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Electron cyclotron harmonic (ECH) waves are one of the most common plasma waves in the Earth's magnetosphere, and they are considered to be excited by the electron loss‐cone distributions near the magnetic equator. Using the Magnetospheric Multiscale data, we report an unusual event of ECH waves at L = ∼12.4 and MLT = ∼16.0 hr, where the ECH waves are locally excited inside non‐propagating magnetic oscillations, that is, mirror mode structures. The observation reveals that the mirror mode structures are generated by anisotropic ions (Ti⊥/Ti∥ ${T}_{i\perp }/{T}_{i{\Vert} }$ ∼ 1.3 – 1.7), and electron mirror loss‐cone distributions are formed due to the magnetic configuration of the mirror mode structures. Combing with the linear instability analysis, we confirm that the ECH waves are locally excited by the electron mirror loss‐cone distributions inside the mirror mode structures. Therefore, we propose that the mirror mode structures provide another potential source region for ECH waves in the Earth's magnetosphere. Plain Language Summary: Electron cyclotron harmonic (ECH) waves are widely observed in the Earth's magnetosphere, which are important for the diffusion auroral precipitation. Previous studies have shown that the main source region of ECH waves in the magnetosphere is near the magnetic equator, and the electron loss‐cone distribution provides the free energy to excite ECH waves. In this study, we reveal that there also exists another potential source region of ECH waves, that is, mirror mode structures. Using the Magnetospheric Multiscale data, we report an unusual event of ECH waves inside the mirror mode structures in the Earth's outer magnetosphere. By analyzing the plasma conditions, we show that the mirror mode structures are generated by anisotropic ions, and electron mirror loss‐cone distributions are formed due to the magnetic configuration of the mirror mode structures. Based on the linear instability analysis, we demonstrate that the ECH waves are excited by the electron mirror loss‐cone distributions within the mirror mode structures. These results provide new insights into the generation of ECH waves in the Earth's magnetosphere. Key Points: Using the Magnetospheric Multiscale data, we report the first observation of electron cyclotron harmonic (ECH) waves within mirror mode structures in the Earth's outer magnetosphereThe mirror mode structures observed as quasi‐periodic magnetic oscillations are excited by anisotropic ionsThe simultaneously detected ECH waves are excited by the electron mirror loss‐cone distributions inside the mirror mode structures [ABSTRACT FROM AUTHOR]

Magnetic reconnection is a fundamental plasma process by which magnetic field lines on two sides of the current sheet flow inward to yield an X-line topology. It is responsible for producing energetic electrons in explosive phenomena in space, astrophysical, and laboratorial plasmas. The X-line region is supposed to be the important place for generating energetic electrons. However, how these energetic electrons are generated in such a limited region is still poorly understood. Here, using Magnetospheric multiscale mission data acquired in Earth's magnetotail, we present direct evidence of super-thermal electrons up to 300 keV inside an X-line region, and the electrons display a power-law spectrum with an index of about 8.0. Concurrently, three-dimensional network of dynamic filamentary currents in electron scale is observed and leads to electromagnetic turbulence therein. The observations indicate that the electrons are effectively accelerated while the X-line region evolves into turbulence with a complex filamentary current network. Magnetotail reconnection plays an important role in explosive energy conversion. Here, the authors show direct evidence of super-thermal electrons up to 300 keV within X-line region in Earth's magnetotail, indicating effective electron acceleration due to turbulence. [ABSTRACT FROM AUTHOR]

