVD coordinating centres for sample preparation and data handling. This research has been conducted using the UK Biobank Resource (application number 29916). Data on coronary artery disease have been contributed by CARDIoGRAMplusC4D investigators and have been downloaded from www.CARDIOGRAMPLUSC4D.ORG.I Sluijswas supported by a personal Dr. Dekker postdoctoral grant (2015T019) from the Netherlands Heart Foundation. NGF and FI acknowledge core Medical Research Council Epidemiology Unit support (MC_UU_12015/5) and NGF acknowledges NIHR Biomedical Research Centre Cambridge: Nutrition, Diet, and Lifestyle Research Theme (IS-BRC-1215-20014). The InterAct project was funded by the EU FP6 programme (grant number LSHM_CT_2006_037197) and provided the biomarker data in the sub-cohort that was used in the current study. These analyses were supported by Cancer Research UK (C8221/A19170). The coordination of EPIC is financially supported by the European Commission (DG-SANCO) and the International Agency for Research on Cancer. The national cohorts are supported by Danish Cancer Society (Denmark); German Cancer Aid, German Cancer Research Center (DKFZ), Federal Ministry of Education and Research (BMBF), Deutsche Krebshilfe, Deutsches Krebsforschungszentrum and Federal Ministry of Education and Research (Germany); Associazione Italiana per la Ricerca sul Cancro-AIRC-Italy and National Research Council (Italy); Dutch Ministry of Public Health, Welfare and Sports (VWS), Netherlands Cancer Registry (NKR), LK Research Funds, Dutch Prevention Funds, Dutch ZON (Zorg Onderzoek Nederland), World Cancer Research Fund (WCRF), Statistics Netherlands (The Netherlands); Health Research Fund (FIS) PI13/00061 (EPIC-Granada) and PI13/01162 (EPIC-Murcia), Regional Governments of Andalucia, Asturias, Basque Country, Murcia and Navarra, ISCIII Health Research Funds RD12/0036/0018 (cofounded by FEDER funds/European Regional Development Fund ERDF) (Spain); Swedish Cancer Society, Swedish Research Council and County Councils of Skane and Vasterbotten (Sweden); Cancer Research UK (14136 to EPIC-Norfolk; C570/A16491 and C8221/A19170 for EPIC-Oxford), Medical Research Council (1000143 to EPIC-Norfolk, MR/M012190/1 to EPIC-Oxford) (UK). EPIC-CVD has been supported by the European Commission Framework Programme 7 (HEALTH-F2-2012-279233), the European Research Council (268834), the UK Medical Research Council (MR/L003120/1), the British Heart Foundation (RG13/13/30194 and RG/18/13/33946) and the National Institute for Health Research (Cambridge Biomedical Research Centre at the Cambridge University Hospitals NHS Foundation Trust). The MEGASTROKE project received funding from sources specified at http://www.megastroke.org/acknowledgments.html. L.E.T.V.analysed the data and drafted the manuscript. L. E. T. V., I. S. and Y. T. vdS. had access to all data for this study. L. E. T. V., I. S., Y. T. vdS., S. B., N. G. F., H. F., F. I., T. K. N., F. R., E. W., K. A., C. D., A. P. C., M. B. S., T. Y. N. T. and A. S. B. contributed to study conception, design and interpretation of data. All authors contributed to critical revision of the manuscript and approval of version to be published.Higher milk intake has been associated with a lower stroke risk, but not with risk of CHD. Residual confounding or reverse causation cannot be excluded. Therefore, we estimated the causal association of milk consumption with stroke and CHD risk through instrumental variable (IV) and gene-outcome