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.

scholarly journals Modification of conductivity due to acceleration of the ionospheric medium

2008 ◽  
Vol 26 (8) ◽  
pp. 2111-2130 ◽  
Author(s):  
V. V. Denisenko ◽  
H. K. Biernat ◽  
A. V. Mezentsev ◽  
V. A. Shaidurov ◽  
S. S. Zamay
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Electric Current ◽  
Magnetic Field Line ◽  
Conducting Layer ◽  
Low Latitude ◽  
Ionosphere Model ◽  
Zero Current ◽  
Night Side ◽  
Low Latitude Ionosphere

Abstract. A quantitative division of the ionosphere into dynamo and motor regions is performed on the base of empirical models of space distributions of ionospheric parameters. Pedersen and Hall conductivities are modified to represent an impact of acceleration of the medium because of Ampére's force. It is shown that the currents in the F2 layer are greatly reduced for processes of a few hours duration. This reduction is in particular important for the night-side low-latitude ionosphere. The International Reference Ionosphere model is used to analyze the effect quantitatively. This model gives a second high conducting layer in the night-side low-latitude ionosphere that reduces the electric field and equatorial electrojets, but intensifies night-side currents during the short-term events. These currents occupy regions which are much wider than those of equatorial electrojets. It is demonstrated that the parameter σd=σP+σHΣH/ΣP that involves the integral Pedersen and Hall conductances ΣP, ΣH ought to be used instead of the local Cowling conductivity σC in calculations of the electric current density in the equatorial ionosphere. We may note that Gurevich et al. (1976) derived a parameter similar to σd for more general conditions as those which we discuss in this paper; a more detailed description of this point is given in Sect. 6. Both, σd and σC, appear when a magnetic field line is near a nonconducting domain which means zero current through the boundary of this domain. The main difference between σd and σC is that σd definition includes the possibility for the electric current to flow along a magnetic field line in order to close all currents which go to this line from neighboring ones. The local Cowling conductivity σC corresponds to the current closure at each point of a magnetic field line. It is adequate only for a magnetic field line with constant local conductivity at the whole line when field-aligned currents do not exist because of symmetry, but σC=σd in this case. So, there is no reason to use the local Cowling conductivity while the Cowling conductance ΣC=ΣP+ΣH2/ΣP is a useful and well defined parameter.

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.

scholarly journals On the response of the equatorial and low latitude ionospheric regions in the Indian sector to the large magnetic disturbance of 29 October 2003

2009 ◽  
Vol 27 (6) ◽  
pp. 2539-2544 ◽  
Author(s):  
G. Manju ◽  
T. Kumar Pant ◽  
S. Ravindran ◽  
R. Sridharan
Keyword(s):  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Equatorial Station ◽  
Neutral Winds ◽  
Storm Sudden Commencement ◽  
Magnetometer Data ◽  
Ionospheric Height ◽  
Electric Field Penetration ◽  
Low Latitude Ionosphere

Abstract. The present paper investigates the response of the equatorial and low latitude ionosphere over the Indian longitudes to the events on 29 October 2003 using ionosonde data at Trivandrum (8.5° N (0.5° N geomagnetic), 77° E) and SHAR (13.7° N (5.7° N geomagnetic), 80.2° E), ground-based magnetometer data from Trivandrum and Total Electron Content (TEC) derived from GPS data at the locations of Ahmedabad (23° N (15° N geomagnetic), 72° E), Jodhpur (26.3° N (18.3° N geomagnetic), 73° E) and Delhi (28° N (20° N geomagnetic), 77° E). Following the storm sudden commencement, the TEC at all the three stations showed an overall enhancement in association with episodes of inter-planetary electric field penetration. Interestingly, real ionospheric height profiles derived using the ionosonde data at both Trivandrum and SHAR showed significant short-term excursions and recoveries. In the post noon sector, these features are more pronounced over SHAR, an off equatorial station, than those over Trivandrum indicating the increased effects of neutral winds.

SPATIAL ROTATION AND TIME-EVOLUTION OPERATOR OF TWO-LEVEL SYSTEMS

2000 ◽  
Vol 14 (01) ◽  
pp. 101-112
Author(s):  
CHUN-FANG LI ◽  
XIAN-GENG ZHAO
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Evolution Operator ◽  
Order Differential Equation ◽  
Time Dependent ◽  
Time Varying ◽  
Level System ◽  
Zener Model ◽  
Time Evolution Operator ◽  
Two Level Systems

All the six kinds of rotation approach with the same form to the evolution problem of arbitrarily time-dependent two-level system are investigated in this paper. A time-dependent two-level system can be viewed as a spin-1/2 system in a time-varying magnetic field. It is shown that for each kind of rotation approach, we can always find a rotating frame in which the direction of the effective magnetic field is fixed. This property reduces the problem of finding the time-evolution operator to the solution of a second-order differential equation. Applications are made to the J C model in quantum optics and the L and au–Zener model in resonance physics.

SPIN CLUSTER AS A QUBIT: ROBUST AGAINST DISSIPATION OF THERMAL RADIATION FIELDS

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2481-2485 ◽  
Author(s):  
XIAO-FEI SU ◽  
SHUN-JIN WANG
Keyword(s):  
Magnetic Field ◽  
Thermal Radiation ◽  
Time Evolution ◽  
Logic Gate ◽  
Time Dependent ◽  
Body System ◽  
Many Body ◽  
Spin Cluster ◽  
Radiation Fields ◽  
Qubit System

A spin cluster of 3 spin 1/2 particles has been studied as a qubit system. A time dependent magnetic field is applied to control the time evolution of the cluster. The lowest energy level of the cluster has the total spin 1/2 separated far away from the excited states and can be used as a qubit register. The universal 1-qubit logic gate can be constructed from the time evolution operator of the non-autonomous many-body system, and the 6 basic 1-qubit gates can be realized by adjusting the applied time dependent magnetic field. As a many-body system, this qubit system is expected to be robust against the dissipation effect of the thermal radiation fields from the environment.

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