In this paper, by performing two‐dimensional (2‐D) particle‐in‐cell simulations of collisionless magnetic reconnection in a Harris current sheet, we analyze the formation of electron inflow along the separatrices toward the X‐line from the perspective of fluid. The results show that both the parallel electric field and mirror force can drive the electron inflow to stream toward the X‐line. The speed of the electron inflow can reach about 4VA(where VA is the Alfvén speed based on the upstream asymptotic magnetic field magnitude and peak density in the current sheet). Although the contribution of the parallel electric field is much larger than that of the mirror force, the mirror force cannot be ignored. When the electron inflow streams toward the X‐line, it is heated in the parallel direction. The resulted gradient of the parallel electron pressure leads to the attenuation of the electron inflow. We also investigate the effects of the density and temperature of the background plasma on the formation of the electron inflow. With the decrease of the background plasma density, the contribution of the parallel electric field becomes larger while that of the mirror force almost remains unchanged. With the decrease of the background plasma temperature, the contribution of the parallel electric field becomes larger while that of the mirror force becomes smaller. Plain Language Summary: Magnetic reconnection is a universal process in which the topology of the magnetic field changes, accompanied by plasma heating and particle acceleration. During reconnection, electrons moving along the separatrices toward the X‐line form the electron inflow. The electron inflow has been confirmed in simulations and observations, but its generation mechanism remains unclear. This paper focuses on the dynamics of inflow electrons along the separatrices during magnetic reconnection, and quantitatively analyzes the formation of electron inflow. We found that the formation of electron inflow is contributed by three effects: accelerated by the parallel electric field, accelerated by the magnetic mirror force, and decelerated by the gradient of parallel electron pressure. The acceleration contribution of the parallel electric field is dominant, but that of mirror force cannot be ignored, especially when the background plasma density and temperature are sufficiently high. Key Points: Electron inflow is accelerated by parallel electric field and mirror force and decelerated by the gradient of parallel electron pressureParallel electric field plays a major role in the formation of electron inflow, while the contribution of mirror force cannot be ignoredThe contributions of parallel electric field and mirror force change with the background plasma density and temperature [ABSTRACT FROM AUTHOR]

The power gap around 0.5Ωe (where Ωe is the equatorial electron gyrofrequency) of whistler‐mode waves is commonly observed in the Earth's inner magnetosphere, but its generation mechanism is still under debate. By performing two‐dimensional particle‐in‐cell simulations in a uniform background magnetic field, we investigate the spectral properties of whistler‐mode waves excited by temperature anisotropic electrons. The waves have positive growth rates in a wide range of normal angles (θ ≈ 0°–35°), resulting in the generation of both parallel and nonparallel waves. Although the nonparallel wave modes are weaker than the parallel ones, they can cause the plateau‐like shape around 0.5 VAe (where VAe represent the electron Alfven speed) in the parallel direction of electron velocity distribution. The plateau‐like electron component can then lead to severe damping in the waves around 0.5Ωe via the cyclotron resonance, and the power gap is formed. This mechanism is called as "spectrum bite". Our study sheds fresh light on the well‐known gap formation at ∼0.5Ωe in the whistler‐mode waves, which is ubiquitously detected near the equator in the inner magnetosphere. Key Points: The whistler‐mode waves with power gaps around 0.5Ωe in the Earth's magnetosphere are investigated by 2‐D PIC simulationsThe power gap is formed due to the severe damping by the plateau‐like electron component in the parallel velocity distribution at ∼0.5VAeThe plateau‐like distribution in the parallel direction is caused by the nonparallel wave modes through Landau resonance [ABSTRACT FROM AUTHOR]

Whistler‐mode waves can modulate the electron distributions through wave‐particle interactions in the Earth's inner magnetosphere. In this paper, we have investigated the effects of the whistler waves on the electron distributions by a combination of electron magnetohydrodynamics and test‐particle simulations. Our simulations show a parallel whistler wave becomes gradually oblique during its propagation from the magnetic equator to higher latitudes. Such a whistler wave causes distinct flux increases of tens of keV electrons at large pitch angles to form electron butterfly distributions. This whistler wave traps numerous resonant electrons and transports them from lower latitudes to higher latitudes through nonlinear Landau trapping. Meanwhile, these trapped electrons are efficiently accelerated to higher energies contributing to the rapid formation of electron butterfly distributions at higher latitudes. Our study suggests nonlinear Landau trapping is a potential formation mechanism of the electron butterfly distributions observed in the Earth's inner magnetosphere. Plain Language Summary: Wave‐particle interactions are known to play an important role in regulating energetic electron distributions in the Earth's inner magnetosphere. In particular, whistler‐mode waves can efficiently modulate the electron distributions by cyclotron and Landau resonant interactions. In this paper, we used a 2‐D electron magnetohydrodynamics model to simulate a whistler wave in the dipole geomagnetic field. The simulation results indicate a parallel whistler wave becomes gradually oblique during its propagation from the magnetic equator to high latitudes. Furthermore, a test‐particle simulation shows that such a whistler wave can trap and accelerate electrons from the lower latitudes to higher latitudes by nonlinear Landau trapping, which leads to the rapid formation of electron butterfly distributions at tens of keV. Previous studies suggested that nonlinear cyclotron trapping can cause electron butterfly distributions at tens of keV observed in the Earth's magnetosphere. Our study provides a new potential formation mechanism of electron butterfly distributions in the Earth's magnetosphere. Key Points: Effects of whistler waves on electron distributions have been studied by a combination of electron magnetohydrodynamics and test‐particle simulationsA whistler wave causes distinct flux enhancements of 10s keV electrons at large pitch angles to form electron butterfly distributionsNonlinear Landau trapping contributes to the rapid formation of the electron butterfly distributions [ABSTRACT FROM AUTHOR]

