The present study proposes a new mechanism to cause a strong electron heating in the magnetic islands ejected from the reconnection current layer. A large‐scale full kinetic simulation in ...three‐dimensional system demonstrates that the electrons are effectively accelerated by the non‐ideal electric field generated through the electromagnetic turbulence excited in the magnetic islands. It is found that the high‐energy electrons are efficiently scattered by the turbulence, resulting in the strong electron heating. The existence of turbulence and the associated non‐ideal electric field in the magnetic islands is consistent with recent satellite observations in the Earth’s magnetosphere.
Plain Language Summary
Observed velocity distribution of space plasmas often contains high‐energy components overlapping the ambient thermal component, implying the existence of local explosive processes producing energetic particles. Magnetic reconnection is one of such the processes, converting the magnetic field energy into plasma kinetic energies. In this study, we propose a new mechanism to cause a strong electron heating in the magnetic islands generated during magnetic reconnection. By means of a large‐scale computer simulation, where both electrons and ions are treated as particles, we found that the electrons are effectively accelerated by turbulence‐induced electric field. The high‐energy electrons are efficiently scattered by the turbulence, resulting in the strong electron heating. The existence of turbulence and the associated induction electric field is consistent with recent satellite observations in the Earth’s magnetosphere.
Key Points
We propose a new mechanism to accelerate electrons in the magnetic islands via turbulence‐induced electric field
The accelerated electrons are efficiently scattered by the electromagnetic turbulence, resulting in strong electron heating
The existence of non‐ideal electric field and turbulence in the magnetic islands is consistent with satellite observations
This paper investigates the projective synchronization of fractional-order memristor-based neural networks. Sufficient conditions are derived in the sense of Caputo’s fractional derivation and by ...combining a fractional-order differential inequality. Two numerical examples are given to show the effectiveness of the main results. The results in this paper extend and improve some previous works on the synchronization of fractional-order neural networks.
High-safety and low-cost aqueous zinc-ion batteries (ZIBs) are an exceptionally compelling technology for grid-scale energy storage, whereas the corrosion, hydrogen evolution reaction and dendrite ...growth of Zn anodes hamper their further development, which are derived from the decomposition of active water molecules belonging to Zn2+ solvation structures in electrolytes. In recent years, strategies of regulating Zn2+ solvation shells in electrolytes have been demonstrated to effectively suppress the above-mentioned issues, and fruitful achievements have been made. However, there is a lack of systematic summary on the functional mechanisms and solvation structure evolution of electrolytes or electrolyte additives. Herein, this review gives a comprehensive introduction of the solvation structure regulation strategies based on electrolyte engineering for dendrite-free and side reaction-suppressed ZIBs, including high-concentration electrolytes, deep eutectic solvents, ionic liquids, functional additives, solid-state electrolytes and super-saturated electrolyte layers, particularly an in-depth and fundamental understanding of the effects and mechanisms of electrolyte modification on Zn2+ solvation shells. Furthermore, the general performance metrics of the above-mentioned strategies, potential directions and perspectives for further research are proposed.
Recent magnetospheric observations and three‐dimensional (3D) kinetic simulations have shown that plasma wave activities are significantly enhanced around the reconnection x‐line, implying that the ...reconnection process is fully 3D. However, how the turbulence affects the local reconnection process has been poorly understood so far. We find by means of large‐scale particle‐in‐cell simulation in 3D system that the local reconnection rate can be significantly enhanced, reaching 0.4, which is much larger than theoretical predictions for two‐dimensional (2D) reconnection. The large reconnection rate is associated with large energy conversion rate and strong electron acceleration. The enhancement of the reconnection rate is caused by local increases of electron momentum transport and pressure gradient force induced by turbulence, which can not occur in 2D system. The result is expected to give better interpretations to in‐situ satellite observations where magnetic reconnection proceeds in 3D system.
