Search

Alfven-branch waves provide an efficient means for transporting energy into the auroral oval. Here, we report observations of these waves obtained by the Fengyun-3E (FY-3E)/ACMag instruments, which are designed to detect three-dimensional AC magnetic fields in the 0.05–25 Hz band. The observations suggest that broadband waves are a permanent feature of the auroral oval, although their amplitude and locations vary with the global state of the magnetosphere. We primarily focus on the data obtained from 10 July 2021 to 26 August 2021, during which a series of recurrent storms driven by solar wind corotating interaction regions (CIRs) occurred. Analysis of the observations shows that the auroral-oval waves grow in amplitude (1–3 orders of magnitude) and shift to lower latitude (∼10°) immediately following the decrease in the SYM-H index in each storm. Further investigation reveals the response of the auroral-oval waves has a time scale equal to or less than FY-3E's effective revisiting time, which is about 45 min. The observations presented in this paper confirm that the FY-3E/ACMag instruments provide a high-resolution monitor of the auroral-oval waves and could further our understanding of auroral physics. [ABSTRACT FROM AUTHOR]

Drift‐bounce resonance between ultralow frequency (ULF) waves and ions is essential for ion energization in the magnetosphere. Here, we present the first comprehensive study of drift‐bounce resonance in the dayside outer magnetosphere, where off‐equatorial magnetic field minima would strongly distort ions' bounce and drift motion. A generalized theory is proposed, in which the effects of off‐equatorial minima, time‐evolving fields and ion bounce motion are taken into account. In consequence of these effects, ion pitch angle distributions undergo dramatic changes. In the presence of off‐equatorial minima, the time‐of‐flight effect of ion bounce motion forms latitude‐dependent dispersions besides "paw‐track shaped" structures, while evolving wave fields cause time‐dependent phase shifts in "paw‐tracks." All the predicted signatures have been confirmed by 5 years of Magnetospheric Multiscale spacecraft data and numerical simulations. These results allow us to better understand the interactions between ULF waves and thermal ion species in global magnetospheric dynamics. Plain Language Summary: Ultralow frequency (ULF) waves are widely distributed magnetospheric waves that can efficiently accelerate particles and play important roles in geomagnetic activities. Various patterns of ULF wave‐particle interactions have been investigated in detail near the Earth. However, near the dayside boundary of the magnetosphere, the geomagnetic field changes slightly due to solar wind compression. Consequently, the interaction between ULF waves and particles is modified in this region. This study analyzes how the pattern of ULF wave‐particle interactions varies near the dayside boundary of the magnetosphere. We find the compression of the magnetic field, particle motion and ULF wave evolution change the observational signatures of ULF wave‐particle interactions in the region of interest. The results help us better understand the energy transport from the solar wind to the magnetosphere and the role of ULF waves in magnetospheric dynamics. Key Points: Ultralow frequency wave‐ion drift‐bounce resonance in the dayside outer magnetosphere is investigated with 5 years of Magnetospheric Multiscale observationsA generalized theory is proposed to explain the observed ion pitch angle evolutionThe effects of off‐equatorial minima and time‐evolving fields are taken into account successfully to depict the observations [ABSTRACT FROM AUTHOR]

The properties of an exciton in an anisotropic parabolic quantum-well wire in a magnetic field are investigated theoretically. It is found that a decrease in the confinement length increases the exciton binding energy and decreases the longitudinal extension of the exciton wave function. The results of the exciton diamagnetic shifts are in agreement with previously reported magneto-photoluminescence experimental data. Details of the effects of the magnetic field on the binding energy and the wave function of the exciton have been investigated. The conclusion is drawn that the magnetic field has a more pronounced effect in wider quantum-well wires. [ABSTRACT FROM AUTHOR]

The properties of ionized-donor-bound excitons (D+,X) in a parabolic quantum-well wire in the presence of a magnetic field are studied numerically in the framework of effective-mass envelope function theory. The binding energy of (D+,X) structures is calculated as a function of the oscillator length for different values of the magnetic field by using the one-dimensional effective potential model and the finite-difference method. The results show that the binding energy increases as the oscillator length decreases, and that it is also increased by enhancing the magnetic field. The binding energies of the complex for the two different dissociation processes are taken into account, and their behaviors are discussed in detail. The Haynes factor is found to increase rapidly with decreasing oscillator length in the case of strong parabolic potential confinement. In addition, the average interparticle distances and the probability density distributions are investigated for a given set of values of the oscillator lengths and the magnetic field. [ABSTRACT FROM AUTHOR]

The problem of a biexciton confined in parabolic GaAs quantum-well wires in the presence of a perpendicular magnetic field is discussed. We apply an analytical one-dimensional formula for the effective interaction potential between the confined charge carriers to study the binding energies of a biexciton, which results in a numerical “exactly” solvable model. The ratio of the binding energy of a biexciton to that of an exciton for a range of confinement lengths (ld) is found from 0.183 to 0.313. Magnetic field dependence of the biexciton binding energy is also investigated and it is found that the influence is stronger when the confinement length is larger. [ABSTRACT FROM AUTHOR]