analyses. IV analysis included 29 328 participants (4611 stroke; 9828 CHD) of the European Prospective Investigation into Cancer and Nutrition (EPIC)-CVD (eight European countries) and European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) case-cohort studies. rs4988235, a lactase persistence (LP) SNP which enables digestion of lactose in adulthood was used as genetic instrument. Intake of milk was first regressed on rs4988235 in a linear regression model. Next, associations of genetically predicted milk consumption with stroke and CHD were estimated using Prentice-weighted Cox regression. Gene-outcome analysis included 777 024 participants (50 804 cases) from MEGASTROKE (including EPIC-CVD), UK Biobank and EPIC-NL for stroke, and 483 966 participants (61 612 cases) from CARDIoGRAM, UK Biobank, EPIC-CVD and EPIC-NL for CHD. In IV analyses, each additional LP allele was associated with a higher intake of milk in EPIC-CVD (beta = 13 center dot 7 g/d; 95 % CI 8 center dot 4, 19 center dot 1) and EPIC-NL (36 center dot 8 g/d; 95 % CI 20 center dot 0, 53 center dot 5). Genetically predicted milk intake was not associated with stroke (HR per 25 g/d 1 center dot 05; 95 % CI 0 center dot 94, 1 center dot 16) or CHD (1 center dot 02; 95 % CI 0 center dot 96, 1 center dot 08). In gene-outcome analyses, there was no association of rs4988235 with risk of stroke (OR 1 center dot 02; 95 % CI 0 center dot 99, 1 center dot 05) or CHD (OR 0 center dot 99; 95 % CI 0 center dot 95, 1 center dot 03). Current Mendelian randomisation analysis does not provide evidence for a causal inverse relationship between milk consumption and stroke or CHD risk.Netherlands Heart Foundation 2015T019UK Research & Innovation (UKRI) Medical Research Council UK (MRC)European Commission MC_UU_12015/5NIHR Biomedical Research Centre Cambridge: Nutrition, Diet, and Lifestyle Research Theme IS-BRC-1215-20014European Commission LSHM_CT_2006_037197Cancer Research UK C8221/A19170European Commission European Commission Joint Research CentreInternational Agency for Research on CancerDanish Cancer SocietyDeutsche Krebshilfe German Cancer Research Center (DKFZ) (Germany)Federal Ministry of Education & Research (BMBF)Deutsche Krebshilfe Deutsches Krebsforschungszentrum (Germany)Federal Ministry of Education & Research (BMBF)Fondazione AIRC per la ricerca sul cancro Consiglio Nazionale delle Ricerche (CNR)Netherlands Government Netherlands GovernmentWorld Cancer Research Fund International (WCRF)Netherlands GovernmentInstituto de Salud Carlos III PI13/00061 PI13/01162Junta de Andalucia Regional Government of Asturias (Spain) Regional Government of Basque Country (Spain) Regional Government of Murcia (Spain) Regional Government of Navarra (Spain)ISCIII Health Research Funds (FEDER funds/European Regional Development Fund ERDF) (Spain) RD12/0036/0018Swedish Cancer Society Swedish Research Council County Council of Skane (Sweden) County Council of Vasterbotten (Sweden)European Commission Framework Programme 7 HEALTH-F2-2012-279233 European Research Council (ERC) European Commission 268834UK Research & Innovation (UKRI) Medical Research Council UK (MRC) MR/L003120/1 British Heart Foundation RG13/13/30194 RG/18/13/33946 National Institute for Health Research (Cambridge Biomedical Research Centre at the Cambridge University Hospitals NHS Foundation Trust) UK Research & Innovation (UKRI) Medical Research Council UK (MRC) 1000143 MR/M012190/1 Cancer Research UK C8221/A19170 14136 C570/A1649