Plain Language Summary
Magnetic reconnection is an important process in space physics to convert the magnetic field energy into particle kinetic energy. In this study, we investigate reconnection rate, a physical quantity that measures the speed of magnetic reconnection by using fully kinetic simulation, in which both electrons and ions are particles. We find very fast local reconnection processes in three‐dimensional system that far exceeds expectation. It indicates that magnetic reconnection is a three‐dimensional process. The high reconnection rate comes from the electrons rather than ions. And the main reason is the increasing of electron momentum transport and pressure gradient caused by strong turbulence, leading to a strong magnetic reconnection process in the current sheet.
Key Points
Magnetic reconnection can be strongly intensified in turbulent current sheet with the local reconnection rate exceeding 0.4
High reconnection rate is caused by local enhancements of electron momentum transport and pressure gradient force induced by turbulence
Reconnection process is essentially 3D, suggesting that local satellite observations may be insufficient in capturing the global process
Satellite observations indicate that multiple components often exist in the plasma sheet, particularly during impulsive fast flow events. In this paper, we perform a kinetic analysis of the energy ...transport of plasma sheet ion flow using a model of two‐component plasma sheet ion flows (Background convection flow represented by subscript “b” and Fast flow represented by subscript “f”) and compare the energy transport calculated by kinetic approach Qk with those obtained from magnetohydrodynamic (MHD) approach QMHD. The ratio of Qk/QMHD is always larger than unity and is positively proportional to the ratios of Vf/Vb and Tf/Tb. The maximum values of Qk/QMHD occur in the low‐speed ranges (i.e., small density ratio Nf/N). When Nf/N exceeds 0.4, the ratio of Qk/QMHD is almost the same for a wide parameter ranges of Vf, Tf, and Vb. Heat flux is important in low‐speed range and is neglectable in the high‐speed range. The adiabatic polytropic index 5/3 cannot correctly describe energy transport rate. A density ratio Nf/N of 0.3% of high‐speed ion flow can make the effective polytropic index obviously deviate from adiabatic polytropic index (5/3). The above theoretic results can well explain previously reported satellite in situ observations.
Key Points
We study the kinetic theory of energy transport of two ion components in order to explain recent observations of plasma sheet
The ratio of energy transport rates calculated by kinetic and MHD approaches is larger than 1, and its maximum value is in low‐speed range
For calculating MHD energy transport rate, adiabatic assumption is invalid and the effective polytropic index obviously deviate from 5/3
To solve the poor cycling stability of zinc ion batteries (ZIBs) caused by the growth of zinc (Zn) dendrites, a novel method of separator modification is proposed. Herein, graphene oxide (GO), which ...has many outstanding properties, is applied as a modified material to a glass fiber (GF) separator using a simple vacuum filtration method. A stable and dendrite-free Zn anode can be obtained after 500 cycles in a Zn//Zn symmetrical battery when using a modified separator (GF/GO1), which is mainly owing to the preferential growth of the non-protruding crystal planes of the zinc metal and the uniform nucleation of zinc ions under the action of GO. As proof of concept, full Zn//MnO
2
batteries with a GF/GO1 separator exhibited a high specific capacity of 126 mA h g
−1
at 0.1 A g
−1
, a high energy density of 327.5 W h kg
−1
(power density of 0.517 W kg
−1
), and a high power density of 20.8 kW kg
−1
(energy density of 253.8 W h kg
−1
), demonstrating significant improvements compared with the unmodified GF separator. Meanwhile, ZIBs with a GF/GO1 separator exhibited excellent long-term stability with less than 25% capacity fade over 500 cycles at a current density of 0.5 A g
−1
. ZIBs with a GF separator retain only 37% of their initial capacity after 100 cycles. Furthermore, the GF/GO1 separator can also help to improve the cycle performance and rate performance of lithium metal batteries and to achieve a dendrite-free lithium anode. Full batteries of Li//GF/GO1//LiCoO
2
show improved rate and cycling capabilities. A higher energy density of 537.1 W h kg
−1
at 0.04 kW kg
−1
and higher power density of 1.4 kW kg
−1
at 264.6 W h kg
−1
can be achieved with a GF/GO1 separator, which is better than many Li metal batteries. This modification of the separator provides an effective approach to designing next-generation batteries exhibiting excellent rate and cycling capabilities, and high energy and power densities.