The ground state of a negatively charged donor (D-) in a parabolic GaAs quantum-well wire in the presence of a magnetic field is investigated using the finite difference method within the quasi-one-dimensional effective potential model. The magnetic effects on the binding energies of the ground state of a D- center are calculated for various parabolic potentials. The distance between the electrons and the donor ion and the distance between the two electrons are also calculated, respectively, as a function of the strength of the parabolic potential and the magnetic field. We find that the interplay of the spatial confinement and the magnetic confinement of electrons in quantum-well wires leads to complicated behavior of the binding energies of the D- center and that the increase of the electron-donor ion attraction dominates the increase of the electron-electron repulsion as the spatial and magnetic confinement increases for the ground state of a D- center in a parabolic quantum-well wire. [ABSTRACT FROM AUTHOR]

We report the binding energies of a hydrogenic-donor impurity in a cylindrically symmetric GaAs/Ga1-xAlxAs-coupled quantum disk in the presence of a uniform magnetic field for different disk and barrier thicknesses, disk radii, and donor ion positions within the disk. The magnetic field is assumed to be applied parallel to the disk axis. The calculations were performed using a variational procedure for finite-confinement potentials within the effective-mass approximation. The calculated results show that the binding energy is dependent on the interplay of the spatial confinement and magnetic-field confinement: A high magnetic field significantly enhances the binding energy in the case of weak spatial confinement. The binding energy of a hydrogenic-donor impurity in two coupled quantum disks is found to be smaller than that in a corresponding single quantum disk, due to the coupling effect between the disks. In the limits of coupled quantum wells, the results we obtain are in good agreement with those previously obtained for the case in which the donor ion is located at the center of the quantum disk. [ABSTRACT FROM AUTHOR]

Calculates the effect of a spatially dependent effective mass in a finite GaAs/Al[sub x]Ga[sub 1-x]As parabolic quantum well with a magnetic field on hydrogenic impurity ground state binding energies and lowly excited state. Comparison of the results with square quantum wells and without the effect of spatially dependent effective mass result.

We study theoretically the essential properties of an exciton in vertically coupled Gaussian quantum dots in the presence of an external magnetic field. The ground state energy of a heavy-hole exciton is split into four energy levels due to the Zeeman effect. For the symmetrical system, the entanglement entropy of the exciton state can reach a value of 1. However, for a system with broken symmetry, it is close to zero. Our results are in good agreement with previous studies. [ABSTRACT FROM AUTHOR]

The binding energy of a hydrogenic impurity in self-assembled double quantum dots is calculated via the finitedifference method. The variation in binding energy with donor position, structure parameters and external magnetic field is studied in detail. The results found are: (i) the binding energy has a complex behaviour due to coupling between the two dots; (ii) the binding energy is much larger when the donor is placed in the centre of one dot than in other positions; and (iii) the external magnetic field has different effects on the binding energy for different quantum-dot sizes or lateral confinements. [ABSTRACT FROM AUTHOR]

Abstract: Using transfer matrix method, transport properties in graphene based double velocity-barrier structures under magnetic and electric fields are numerically studied. It is found that velocity barriers for the velocity ratio (the Fermi velocity inside the barrier to that outside the barrier) less than one (or for the velocity ratio greater than one) have properties similar to electrostatic wells (or barriers). The velocity barriers for the velocity ratio greater than one significantly enlarge the resonant tunneling region of electrostatic barriers. In the presence of magnetic field, the plateau width of the Fano factor with a Poissonian value shortens (or broadens) for the case of the velocity ratio less than one (or greater than one). When the Fermi energy is equal to the electrostatic barrier height, for different values of the velocity ratio, both the conductivities and the Fano factors remain fixed. [Copyright &y& Elsevier]

Abstract: Within the effective-mass approximation we calculate the energies of a donor impurity in an elliptical quantum ring subjected to a magnetic field. The energies are found to exhibit Aharonov–Bohm oscillations depending on the magnetic field and the eccentricity. As the eccentricity increases, the energies decrease and the period increases. [Copyright &y& Elsevier]

Using standard quantum network method, we analytically investigate the effect of Rashba spin–orbit coupling (RSOC) and a magnetic field on the spin transport properties of a polygonal quantum ring. Using Landauer–Büttiker formula, we have found that the polarization direction and phase of transmitted electrons can be controlled by both the magnetic field and RSOC. A device to generate a spin-polarized conductance in a polygon with an arbitrary number of sides is discussed. This device would permit precise control of spin and selectively provide spin filtering for either spin up or spin down simply by interchanging the source and drain. [ABSTRACT FROM AUTHOR]