A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at lar...A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at large temporal-spatial scale(LTSTMR), the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10^(10)–10^(11); the ratio of observed evolution time to electron gyroperiod is on the order of 10~7–10~9).The original combined acceleration model is known to be one of greatest importance in the interaction of magnetic islands; it assumes that the continuous kinetic-dynamic temporal-spatial scale evolution occurs as two separate independent processes.In this paper, we reconsider the combined acceleration mechanism by introducing a kinetic-dynamic-hydro full-coupled model instead of the original micro-kinetic or macro-dynamic model.We investigate different acceleration mechanisms in the vicinity of neutral points in magnetic islands evolution, from the stage of shrink and breakup into smaller islands(kinetic scale), to the stage of coalescence and growth into larger islands(dynamic scale), to the stages of constant and quasi-constant(contracting-expanding) islands(hydro scale).As a result, we give for the first time the acceleration efficiencies of different types of acceleration mechanisms in magnetic islands' interactions in solar atmosphere LTSTMR activities(pico-, 10^(–2)–10~5 m; nano-, 10~5–10~6 m; micro-, 10~6–10~7 m; macro-, 10~7–10~8 m; large-,10~8–10~9 m).展开更多
Understanding and tuning charge transport over a single molecule is a fundamental topic in molecular electronics.Single-molecule junctions composed of individual molecules attached to two electrodes are the most commo...Understanding and tuning charge transport over a single molecule is a fundamental topic in molecular electronics.Single-molecule junctions composed of individual molecules attached to two electrodes are the most common components built for single-molecule charge transport studies.During the past two decades,rapid technical and theoretical advances in single-molecule junctions have increased our understanding of the conductance properties and functions of molecular devices.In this perspective article,we introduce the basic principles of charge transport in single-molecule junctions,then give an overview of recent progress in modulating single-molecule transport through external stimuli such as electric field and potential,light,mechanical force,heat,and chemical environment.Lastly,we discuss challenges and offer views on future developments in molecular electronics.展开更多
Here we discuss recent progress in understanding tropical cyclone(TC)subseasonal variability and its prediction.There has been a concerted effort to understand the sources of predictability at subseasonal time-scales,...Here we discuss recent progress in understanding tropical cyclone(TC)subseasonal variability and its prediction.There has been a concerted effort to understand the sources of predictability at subseasonal time-scales,and this effort has continued to make progress in recent years.Besides the Madden-Julian Oscillation(MJO),other modes of variability affect TCs at these time-scales,in particular various equatorial waves.Additionally,TC activity is also modulated by extratropical processes via Rossby wave breaking.There has also been progress in the ability of models to simulate the MJO and its modulation of TC activity.Community efforts have created multi-model ensemble datasets,which have made it possible to evaluate the forecast skill of the MJO and TCs on subseasonal time-scales in multiple forecasting systems.While there is positive skill in some cases,there is strong dependence on the ensemble system considered,the basin examined,and whether the storms have extratropical influences or not.Furthermore,the definition of skill differs among studies.Forecasting centers are currently issuing subseasonal TC forecasts using various techniques(statistical,statistical-dynamical and dynamical).There is also a strong interest in the private sector for forecasts with 3-4 weeks lead time.展开更多
基金supported by the strategic priority research program of CAS (XDA17040507, XDA15010900)the national basic research program of China (2013CBA01503)+5 种基金the key program of NSFC (11333007)joint funds of NSFC(U1631130)frontier science key programs of CAS (QYZDJ-SSWSLH012)the program for innovation team of Yunnan Provincethe program for Guangdong introducing Innovative and entrepreneurial teams (2016ZT06D211)the special program for applied research on super computation of the NSFC-Guangdong joint fund (second phase) under No.U1501501
文摘A new combined Fermi, betatron, and turbulent electron acceleration mechanism is proposed in interaction of magnetic islands during turbulent magnetic reconnection evolution in explosive astrophysical phenomena at large temporal-spatial scale(LTSTMR), the ratio of observed current sheets thickness to electron characteristic length, electron Larmor radius for low-β and electron inertial length for high-β, is on the order of 10^(10)–10^(11); the ratio of observed evolution time to electron gyroperiod is on the order of 10~7–10~9).The original combined acceleration model is known to be one of greatest importance in the interaction of magnetic islands; it assumes that the continuous kinetic-dynamic temporal-spatial scale evolution occurs as two separate independent processes.In this paper, we reconsider the combined acceleration mechanism by introducing a kinetic-dynamic-hydro full-coupled model instead of the original micro-kinetic or macro-dynamic model.We investigate different acceleration mechanisms in the vicinity of neutral points in magnetic islands evolution, from the stage of shrink and breakup into smaller islands(kinetic scale), to the stage of coalescence and growth into larger islands(dynamic scale), to the stages of constant and quasi-constant(contracting-expanding) islands(hydro scale).As a result, we give for the first time the acceleration efficiencies of different types of acceleration mechanisms in magnetic islands' interactions in solar atmosphere LTSTMR activities(pico-, 10^(–2)–10~5 m; nano-, 10~5–10~6 m; micro-, 10~6–10~7 m; macro-, 10~7–10~8 m; large-,10~8–10~9 m).
基金This work was supported by the National Natural Science Foundation of China(21788102,21790361,22175064,22073109,and 92161122)Shanghai Municipal Sci.&Tech.Major Project(2018SHZDZX03)+1 种基金the 111 Project(B16017)the Fundamental Research Funds for the Central Universities.
文摘Understanding and tuning charge transport over a single molecule is a fundamental topic in molecular electronics.Single-molecule junctions composed of individual molecules attached to two electrodes are the most common components built for single-molecule charge transport studies.During the past two decades,rapid technical and theoretical advances in single-molecule junctions have increased our understanding of the conductance properties and functions of molecular devices.In this perspective article,we introduce the basic principles of charge transport in single-molecule junctions,then give an overview of recent progress in modulating single-molecule transport through external stimuli such as electric field and potential,light,mechanical force,heat,and chemical environment.Lastly,we discuss challenges and offer views on future developments in molecular electronics.
文摘Here we discuss recent progress in understanding tropical cyclone(TC)subseasonal variability and its prediction.There has been a concerted effort to understand the sources of predictability at subseasonal time-scales,and this effort has continued to make progress in recent years.Besides the Madden-Julian Oscillation(MJO),other modes of variability affect TCs at these time-scales,in particular various equatorial waves.Additionally,TC activity is also modulated by extratropical processes via Rossby wave breaking.There has also been progress in the ability of models to simulate the MJO and its modulation of TC activity.Community efforts have created multi-model ensemble datasets,which have made it possible to evaluate the forecast skill of the MJO and TCs on subseasonal time-scales in multiple forecasting systems.While there is positive skill in some cases,there is strong dependence on the ensemble system considered,the basin examined,and whether the storms have extratropical influences or not.Furthermore,the definition of skill differs among studies.Forecasting centers are currently issuing subseasonal TC forecasts using various techniques(statistical,statistical-dynamical and dynamical).There is also a strong interest in the private sector for forecasts with 3-4 weeks lead time.