We report nonlinear wave–wave coupling related to whistler-mode or electron Bernstein waves in the near-Sun slow solar wind with Parker Solar Probe (PSP) data. Prominent plasma wave power enhancements usually exist near the electron gyrofrequency (fce), identified as electrostatic whistler-mode and electron Bernstein waves (Malaspina et al. 2020). We find that these plasma waves near fce typically have a harmonic spectral structure and further classify them into three types identified by the characteristics of wave frequency and electric power. For short, we will call these type i , type ii , and type iii waves. The first (type i) is the quasi-electrostatic whistler-mode wave and its second harmonic, which resembles the quasi-electrostatic multiband chorus in the Earth's magnetosphere. The second (type II) is the pure electron Bernstein wave. The last (type iii) is an intermixture of whistler-mode and electron Bernstein waves, where the wave mode driven by the coupling between them was also detected. During the first five orbits of PSP, the type iii spectra have the largest occurrence rate, then the type i spectra. The type ii spectra are the rarest type of wave. Our study reveals that nonlinear wave–wave coupling in the solar wind may be as common as in the Earth's magnetosphere. [ABSTRACT FROM AUTHOR]

Atmospheric escape is a fundamental process in the long‐term habitability evolution of terrestrial planets. Recent observations on Mars have found the concurrence of the severe ionospheric erosion and the large‐amplitude, quasi‐perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. Here we propose a new candidate mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. In contrast to the cyclotron resonance with oxygen atomic and molecular ions above the escape energies, the magnetosonic waves Landau‐resonate with the thermal electrons at energy channels of the order of 0.01–0.1 eV. Through the Landau resonance over tens of minutes, the large‐amplitude (12 nT) magnetosonic waves can heat the topside ionospheric electrons to ∼2 times the normal temperature. The topside ionospheric electron heating could result in the enhancement of the ambipolar electric potential and eventually facilitate the escape of ionospheric plasma. Plain Language Summary: An atmosphere of sufficient density is a fundamental condition for a habitable terrestrial planet. Mars as a terrestrial planet in the habitable zone of our solar system lost much of its atmosphere over billions of years and has thus become a unique testing ground to understand the planetary atmospheric loss processes. Recent observations on Mars have shown that the severe erosion of the ionosphere, an ionized part of the upper atmosphere, was accompanied by the large‐amplitude, quasi‐perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. On the basis of space observations and numerical calculations, we propose a new physical mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. The large‐amplitude magnetosonic waves can heat the topside ionospheric electrons to ∼2 times the normal temperature over tens of minutes, enhance the ambipolar electric potential, and eventually facilitate the escape of ionospheric plasma. The electron Landau heating process may also contribute to the ionospheric erosion of other terrestrial planets within and beyond our solar system. Key Points: Magnetosonic waves are difficult to cyclotron‐resonate with Martian ionospheric oxygen atomic and molecular ions below the escape energiesStrong magnetosonic waves can Landau‐heat Martian topside ionospheric electrons to 2 times the normal temperature over tens of minutesElectron Landau heating by magnetosonic waves may facilitate the Martian ionospheric erosion by enhancing the ambipolar electric field [ABSTRACT FROM AUTHOR]

