We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region （AR） NOAA 11158 obtained from the Helioseismic and Magnetic Image...We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region （AR） NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We also discuss the relation of net current to the observed eruptive events. The AR evolved from the βγ to βγδ3 configuration over a period of six days. The AR had two sub-regions of activity with opposite chirality： one dominated by sunspot rotation producing a strong CME, and the other showing large shear motions producing a strong flare. The net current in each polarity over the CME producing sub-region increased to a maximum and then decreased when the sunspots were separated. The time profile of net current in this sub-region followed the time profile of the rotation rate of the south-polarity sunspot in the same sub-region. The net current in the flaring sub-region showed a sudden increase at the time of the strong flare and remained unchanged until the end of the observation, while the sunspots maintained their close proximity. The systematic evo- lution of the observed net current is seen to follow the time evolution of total length of strongly sheared polarity inversion lines in both of the sub-regions. The observed photospheric net current could be explained as an inevitable product of the emergence of a twisted flux rope, from a higher pressure confinement below the photosphere into the lower pressure environment of the photosphere.展开更多
<img src="Edit_bdc7d851-e537-40df-990c-d678defa9648.png" alt="" />(M = Au, Ag, Cu;<span lang="EN-US" style="font-size:9pt;font-family:"color:black;"><i>n&...<img src="Edit_bdc7d851-e537-40df-990c-d678defa9648.png" alt="" />(M = Au, Ag, Cu;<span lang="EN-US" style="font-size:9pt;font-family:"color:black;"><i>n</i></span>= 1, 2, 3) clusters were used as a cluster model to study the activation of oxygen molecules on single-atom catalysts. Structures of <img src="Edit_bb84deb7-e24a-4777-a2f6-a1621ddd2afc.png" alt="" /> clusters were studied by density functional calculations with global optimization. For each <span style="font-family:"color:black;white-space:normal;"><i>n</i></span>, the most stable structures are quite similar for different metal types, and the oxygen molecule prefers to be adsorbed onto M atoms. It is found that the activation degree of oxygen is higher on clusters with non-noble metal Cu than that of Ag or Au containing clusters, by comparing the changes of O-O bond length and vibrational frequency, natural charge population analysis, Fuzzy bond order analysis, and energy barriers of O<sub>2</sub> dissociation. CO oxidation was used as a probe reaction to study the reactivity of Cu-containing clusters, and it is found that the reactivity decreases with the increase of the size of silicon-oxygen clusters. Our results give a new aspect to understand the reaction mechanism of non-precious metal single-atom catalyst for oxygen activation with high efficiency.展开更多
基金supported by an INSPIRE grant under the AORC scheme of the Department of Science and Technology
文摘We present a detailed investigation of the evolution of observed net vertical current using a time series of vector magnetograms of the active region （AR） NOAA 11158 obtained from the Helioseismic and Magnetic Imager. We also discuss the relation of net current to the observed eruptive events. The AR evolved from the βγ to βγδ3 configuration over a period of six days. The AR had two sub-regions of activity with opposite chirality： one dominated by sunspot rotation producing a strong CME, and the other showing large shear motions producing a strong flare. The net current in each polarity over the CME producing sub-region increased to a maximum and then decreased when the sunspots were separated. The time profile of net current in this sub-region followed the time profile of the rotation rate of the south-polarity sunspot in the same sub-region. The net current in the flaring sub-region showed a sudden increase at the time of the strong flare and remained unchanged until the end of the observation, while the sunspots maintained their close proximity. The systematic evo- lution of the observed net current is seen to follow the time evolution of total length of strongly sheared polarity inversion lines in both of the sub-regions. The observed photospheric net current could be explained as an inevitable product of the emergence of a twisted flux rope, from a higher pressure confinement below the photosphere into the lower pressure environment of the photosphere.
文摘<img src="Edit_bdc7d851-e537-40df-990c-d678defa9648.png" alt="" />(M = Au, Ag, Cu;<span lang="EN-US" style="font-size:9pt;font-family:"color:black;"><i>n</i></span>= 1, 2, 3) clusters were used as a cluster model to study the activation of oxygen molecules on single-atom catalysts. Structures of <img src="Edit_bb84deb7-e24a-4777-a2f6-a1621ddd2afc.png" alt="" /> clusters were studied by density functional calculations with global optimization. For each <span style="font-family:"color:black;white-space:normal;"><i>n</i></span>, the most stable structures are quite similar for different metal types, and the oxygen molecule prefers to be adsorbed onto M atoms. It is found that the activation degree of oxygen is higher on clusters with non-noble metal Cu than that of Ag or Au containing clusters, by comparing the changes of O-O bond length and vibrational frequency, natural charge population analysis, Fuzzy bond order analysis, and energy barriers of O<sub>2</sub> dissociation. CO oxidation was used as a probe reaction to study the reactivity of Cu-containing clusters, and it is found that the reactivity decreases with the increase of the size of silicon-oxygen clusters. Our results give a new aspect to understand the reaction mechanism of non-precious metal single-atom catalyst for oxygen activation with high efficiency.
