TIME-DEPENDENT CALCULATION FOR THE TRANSMISSION COEFFICIENT OF TWO-DIMENSIONAL QUANTUM WIRE STRUCTURES IN THE PRESENCE OF MAGNETIC FIELD

1999 ◽  
Vol 13 (08) ◽  
pp. 895-902
Author(s):  
CHINGHONG YIU ◽  
JIAN WANG
Keyword(s):  
Magnetic Field ◽  
Transmission Coefficient ◽  
Time Evolution ◽  
Quantum Wire ◽  
Arbitrary Shape ◽  
Wave Functions ◽  
Time Dependent ◽  
Mode Matching ◽  
Two Dimensional ◽  
Matching Method

We present a simple and efficient method for calculating transmission coefficient of two-dimensional quantum wire structures in the presence of magnetic field. The time evolution of a wave packet is first obtained by solving the time dependent Schrödinger equation. Transmission coefficient is then extracted from the wave function by an intergal transform. This method is easier to implement than traditional time-independent methods such as mode matching method and it can be used to study the time evolution of wave functions for systems with arbitrary shape.

scholarly journals LION: A dynamic computer model for the low-latitude ionosphere

2007 ◽  
Vol 25 (11) ◽  
pp. 2371-2392 ◽  
Author(s):  
J. A. Bittencourt ◽  
V. G. Pillat ◽  
P. R. Fagundes ◽  
Y. Sahai ◽  
A. A. Pimenta
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Computer Model ◽  
Transport Processes ◽  
Time Dependent ◽  
Low Latitude ◽  
Radiation Chemical ◽  
Neutral Winds ◽  
Plasma Drifts ◽  
Low Latitude Ionosphere

Abstract. A realistic fully time-dependent computer model, denominated LION (Low-latitude Ionospheric) model, that simulates the dynamic behavior of the low-latitude ionosphere is presented. The time evolution and spatial distribution of the ionospheric particle densities and velocities are computed by numerically solving the time-dependent, coupled, nonlinear system of continuity and momentum equations for the ions O+, O2+, NO+, N2+ and N+, taking into account photoionization of the atmospheric species by the solar extreme ultraviolet radiation, chemical and ionic production and loss reactions, and plasma transport processes, including the ionospheric effects of thermospheric neutral winds, plasma diffusion and electromagnetic E×B plasma drifts. The Earth's magnetic field is represented by a tilted centered magnetic dipole. This set of coupled nonlinear equations is solved along a given magnetic field line in a Lagrangian frame of reference moving vertically, in the magnetic meridian plane, with the electromagnetic E×B plasma drift velocity. The spatial and time distribution of the thermospheric neutral wind velocities and the pattern of the electromagnetic drifts are taken as known quantities, given through specified analytical or empirical models. The model simulation results are presented in the form of computer-generated color maps and reproduce the typical ionization distribution and time evolution normally observed in the low-latitude ionosphere, including details of the equatorial Appleton anomaly dynamics. The specific effects on the ionosphere due to changes in the thermospheric neutral winds and the electromagnetic plasma drifts can be investigated using different wind and drift models, including the important longitudinal effects associated with magnetic declination dependence and latitudinal separation between geographic and geomagnetic equators. The model runs in a normal personal computer (PC) and generates color maps illustrating the typical behavior of the low-latitude ionosphere for a given longitudinal region, for different seasons, geophysical conditions and solar activity, at each instant of time, showing the time evolution of the low-latitude ionosphere, between about 20° north and south of the magnetic equator. This paper presents a detailed description of the mathematical model and illustrative computer results.

ON AXIALLY SYMMETRIC ELECTRIC CURRENT INDUCED IN A CYLINDER UNDER A LINE SOURCE

Geophysics ◽  
1973 ◽  
Vol 38 (5) ◽  
pp. 971-974 ◽  
Author(s):  
Shri Krishna Singh
Keyword(s):  
Magnetic Field ◽  
Electric Current ◽  
Short Note ◽  
Cylindrical Wave ◽  
Wave Functions ◽  
Static Case ◽  
Two Dimensional ◽  
Dimensional Problem ◽  
Axially Symmetric ◽  
Infinite Line

An infinite conducting cylinder excited by an infinite line current located outside the cylinder is a useful model in the interpretation of electromagnetic prospecting data. Several authors, with geophysical applications in mind, have considered the problem of the source being parallel to the axis of the cylinder (Wait, 1952; Negi et al., 1972). In the latter paper, the cylinder is surrounded by a shell; conductivity of both the cylinder and the shell is a function of radius. The secondary fields are written in the form of an infinite series of cylindrical wave functions. This solution is then specialized to the quasi‐static case. For reasons not explained, the authors neglect the n = 0 term. In this short note, computed results are presented which show that the contribution from the n = 0 term (corresponding to an axially symmetric electric current induced in the cylinder causing a transverse secondary magnetic field outside) is significant and must be taken into account for the two‐dimensional problem.

FERMIONIC FOUR-LEVEL SYSTEM IN THE PRESENCE OF A TIME-DEPENDENT MAGNETIC FIELD

1996 ◽  
Vol 10 (14) ◽  
pp. 643-651 ◽  
Author(s):  
M.T. THOMAZ
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Thermal Equilibrium ◽  
Initial Conditions ◽  
Time Dependent ◽  
Initial Vector ◽  
Vector State ◽  
Level System ◽  
Exact Time

The exact fermionic four-level system is studied in the presence of time-dependent magnetic field. The system is considered under two initial conditions: general initial vector state, and, at thermal equilibrium. The exact time evolution of one-particle operators is derived.

Convection in an imposed magnetic field. Part 2. The dynamical regime

1981 ◽  
Vol 108 ◽  
pp. 273-289 ◽  
Author(s):  
N. O. Weiss
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Thermal Diffusivity ◽  
Large Scale ◽  
Time Dependent ◽  
Dynamical Regime ◽  
Two Dimensional ◽  
Chandrasekhar Number ◽  
Steady Convection ◽  
Active Flux

Nonlinear, two-dimensional magnetoconvection has been investigated numerically for a fixed Rayleigh number of 104, with the ratio ζ of the magnetic to the thermal diffusivity in the range 0·4 ≥ ζ ≥ 0·05. As the Chandrasekhar number Q is decreased, convection first sets in as overstable oscillations, which are succeeded by steady convection with dynamically active flux sheets and, eventually, with kinematically concentrated fields. In the dynamical regime spatially asymmetrical convection, with most of the flux on one side of the cell, is preferred. As Q increases, these asymmetrical solutions become time-dependent, with oscillations about the steady state which develop into large-scale oscillations with reversals of the flow. Although linear theory predicts that narrow cells should be most unstable, the nonlinear results show that steady convection occurs most easily in cells that are roughly twice as wide as they are deep.

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