Suprathermal electrons are a major heat source of ionospheric plasma. How the suprathermal electrons evolve during their bounces inside the plasmasphere is a fundamental question for the magnetosphere‐ionosphere coupling. On the basis of Van Allen Probes observations and quasi‐linear simulations, we present here the first quantitative study on the evolution of suprathermal electrons under the competition between Landau heating by whistler mode hiss waves and Coulomb collisional cooling by background plasma inside a plasmaspheric plume. We show that the Landau heating can prevail over the collisional cooling for >50 eV electrons and cause the field‐aligned suprathermal electron fluxes to increase by up to 1 order of magnitude within 1.5 hr. Our results imply that the plasmaspheric plume hiss waves could mediate energy from the ring current electrons to the ionospheric plasma. Plain Language Summary: The ionospheric plasma temperature variation can affect the Earth's atmospheric escape and the spacecraft orbit decay. A major heat source of the ionospheric plasma is the suprathermal (several eV to hundreds of eV) electrons, which can bounce along the magnetic field lines inside the plasmasphere. How these suprathermal electrons evolve during their bounces is a fundamental question for the magnetosphere‐ionosphere coupling. In the past, the plasmaspheric suprathermal electrons were usually considered to gain energy from the ring current ions through Coulomb collisions and wave‐particle interactions. Here we show that strong whistler mode hiss waves can grow from the instability of the ring current electrons in the plasmaspheric drainage plume, and their Landau heating can prevail over the collisional cooling by background plasma for >50 eV electrons. The enhanced field‐aligned suprathermal electrons could eventually heat the ionospheric plasma. These results have significant implications for understanding the energy transfer process from the magnetosphere to the ionosphere. Key Points: The collisional cooling by background plasma counteracts largely the Landau heating by hiss waves for <50 eV electronsThe Landau heating can increase the field‐aligned fluxes of >50 eV electrons by 1 order of magnitude within 1.5 hrPlasmaspheric plume hiss could mediate energy from the ring current electrons through the suprathermal electrons to the ionospheric plasma [ABSTRACT FROM AUTHOR]

Whistler mode chorus waves in the Earth's inner magnetosphere are usually composed of discrete elements, and each element can be characterized by the following properties: the amplitude, the duration, the frequency span, and the frequency chirping rate. Using a one‐dimensional (1‐D) particle‐in‐cell (PIC) simulation code, we study the dependence of these properties of a rising‐tone chorus on the number density nheq/nc0 and temperature anisotropy AT of energetic electrons at the magnetic equator. The whistler waves are first excited around the magnetic equator by anisotropic energetic electrons and then develop into a rising‐tone chorus when they leave away from the equator. During the propagation toward the pole, the rising‐tone chorus with nearly constant frequency span first enhances and then decays. Its frequency chirping rate declines in the early stage and then gradually increases. Meanwhile, the chorus duration is quite the opposite due to propagation effect. Over a suitable range of nheq/nc0 to generate rising‐tone chorus, the frequency chirping rate of the excited rising‐tone chorus first increases and then saturates, while its saturated amplitude, duration, and frequency span have a rising tendency with the increasing nheq/nc0. As for AT, the frequency chirping rate of the generated rising‐tone chorus is increasing with the increase of AT that is consistent with prediction of nonlinear theory, while the duration is just the opposite. Our simulation study can give a further understanding of the generation and propagation of rising‐tone chorus waves. Key Points: The frequency chirping rate and the duration of the rising‐tone chorus excited near the magnetic equator change due to propagation effectThe amplitude, duration and frequency span of the rising‐tone chorus increase with the increasing number density of energetic electronsThe frequency chirping rate increases with increasing temperature anisotropy of energetic electrons, while the duration is the opposite [ABSTRACT FROM AUTHOR]

Near equatorial (fast) magnetosonic waves, characterized by high magnetic compressibility, are whistler‐mode emissions destabilized by proton shell/ring distributions. In the past, substorm proton injections are widely known to intensify magnetosonic waves in the inner magnetosphere. Here we report the unexpected observations by the Van Allen Probes of the magnetosonic wave quenching associated with the substorm proton injections under both high‐ and low‐density conditions. The enhanced proton thermal pressure distorted the background magnetic field configuration and the cold plasma density distribution. The reduced phase velocities locally allowed the weak growth or even damping of magnetosonic waves. Meanwhile, the spatially irregularly varying refractive indices might suppress the cumulative growth of magnetosonic waves. For intense injections, this wave quenching region could extend over 2 hr in magnetic local time and 0.5 Earth radii in radial distance. These results provide a new understanding of the generation and distribution of magnetosonic waves. Plain Language Summary: Magnetosonic waves are the near‐equatorially confined electromagnetic emissions between the proton gyrofrequency and the lower hybrid frequency in the magnetosphere. Theoretical and observational studies have demonstrated the potential of the magnetosonic waves to accelerate the radiation belt electrons. It is therefore important to understand the generation process and the spatiotemporal distribution of the magnetosonic waves. The substorm activities injecting hot protons into the inner magnetosphere are conventionally considered to intensify the magnetosonic waves. By analyzing the wave and particle data of the Van Allen Probes, we find a magnetosonic wave quenching region related to the distortion of the background magnetic field configuration and the cold plasma density distribution closely following the substorm injection front. We propose two possible causes for this phenomenon: (1) local weak growth or even damping of the magnetosonic waves with the reduced phase velocities and (2) suppression of the magnetosonic wave cumulative growth in the disturbed medium. This new finding may help refine the modeling of the magnetosonic waves and then the radiation belt electrons. Key Points: The enhanced thermal pressure of hot protons can distort the geomagnetic field configuration and the cold plasma density distributionThe magnetosonic wave quenching region can emerge closely following the substorm injection front under both high‐ and low‐density conditionsThe magnetosonic wave quenching region can extend over 2 hr in magnetic local time and 0.5 Earth radii in radial distance [ABSTRACT FROM AUTHOR]

