Search

Your search keyword '"Dawson, J. M."' showing total 619 results
Start Over Author "Dawson, J. M."
619 results on '"Dawson, J. M."'

51. Global simulations of the three-dimensional magnetosphere

Author

Leboeuf, J. N, Tajima, T, Kennel, C. F, and Dawson, J. M

Subjects
Geophysics
Abstract

Global three-dimensional computer simulations of the magnetosphere using a particle MHD code, reproduce the steady-state Dungey magnetospheric topology in three dimensions. The formation of a compression zone downstream of the tail neutral line that is probably bounded by wake shocks is observed. This compression zone changes its cross-section with distance downstream.

Published
1981

52. Simulation of space plasma phenomena

Author

Dawson, J. M

Subjects
Physics (General)
Abstract

The importance of computer modeling in investigating physical phenomena is discussed, noting that modern computers can follow the time evolution of systems containing many millions of degrees of freedom, all of which are simultaneously interacting with each other. The two types of models used in simulating plasma, that is, particle and fluid, are described. Attention is given to particle models and some recent results obtained concerning the diffuse aurora. The simulations are shown to give clear evidence that a type of nonlinear cyclotron resonance process for the cold particles is responsible for the saturation observed in these calculations. It is also responsible for the cold electron heating and it is found that at saturation the rate of heating of the cold electrons essentially balances the rate at which energy is fed into unstable waves.

Published
1981

53. A simulation study of cold electron heating by loss cone instabilities

Author

Ashour-Abdalla, M, Leboeuf, J. N, Dawson, J. M, and Kennel, C. F

Subjects
Geophysics
Abstract

Results are presented of a computer simulation study of electron cyclotron harmonic waves; an electrostatic finite size particle simulation code is used. The initial electron velocity distribution function is modeled as a hot ring perpendicular to the ambient magnetic field and a cold Maxwellian component. Nonlinear cyclotron resonance is found to be the saturation mechanism of the unstable waves and the heating mechanism of the cold electrons. The results can be related to certain ionospheric phenomena.

Published
1980

54. Global magnetohydrodynamic simulation of the two-dimensional magnetosphere

Author

Leboeuf, J. N, Tajima, T, Kennel, C. F, and Dawson, J. M

Subjects
Geophysics
Abstract

The time-dependent magnetohydrodynamic interaction of the solar wind with a two-dimensional dipole magnetic field has been simulated using a novel Lagrangian particle type of MHD code that can treat local low density or vacuum regions without numerical instability. This enables one to simulate the time-dependent magnetic tail. When the solar wind field is southward, a magnetic field line topology consistent with Dungey's model emerges in steady state. The tail, however, is short, and the x-points are only slightly shifted from their vacuum locations, because of strong numerical resistivity. Different configurations resulting from different relative orientations of the solar wind magnetic field and dipole axis are also presented. While the magnetic field is relatively steady, the density and flow in the magnetosheath are turbulent, as are the bow shock and magnetopause; the Kelvin-Helmholtz instability may account for these phenomena. We also model a 'substorm' as the passage of a rotational discontinuity in the solar wind over the dipole. Both 90 and 180 deg shifts to a southward solar wind field cause a violent readjustment of the magnetic tail which eventually settles down to the Dungey configuration.

Published
1979

55. Global simulation of the time-dependent magnetosphere

Author

Leboeuf, J. N, Tajima, T, Kennel, C. F, and Dawson, J. M

Subjects
Geophysics
Abstract

The paper presents preliminary results from time-dependent two-dimensional numerical modelling of the magnetohydrodynamic interaction of the solar wind with the magnetosphere. A southward solar wind-field produces a magnetospheric topology consistent with Dungey's (1961) model. The interaction appears to be fundamentally unsteady; the shock, magnetosheath, and magnetopause are highly turbulent. A 'substorm' is modelled as the passage of a rotational discontinuity over the magnetosphere; the onset of enhanced reconnection in the magnetospheric tail produces a closed magnetic island which convects downstream.

Published
1978

83. Proceedings of the International Workshop on Acceleration and Radiation Generation in Space and Laboratory Plasmas Held in Kardamyli, Greece on 29 Aug-4 Sep 93.

Author

UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF ELECTRICAL ENGINEERING, Bingham, R., Dawson, J. M., Katsouleas, T., Stenflo, L., UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF ELECTRICAL ENGINEERING, Bingham, R., Dawson, J. M., Katsouleas, T., and Stenflo, L.

Abstract

Workshop proceedings-Papers presented at the International Workshop on Acceleration and Radiation Generation in Space and Laboratory. Plasmas Kardamyli, Greece, August 29 - September 4, 1993.

Published
1995

Catalog

Books, media, physical & digital resources
See catalog results