A 2015 International Geomagnetic Reference Field (IGRF) candidate model based on <i>Swarm’s</i> experimental absolute magnetometer vector mode data

International audienceEach of the three satellites of the European Space Agency Swarm mission carries an absolute scalar magnetometer (ASM) that provides the nominal 1-Hz scalar data of the mission for both science and calibration purposes. These ASM instruments, however, also deliver autonomous 1-Hz experimental vector data. Here, we report on how ASM-only scalar and vector data from the Alpha and Bravo satellites between November 29, 2013 (a week after launch) and September 25, 2014 (for on-time delivery of the model on October 1, 2014) could be used to build a very valuable candidate model for the 2015.0 International Geomagnetic Reference Field (IGRF). A parent model was first computed, describing the geomagnetic field of internal origin up to degree and order 40 in a spherical harmonic representation and including a constant secular variation up to degree and order 8. This model was next simply forwarded to epoch 2015.0 and truncated at degree and order 13. The resulting ASM-only 2015.0 IGRF candidate model is compared to analogous models derived from the mission's nominal data and to the now-published final 2015.0 IGRF model. Differences among models mainly highlight uncertainties enhanced by the limited geographical distribution of the selected data set (essentially due to a lack of availability of data at high northern latitude satisfying nighttime conditions at the end of the time period considered). These appear to be comparable to differences classically observed among IGRF candidate models. These positive results led the ASM-only 2015.0 IGRF candidate model to contribute to the construction of the final 2015.0 IGRF model

International Geomagnetic Reference Field: the 12th generation

The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth’s magnetic fiel

A new ligand for chromium-catalyzed polymerization of ethylene at room temperature. Crystal structures of the lignads and chromium complex

International audienc

Acetyl-hydroxy-fulvene: A new ligand for chromium-catalyzed polymerization of ethylene at room temperature. Crystal structures of the ligands and chromium complex

International audienceIn the field of transition metal catalysts for olefin polymerization, the discovery of new chelating ligands has attracted significant interest. This paper reports on the polymerization of ethylene with new chromium based catalysts containing an acetyl-hydroxy-fulvene ligand. A parallel method was applied to screen eleven metal salts versus two different functionalized fulvene ligands. A direct visual analysis showed solid PE formation only in vials containing a chromium salt after 1 h of polymerization at 35 °C and 15 bar. This preliminary screening was followed by optimization studies to obtain high activities (up to 5 tPE/(mol·h)). ORTEP structures of the corresponding ligands and of the best catalysts were reporte

Efficient enantioselective hydrosilylation of ketones catalyzed by air stable copper fluoride-phosphine complexes.

[reaction: see text] Copper(II) fluoride-chiral diphosphine systems catalyze the hydrosilylation of several ketones with moderate to excellent enantioselectivities. An oxygen acceleration effect was observed and led to a practical protocol with low catalyst loading

Air-accelerated enantioselective hydrosilylation of ketones catalyzed by copper(I) fluoride-diphosphine complexes: Investigations of the effects of temperature and ligand structure

The fluorotris(triphenylphosphine)copper(I)-bis(methanol) complex-chiral diphosphine system catalyzes the hydrosilylation of several alkyl aryl ketones with moderate to excellent enantioselectivity. An oxygen acceleration effect was observed and led to a practical protocol with low catalyst loading. Optimizations of enantioselectivities (< 95%) and catalytic ratio (< 0.05 mol%) were obtained with bulky Ar-MeO-BIPHEP ligands