Relationship between Interplanetary Conditions and Changes in the Geomagnetic Field to Understand the Causes of Geomagnetically Induced Currents

Geomagnetically Induced Currents (GICs) are electrical currents induced in ground-level conductive networks, like power lines and pipelines, which can cause costly damage to infrastructure. GICs are induced in response to fast changes in the geomagnetic field (GMF) according to Faraday’s Law of Electromagnetic Induction. The purpose of this study was to identify the parameters of the solar wind and interplanetary shocks which are most strongly correlated with large, fast changes in the magnitude of the GMF. GMF data is 1-min averaged time series of mid- and high-latitude magnetometer measurements in the Sym/H and AL indices, respectively. For solar wind data, I used an existing database of fast-forward interplanetary shocks compiled from measurements made by the WIND spacecraft. I performed t-tests, and created linear fits to determine which parameter(s) are likely responsible for large 1-min changes in the Sym/H and AL indices. Large changes in Sym/H are most strongly correlated with speed jump at the shock and the change in the square root of dynamic pressure and large changes in AL with speed jump at the shock. To determine the causes of events with larger 1-min changes than the fit, I created a subset of shocks which follow the trend with the same distribution as the outliers to find causes for the outliers. This revealed that faster shock and stronger upstream magnetic field are associated with stronger GMF changes

The interactive effects of arbuscular mycorrhiza and plant growth-promoting rhizobacteria synergistically enhance host plant defences against pathogens

Belowground interactions between plant roots, mycorrhizal fungi and plant growth-promoting rhizobacteria (PGPR) can improve plant health via enhanced nutrient acquisition and priming of the plant immune system. Two wheat cultivars differing in their ability to form mycorrhiza were (co)inoculated with the mycorrhizal fungus Rhizophagus irregularis and the rhizobacterial strain Pseudomonas putida KT2440. The cultivar with high mycorrhizal compatibility supported higher levels of rhizobacterial colonization than the low compatibility cultivar. Those levels were augmented by mycorrhizal infection. Conversely, rhizobacterial colonization of the low compatibility cultivar was reduced by mycorrhizal arbuscule formation. Single inoculations with R. irregularis or P. putida had differential growth effects on both cultivars. Furthermore, while both cultivars developed systemic priming of chitosan-induced callose after single inoculations with R. irregularis or P. putida, only the cultivar with high mycorrhizal compatibility showed a synergistic increase in callose responsiveness following co-inoculation with both microbes. Our results show that multilateral interactions between roots, mycorrhizal fungi and PGPR can have synergistic effects on growth and systemic priming of wheat

The 1930s as black mirror: Visions of historical repetition in the global financial press, 2007-2009

Media coverage of the recent financial crisis has referred extensively to various past crises, and in particular to the events of the 1930s. This article suggests that the idea of the Great Depression has effectively come to function as a kind of historical ‘black mirror’ – a quasi-object within which conjuncture and historical representation interact to produce an image of capitalist history itself. Focusing on the journalistic output of four key financial publications, I trace how portrayals of the 1930s have evolved over the course of the crisis. I find that while the 1930s are frequently and consistently invoked in ways that purport to reveal the historicity of the crisis, these representations produce an oscillation between different visions of historical repetition, which in turn underpin competing interpretations of the crisis as it unfolds. In so doing, I argue, appeals to the 1930s have simultaneously served to conceal and disclose the constitutive relation of historical imagination to historical process – a double move that has had the paradoxical effect of both securing and undermining the reproduction of finance capitalism as we have come to know it

Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluid?

Hypotheses for the formation of many types of hydrothermal ore deposits often involve the direct contribution of magma-related fluids (e.g., Cu–Mo–Au porphyries) or their superimposition on barren hydrothermal cells (e.g., volcanic-hosted massive sulfide deposits). However, the chemical and phase compositions of such fluids remain largely unknown. We report preliminary results of a comprehensive study of fluid bubbles trapped inside glassy melt inclusions in primitive olivine phenocrysts and pillow-rim glasses from basaltic magmas from different tectonic environments, including mid-ocean ridges (Macquarie Island, SW Pacific and Mid-Atlantic Ridge 43°N Fracture Zone), ocean islands (Hawaii) and a variety of modern and ancient backarc–island arc settings (eastern Manus Basin, Okinawa and Vanuatu Troughs, Troodos, New Caledonia and Hunter Ridge–Hunter Fracture Zone). Fluid bubbles from all localities, studied using electron microscopy with EDS and laser Raman spectroscopy, are composed of CO2-(±H2O±sulfur)-bearing vapor and contain significant amounts of amorphous (Na–K–Ca–Fe alumino-silicates and dissorded carbon) and crystalline phases. The crystals are represented mainly by carbonates (magnesite, calcite, ankerite, dolomite, siderite, nahcolite and rhodochrosite), sulfates (anhydrite, gypsum, barite and anglesite), and sulfides (pyrite, arsenopyrite, chalcopyrite and marcasite), though other minerals (brukite, apatite, halite, clinoenstatite, kalsilite, nepheline, amphibole and mica) may occur as well. We argue that chemical components (e.g., C, H, S, Cl, Si, Al, Na, K, Fe, Mn, Cr, Ca, Mg, Ba, Pb and Cu) that later formed precipitates in fluid bubbles were originally dissolved in the magmatic fluid, and were not supplied by host glasses or phenocrysts after entrapment. Magma-related fluid rich in dissolved metals and other non-volatile elements may be a potential precursor to ore-forming solutions