A universal and facile approach using a graphene oxide (GO) modified separator is used to suppress dendrite formation in Zn and Li metal anodes,
via
the preferential growth of non-protruding crystal planes.
Predictability of the Solar Cycle Over One Cycle Jiang, Jie; Wang, Jing-Xiu; Jiao, Qi-Rong ...
Astrophysical journal/The Astrophysical journal,
08/2018, Letnik:
863, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The prediction of the strength of future solar cycles is of interest because of its practical significance for space weather and as a test of our theoretical understanding of the solar cycle. The ...Babcock-Leighton mechanism allows predictions by assimilating the observed magnetic field on the surface. Since the emergence of sunspot groups has random properties, making it impossible to accurately predict the solar cycle and strongly limiting the scope of cycle predictions, we develop a scheme to investigate the predictability of the solar cycle over one cycle. When a cycle has been ongoing for more than three years, the sunspot group emergence can be predicted along with its uncertainty during the rest time of the cycle. The method for this prediction is to start by generating a set of random realizations that obey the statistical relations of the sunspot emergence. We then use a surface flux transport model to calculate the possible axial dipole moment evolutions. The correlation between the axial dipole moment at cycle minimum and the subsequent cycle strength and other empirical properties of solar cycles are used to predict the possible profiles of the subsequent cycle. We apply this scheme to predict the large-scale field evolution from 2018 to the end of cycle 25, whose maximum strength is expected to lie in the range from 93 to 155 with a probability of 95%.
Biomass has attracted considerable attention from both researchers and practitioners as an important renewable energy source that can help achieve sustainable development. However, inefficient ...biomass logistics systems hinder the development of biomass utilisation. This study investigates a two-echelon biomass resource location-routing problem (2E-BRLRP). Considering a predetermined supply of biomass resources, a mixed integer programming model for the 2E- BRLRP is established to determine the best locations for biomass collection facilities and corresponding vehicle routes. To address the computational complexity, a hybrid heuristic algorithm that embeds variable neighbourhood search into the tabu search framework is developed. A set of comprehensive computational examples are used to test the effectiveness and efficiency of the proposed approach.
•This study investigates a two-echelon biomass resource location-routing problem.•A novel mixed integer programming model is established for the proposed problem.•A hybrid heuristic algorithm is developed for problem solution.•Comprehensive computational examples are conducted to verify the proposed approach.
High demands for broadband mobile wireless communications and the emergence of new wireless multimedia applications constitute the motivation to the development of broadband wireless access ...technologies in recent years. The Long Term Evolution/System Architecture Evolution (LTE/SAE) system has been specified by the Third Generation Partnership Project (3GPP) on the way towards fourth-generation (4G) mobile to ensure 3GPP keeping the dominance of the cellular communication technologies. Through the design and optimization of new radio access techniques and a further evolution of the LTE systems, the 3GPP is developing the future LTE-Advanced (LTE-A) wireless networks as the 4G standard of the 3GPP. Since the 3GPP LTE and LTE-A architecture are designed to support flat Internet Protocol (IP) connectivity and full interworking with heterogeneous wireless access networks, the new unique features bring some new challenges in the design of the security mechanisms. This paper makes a number of contributions to the security aspects of the LTE and LTE-A networks. First, we present an overview of the security functionality of the LTE and LTE-A networks. Second, the security vulnerabilities existing in the architecture and the design of the LTE and LTE-A networks are explored. Third, the existing solutions to these problems are classically reviewed. Finally, we show the potential research issues for the future research works.
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