Geomagnetically Induced Currents in the Irish Power Network during Geomagnetic Storms

Geomagnetically induced currents (GICs) are a well-known terrestrial space weather hazard. They occur in power transmission networks and are known to have adverse effects in both high and mid-latitude countries. Here, we study GICs in the Irish power transmission network (geomagnetic latitude 54.7--58.5$^{\circ}$ N) during five geomagnetic storms (06-07 March 2016, 20-21 December 2015, 17-18 March 2015, 29-31 October 2003 and 13-14 March 1989). We simulate electric fields using a plane wave method together with two ground resistivity models, one of which is derived from magnetotelluric measurements (MT model). We then calculate GICs in the 220, 275 and 400~kV transmission network. During the largest of the storm periods studied, the peak electric field was calculated to be as large as 3.8~V~km\textsuperscript{-1}, with associated GICs of up to 23~A using our MT model. Using our homogenous resistivity model, those peak values were 1.46~V~km\textsuperscript{-1} and 25.8~A. We find that three 400 and 275~kV substations are the most likely locations for the Irish transformers to experience large GICs.Comment: 14 pages, 11 Figures, 4 Table

Racemic Naproxen: A Multidisciplinary Structural and Thermodynamic Comparison with the Enantiopure Form

Following the computational prediction that (<i>RS</i>)-naproxen would be more stable than the therapeutically used and more studied homochiral (<i>S</i>)-naproxen, we performed an interdisciplinary study contrasting the two compounds. The crystal structure of the racemic compound was solved from powder X-ray diffraction data (<i>Pbca</i>) and showed no packing similarity with the homochiral structure (<i>P</i>2₁). The binary melting point phase diagram was constructed to confirm the nature of the racemic species, and differential scanning calorimetric and solubility measurements were used to estimate the enthalpy difference between the crystals (Δ<i>H</i>_{<i>R</i>+<i>S</i>→<i>RS</i>}^cry) to be −1.5 ± 0.3 kJ·mol^–1 at <i>T</i> ∼ 156 °C and −2.4 ± 1.0 kJ·mol^–1 in the range 10–40 °C. A comparison of the different approximations involved in estimating Δ<i>H</i>_{<i>R</i>+<i>S</i>→<i>RS</i>}^cry implied that the difference in the lattice energies overestimated the stability of the (<i>RS</i>) crystal. The naproxen lattice energy landscape confirmed that all the practically important crystal structures have been found and characterized and provided insights into the crystal growth problems of the racemic form. This highlights the complementarity of computational modeling in investigating chiral crystallization