Rising‐tone chorus waves have already been successfully produced in a mirror magnetic field with the use of one‐ and two‐dimensional particle‐in‐cell (PIC) simulations. However, in reality, the background magnetic field in the inner Earth's magnetosphere is a dipole magnetic field, unlike symmetric mirror fields. In this paper, with the two‐dimensional (2‐D) general curvilinear PIC (gcPIC) code, we investigate the generation of rising‐tone chorus waves in the dipole magnetic field configuration. The plasma consists of three components: immobile ions, cold background, and hot electrons. In order to save computational resource, the topology of the magnetic field is roughly equal to that at L = 0.6 RE, although the plasma parameters corresponding to those at L = 6 RE (RE is the Earth's radius) are used. Whistler mode waves are first excited around the magnetic equator by the hot electrons with a temperature anisotropy. The excited whistler mode waves propagate almost parallel and antiparallel to the background magnetic field in their source region, which is limited at ∣λ ∣  ≤ 3° (where λ is the magnetic latitude). When the waves leave from the source region and propagate toward high latitudes, both their amplitude and wave normal angle become larger. However, the group velocity of the waves is directed toward high latitudes almost along the magnetic field. During such a process, the waves have a frequency chirping, as shown by a rising tone in the frequency‐time spectrogram. To our best knowledge, it is for the first time that rising‐tone chorus are generated in a dipole magnetic field with a PIC simulation. Key Points: The rising‐tone chorus waves are generated in a dipole magnetic field with a 2‐D gcPIC simulation for the first timeWhistler waves are excited around the magnetic equator and propagate almost along the background magnetic fieldWhen whistler waves propagate toward high latitudes, their wave normal angles increase with the growth of the latitude [ABSTRACT FROM AUTHOR]

Abstract: The excitation of magnetosonic waves in the meridian plane of a rescaled dipole magnetic field is investigated, for the first time, using a general curvilinear particle‐in‐cell simulation. Our simulation demonstrates that the magnetosonic waves are excited near the equatorial plane by tenuous ring distribution protons. The waves propagate nearly perpendicularly to the background magnetic field along both radially inward and outward directions. Different speeds of inward and outward propagation result in the asymmetrical distribution about the source region. The waves are accompanied by energization of both cool protons and electrons near the wave source region. The cool protons are heated perpendicularly, while the cool electrons can be heated in the parallel direction and also experience enhanced perpendicular drift at the presence of intense wave power. The implications of simulation results to the observations of magnetosonic waves and related particle heating in the inner magnetosphere are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, by taking advantage of a two-dimensional particle-in-cell simulation model, we study the structure of the out-of-plane magnetic field (Hall magnetic field) during asymmetric magnetic reconnection without a guide field, and the associated in-plane current system is also analyzed. The evolution of asymmetric reconnection has two stages. At the first stage, the electrons move toward the X line along the separatrix in the magnetosheath side, and depart from the X line along the separatrix in the magnetosphere side. Another electron flow toward the X line exists above the separatrix in the magnetosphere side. The resulted in-plane current system, which is mainly determined by electron dynamics, generates the quadrupolar structure of the Hall magnetic field, where the two quadrants in the magnetosheath side are much stronger than those in the magnetosphere side. At the second stage, besides these electron flows, an additional electron flow away from the X line is formed along the magnetic field below the separatrix in the magnetosheath side. A hexapolar structure of the Hall magnetic field is then generated by such a current system. [ABSTRACT FROM AUTHOR]

