Numerical three‐dimensional magnetohydrodynamic models are capable of predicting large‐scale solar wind structures at Earth, provided that appropriate time‐dependent boundary conditions are specified near the Sun. Since knowledge of such conditions is at present insufficient to directly drive the models, various approximations are used. In this paper, we introduce the main features and approximations of a numerical model where (1) the ambient solar wind is derived from coronal models utilizing photospheric magnetic field observations and (2) transient disturbances are derived from geometrical and kinematic fitting of coronagraph observations of coronal mass ejections (CMEs). We have chosen the well‐defined halo‐CME event of 12 May 1997 as our initial event because it is characterized by a relatively quiet solar and interplanetary background into which the ejecta was launched. The numerical simulation has enabled us to predict the arrival of the shock and ejecta and provided us with a global picture of transient disturbance interacting with a moderately fast solar wind stream.

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The electrochemical method of combining N2 and H2O to produce ammonia (i.e., the electrochemical nitrogen reduction reaction [E‐NRR]) continues to draw attention as it is both environmentally friendly and well suited for a progressively distributed farm economy. Despite the multitude of recent works on the E‐NRR, further progress in this field faces a bottleneck. On the one hand, despite the extensive exploration and trial‐and‐error evaluation of E‐NRR catalysts, no study has stood out to become the stage protagonist. On the other hand, the current level of ammonia production (microgram‐scale) is an almost insurmountable obstacle for its qualitative and quantitative determination, hindering the discrimination between true activity and contamination. Herein i) the popular theory and mechanism of the NRR are introduced; ii) a comprehensive summary of the recent progress in the field of the E‐NRR and related catalysts is provided; iii) the operational procedures of the E‐NRR are addressed, including the acquisition of key metrics, the challenges faced, and the most suitable solutions; iv) the guiding principles and standardized recommendations for the E‐NRR are emphasized and future research directions and prospects are provided.

WS2 nanodots were prepared by liquid-phase exfoliation of bulk WS2 crystals in surfactant aqueous solution with the aid of ultrasonication. Their behaviors on catalyzing hydrogen evolution reaction (HER) were investigated after drop-casting them onto a glass carbon electrode. On the basis of the optical and electron characterizations, the nanodots were identified with a high concentration of octahedral phase of WS2 that showed better catalysis properties than the hexagonal WS2. From the polarization curve, the Tafel slope was estimated to be 51 mV per decade and the onset potential was 90 mV, indicating good catalytic performance of such nanodots. Our results suggest that surfactant-mediated exfoliation is an environmentally benign method to synthesize WS2 nanodots for improved catalyzing HER.

In this paper, ten CME events viewed by the STEREO twin spacecraft are analyzed to study the deflections of CMEs during their propagation in the corona. Based on the three-dimensional information of the CMEs derived by the graduated cylindrical shell (GCS) model [Thernisien et al., 2006], it is found that the propagation directions of eight CMEs had changed. By applying the theoretical method proposed by Shen et al. [2011] to all the CMEs, we found that the deflections are consistent, in strength and direction, with the gradient of the magnetic energy density. There is a positive correlation between the deflection rate and the strength of the magnetic energy density gradient and a weak anti-correlation between the deflection rate and the CME speed. Our results suggest that the deflections of CMEs are mainly controlled by the background magnetic field and can be quantitatively described by the magnetic energy density gradient (MEDG) model.Comment: 19 pages, 20 figure

A new model of the coronal and interplanetary magnetic field can predict both the interplanetary magnetic field strength and its polarity from measurements of the photospheric magnetic field. The model includes the effects of the large‐scale horizontal electric currents flowing in the inner corona, of the warped heliospheric current sheet in the upper corona, and of volume currents flowing in the region where the solar wind plasma totally controls the magnetic field. The model matches the MHD solution for a simple dipole test case better than earlier source surface and current sheet models. The strength and polarity of the radial interplanetary magnetic field component predicted for quiet time samples in each year from 1977 to 1986 agree with observations made near the Earth's orbit better than the hybrid MHD‐source surface model (Wang and Sheeley, 1988). The results raise the question of whether coronal holes are the only solar source of the interplanetary magnetic field in the solar wind. If some interplanetary flux originates outside coronal holes, the model can match the observed field using the accepted 1.8 saturation correction factor for λ5250 Å magnetograph observations. Requiring open flux to come exclusively from coronal holes requires an additional factor of two.

Amorphous carbon supported MoS₂, which was elaborately prepared by using a facile hydrothermal method followed by annealing, is first employed as a catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a preparation strategy, by which MoS₂ and carbon materials could be formed in situ and simultaneously. The MoS₂ nanosheets are vertically formed on the carbon nanosphere, as illustrated in the scanning electron micrograph. The unique morphology can expose abundant edges of the MoS₂ layer as active sites for the HER, while the underlying amorphous carbon effectively improves the conductivity. By means of employing amorphous carbon as a substrate, an optimized catalyst was developed, which exhibited enhanced catalytic activity for the electrocatalytic HER with an onset potential as low as 80 mV, extremely large cathodic current density and excellent stability. Notably, a Tafel slope of 40 mV per decade was measured, which exceeds by far the activity of previous MoS₂ catalysts and suggests the Volmer-Heyrovsky-mechanism for the MoS₂-catalyzed HER.

The photospheric magnetic field in the Sun's polar region is not well observed compared to the low-latitude regions. Data are periodically missing due to the Sun's tilt angle, and the noise level is high due to the projection effect on the line-of-sight (LOS) measurement. However, the large-scale characteristics of the polar magnetic field data are known to be important for global modeling. This report describes a new method for interpolating the photospheric field in polar regions that has been tested on MDI synoptic maps (1996 -2009). This technique, based on a two-dimensional spatial/temporal interpolation and a simple version of the flux transport model, uses a multi-year series of well-observed, smoothed north (south) pole observations from each September (March) to interpolate for missing pixels at any time of interest. It is refined by using a spatial smoothing scheme to seamlessly incorporate this filled-in data into the original observation starting from lower latitudes. For recent observations, an extrapolated polar field correction is required. Scaling the average flux density from the prior observations of slightly lower latitudes is found to be a good proxy of the future polar field. This new method has several advantages over some existing methods. It is demonstrated to improve the results of global models such as the Wang-Sheeley-Arge (WSA) model and MHD simulation, especially during the sunspot minimum phase.