Dissecting bombs and bursts: non-LTE inversions of low-atmosphere reconnection in SST and IRIS observations

Ellerman bombs and UV bursts are transient brightenings that are ubiquitously observed in the lower atmospheres of active and emerging flux regions. Here we present inversion results of SST/CRISP and CHROMIS, as well as IRIS data of such transient events. Combining information from the Mg II h & k, Si IV and Ca II 8542A and Ca II H & K lines, we aim to characterise their temperature and velocity stratification, as well as their magnetic field configuration. We find average temperature enhancements of a few thousand kelvin close to the classical temperature minimum, but localised peak temperatures of up to 10,000-15,000 K from Ca II inversions. Including Mg II generally dampens these temperature enhancements to below 8000 K, while Si IV requires temperatures in excess of 10,000 K at low heights, but may also be reproduced with secondary temperature enhancements of 35,000-60,000 K higher up. However, reproducing Si IV comes at the expense of overestimating the Mg II emission. The line-of-sight velocity maps show clear bi-directional jet signatures and strong correlation with substructure in the intensity images, with slightly larger velocities towards the observer than away. The magnetic field parameters show an enhancement of the horizontal field co-located with the brightenings at similar heights as the temperature increase. We are thus able to largely reproduce the observational properties of Ellerman bombs with UV burst signature with temperature stratifications peaking close to the classical temperature minimum. Correctly modelling the Si IV emission in agreement with all other diagnostics is, however, an outstanding issue. Accounting for resolution differences, fitting localised temperature enhancements and/or performing spatially-coupled inversions is likely necessary to obtain better agreement between all considered diagnostics.Comment: Accepted for publication in Astronomy & Astrophysics. 24 pages, 17 figure

Self-Assembly of Patchy Colloidal Dumbbells

We employ Monte Carlo simulations to investigate the self-assembly of patchy colloidal dumbbells interacting via a modified Kern-Frenkel potential by probing the system concentration and dumbbell shape. We consider dumbbells consisting of one attractive sphere with diameter $\sigma_1$ and one repulsive sphere with diameter $\sigma_2$ and center-to-center distance $d$ between the spheres. For three different size ratios, we study the self-assembled structures for different separations $l = 2d/(\sigma_1+\sigma_2)$ between the two spheres. In particular, we focus on structures that can be assembled from the homogeneous fluid, as these might be of interest in experiments. We use cluster order parameters to classify the shape of the formed structures. When the size of the spheres is almost equal, $q=\sigma_2/\sigma_1=1.035$, we find that, upon increasing $l$, spherical micelles are transformed to elongated micelles and finally to vesicles and bilayers. For size ratio $q=1.25$ we observe a continuously tunable transition from spherical to elongated micelles upon increasing the sphere separation. For size ratio $q=0.95$ we find bilayers and vesicles, plus faceted polyhedra and liquid droplets. Our results identify key parameters to create colloidal vesicles with attractive dumbbells in experiments

The multi-thermal and multi-stranded nature of coronal rain

We analyze coordinated observations of coronal rain in loops, spanning chromospheric, transition region (TR), and coronal temperatures with sub-arcsecond spatial resolution. Coronal rain is found to be a highly multithermal phenomenon with a high degree of co-spatiality in the multi-wavelength emission. EUV darkening and quasi-periodic intensity variations are found to be strongly correlated with coronal rain showers. Progressive cooling of coronal rain is observed, leading to a height dependence of the emission. A fast-slow two-step catastrophic cooling progression is found, which may reflect the transition to optically thick plasma states. The intermittent and clumpy appearance of coronal rain at coronal heights becomes more continuous and persistent at chromospheric heights just before impact, mainly due to a funnel effect from the observed expansion of the magnetic field. Strong density inhomogeneities of 0.″2-0.″5 are found, in which a transition from temperatures of 105 to 104 K occurs. The 0.″2-0.″8 width of the distribution of coronal rain is found to be independent of temperature. The sharp increase in the number of clumps at the coolest temperatures, especially at higher resolution, suggests that the bulk distribution of the rain remains undetected. Rain clumps appear organized in strands in both chromospheric and TR temperatures. We further find structure reminiscent of the magnetohydrodynamic (MHD) thermal mode (also known as entropy mode), thereby suggesting an important role of thermal instability in shaping the basic loop substructure. Rain core densities are estimated to vary between 2 × 1010 and 2.5 × 1011cm−3, leading to significant downward mass fluxes per loop of 1–5 × 109 g s−1, thus suggesting a major role in the chromosphere-corona mass cycle.Publisher PDFPeer reviewe