Whistler-mode waves play a crucial role in controlling electron dynamics in the Earth’s Van Allen radiation belt, which is increasingly important for spacecraft safety. Using THEMIS waveform data, Gao et al. [X. L. Gao, Q. Lu, J. Bortnik, W. Li, L. Chen, and S. Wang, Geophys. Res. Lett., 43, 2343-2350, 2016] have reported two multiband chorus events, wherein upper-band chorus appears at harmonics of lower-band chorus. They proposed that upper-band harmonic waves are excited through the nonlinear coupling between the electromagnetic and electrostatic components of lower-band chorus, a second-order effect called “lower band cascade”. However, the theoretical explanation of lower band cascade was not thoroughly explained in the earlier work. In this paper, based on a cold plasma assumption, we have obtained the explicit nonlinear driven force of lower band cascade through a full nonlinear theoretical analysis, which includes both the ponderomotive force and coupling between electrostatic and electromagnetic components of the pump whistler wave. Moreover, we discover the existence of an efficient energy-transfer (E-t) channel from lower-band to upper-band whistler-mode waves during lower band cascade for the first time, which is also confirmed by PIC simulations. For lower-band whistler-mode waves with a small wave normal angle (WNA), the E-t channel is detected when the driven upper-band wave nearly satisfies the linear dispersion relation of whistler mode. While, for lower-band waves with a large WNA, the E-t channel is found when the lower-band wave is close to its resonant frequency, and the driven upper-band wave becomes quasi-electrostatic. Through this efficient channel, the harmonic upper band of whistler waves is generated through energy cascade from the lower band, and the two-band spectral structure of whistler waves is then formed. Both two types of banded whistler-mode spectrum have also been successfully reproduced by PIC simulations. [ABSTRACT FROM AUTHOR]

An electron phase-space hole (electron hole) is considered to be unstable to the transverse instability. In this paper, two-dimensional (2D) electrostatic particle-in-cell (PIC) simulations are used to explore the dissipation process of a one-dimensional (1D) electron hole in a weakly magnetized plasma and its consequence on electron heating, which consists of two stages. In the first stage, the electron hole is still kept as a quasi-1D structure, however, with the excitation of the transverse instability and the generation of the perpendicular electric field, the electrons are scattered and then heated along the perpendicular direction in the electron hole. In the second stage, the quasi-1D electron hole is broken into several 2D electron holes. The temperature of the electrons outside of these 2D electron holes also increase, and at last the velocity distribution of the electrons become almost isotropic in the whole simulation domain. Our results provide a new dissipation mechanism of an electron hole. [ABSTRACT FROM AUTHOR]

It is well known that the parallel cuts of the parallel and perpendicular electric field in electron phase-space holes (electron holes) have bipolar and unipolar structures, respectively. Recently, electron holes in the Earth's plasma sheet have been observed by THEMIS satellites to have detectable fluctuating magnetic field with regular structures. Du et al. () investigated the evolution of a one-dimensional (1D) electron hole with two-dimensional (2D) electromagnetic particle-in-cell (PIC) simulations in weakly magnetized plasma (Ω< ω, where Ω and ω are the electron gyrofrequency and electron plasma frequency, respectively), which initially exists in the simulation domain. The electron hole is unstable to the transverse instability and broken into several 2D electron holes. They successfully explained the observations by THEMIS satellites based on the generated magnetic structures associated with these 2D electron holes. In this paper, 2D electromagnetic particle-in-cell (PIC) simulations are performed in the x- y plane to investigate the nonlinear evolution of the electron two-stream instability in weakly magnetized plasma, where the background magnetic field $(\mathbf{B}_{0} =B_{0}\vec{\mathbf{e}} _{x})$ is along the x direction. Several 2D electron holes are formed during the nonlinear evolution, where the parallel cuts of E and E have bipolar and unipolar structures, respectively. Consistent with the results of Du et al. (), we found that the current along the z direction is generated by the electric field drift motion of the trapped electrons in the electron holes due to the existence of E, which produces the fluctuating magnetic field δB and δB in the electron holes. The parallel cuts of δB and δB in the electron holes have unipolar and bipolar structures, respectively. [ABSTRACT FROM AUTHOR]

Magnetic reconnection provides a physical mechanism for fast energy conversion from magnetic energy to plasma kinetic energy. It is closely associated with many explosive phenomena in space plasma, usually collisionless in character. For this reason, researchers have become more interested in collisionless magnetic reconnection. In this paper, the various roles of electron dynamics in collisionless magnetic reconnection are reviewed. First, at the ion inertial length scale, ions and electrons are decoupled. The resulting Hall effect determines the reconnection electric field. Moreover, electron motions determine the current system inside the reconnection plane and the electron density cavity along the separatrices. The current system in this plane produces an out-of-plane magnetic field. Second, at the electron inertial length scale, the anisotropy of electron pressure determines the magnitude of the reconnection electric field in this region. The production of energetic electrons, which is an important characteristic during magnetic reconnection, is accelerated by the reconnection electric field. In addition, the different topologies, temporal evolution and spatial distribution of the magnetic field affect the accelerating process of electrons and determine the final energy of the accelerated electrons. Third, we discuss results from simulations and spacecraft observations on the secondary magnetic islands produced due to secondary instabilities around the X point, and the associated energetic electrons. Furthermore, progress in laboratory plasma studies is also discussed in regard to electron dynamics during magnetic reconnection. Finally, some unresolved problems are presented. [ABSTRACT FROM AUTHOR]

Electron phase space holes (electron holes) are found to be unstable to the transverse instability. Two-dimensional (2D) electromagnetic particle-in-cell simulations are performed to investigate the structures of the fluctuating magnetic field associated with electron holes. The combined actions between the transverse instability and the stabilization by the background magnetic field (B0=B0evector x) lead a one-dimensional electron hole into several 2D electron holes which are isolated in both the x and y directions. The electrons trapped in these 2D electron holes suffer the electric field drift vE=E×B0/B02 due to the existence of the perpendicular electric field Ey, which generates the current along the z direction. Then, the unipolar and bipolar structures are formed for the parallel cut of the fluctuating magnetic field along the x and y directions, respectively. At the same time, these 2D electron holes move along the x direction, and the unipolar structures are formed for the parallel cut of the fluctuating magnetic field along the z direction. [ABSTRACT FROM AUTHOR]

We perform 2.5-dimensional particle-in-cell simulations to investigate the nonlinear evolution of the lower hybrid drift instability (LHDI) in Harris current sheet. Due to the drift motion of electrons in the electric field of the excited low hybrid drift (LHD) waves, the electrons accumulate at the outer layer, and therefore there is net positive charge at the inner edge of the current sheet. This redistribution of charge can create an electrostatic field along the z direction, which then modifies the motions of the electrons along the y direction by E × B drift. This effect strongly changes the structure of the current sheet. [ABSTRACT FROM AUTHOR]

Indium gallium zinc oxide (InGaZnO) thin-film transistors (TFTs) with a co-sputtered tin indium gallium zinc oxide (SnInGaZnO) electron barrier layer (EBL) are fabricated. The effect of the SnInGaZnO layer thickness on device characteristics is investigated. With stacking a 250-nm-thick SnInGaZnO EBL in the source/drain region, it introduces an additional potential barrier of around 0.14 V to the channel carriers. Experimental results show that the turn-off voltage of TFTs increases from -0.5 V to about 0 V, the on/off current ratio increases from 1.9 × 105 to 1.9 × 106, and the subthreshold swing decreases from 0.13 V/dec to 0.073 V/dec. [ABSTRACT FROM AUTHOR]

Magnetic reconnection is considered to be one important source to produce energetic electrons. In this paper, two-dimensional (2D) particle-in-cell (PIC) simulations are performed to investigate electron acceleration during the merging process of multiple magnetic islands in a current sheet with a strong guide field. Due to the existence of the strong guide field, we can analyze the contributions of the parallel electric field, Fermi, and betatron mechanisms to the electron acceleration with the guiding-center theory. During the coalescence process of magnetic islands, the islands merge each other continuously until only one large island remains. Energetic electrons are generated during such process, and the electrons with sufficient high energy develop a power-law spectrum. We also investigate the dependence of the index of the power-law spectra on the shape of magnetic islands, electron plasma beta, the number of magnetic islands, and the guide field. [ABSTRACT FROM AUTHOR]