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  • 1
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    Acceleration of thermal plasma in the magnetosphere (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Analytic theory and numerical simulations are used here to investigate the physics of two types of mixed plasmas. The transverse acceleration of ions on auroral field lines is considered in order to determine the effects of multiion species. In the auroral zone the components of a multiion plasma, including hydrogen and oxygen, interact with each other as well as with a two-component electron plasma composed of both a magnetospheric beam and background ionospheric components. This interaction occurs as a mixed ion-ion hybrid mode. How an electron plasma, with both hot and cold components as well as ion beams, affects the plasma sheet boundary layer is examined. It is found that in the presence of this mixed electron plasma, warm ion beams can drive the electron acoustic instability; this phenomenon may be responsible for broadband electrostatic noise in the boundary layer.
    Keywords: GEOPHYSICS
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  • 2
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    A global magnetohydrodynamic simulation of magnetospheric dynamics when the IMF is southward: Mapping to the auroral zone (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A high resolution global magnetohydrodynamic simulation model is used to investigate magnetospheric dynamics during intervals with southward interplanetary magnetic field (IMF). When the southward IMF reaches the dayside magnetopause reconnection begins and magnetic flux is convected into the tail lobes. After about 35 m, reconnection begins within the plasma sheet near midnight at x = -14 RE. Later the x-line moves towards the magnetopause. The reconnection occurs just tailward of the region where the tail attaches onto the dipole dominated inner magnetosphere. Later when all the plasma sheet field lines have reconnected a plasmoid moves down the tail. The region of the ionosphere where the energy flux from the magnetosphere is greatest is calculated. The energy flux is confined to a region which approximates the auroral oval.
    Keywords: GEOPHYSICS
    Type: ESA, Substorms 1; p 571-576
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  • 3
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    Effects of near-Earth stochastic acceleration and reflections of magnetotail ions on the formation of auroral arcs (1992)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Findings obtained from global kinetic simulations of magnetotail plasma are discussed. A region of strongly nonadiabatic ion acceleration (known as the 'wall' region) exists in the near earth tail and demarcates two very different regimes of ion motion: adiabatic and quasi-adiabatic. After convection through the wall, ion distributions rapidly become isotropized and thermalized. A strong enhancement of the cross tail current occurs on the tailward side of the wall. Comparison of numerical and adiabatic pressure profiles indicates that nonadiabatic processes operating in this region may contribute significantly to a pressure balance relief in the course of quasi-steady magnetospheric convection.
    Keywords: GEOPHYSICS
    Type: ESA, Substorms 1; p 545-552
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  • 4
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    Propagation of beam-driven VLF waves from the ionosphere toward the ground (1995)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: As part of the Cooperative High Altitude Rocket Gun Experiment (CHARGE-2B) rocket mission, an electron beam was injected into the ionosphere with a modulated beam current in an effort to generate very low frequency (VLF) waves. The propagation of the beam-driven VLF waves through the ionosphere is examined here to determine whether it is possible to detect these wave emissions with ground receivers. The paths of the VLF waves from where they were generated near the rocket were followed to the bottom of the ionosphere and the decrease in wave amplitude due to wave-particle resonance and collisional damping was calculated. It was found that due to collisional damping, which for these VLF waves becomes large at altitudes below about 150 km, wave amplitudes were decreased below the background atmospheric noise level. A number of different beam injection events have been examined and in all of these cases studied the waves were sufficiently damped such that detection on the ground would not be possible. This is in agreement with observations on the ground in which no wave emissions were observed during the CHARGE-2B mission. Control parameters that would be more favorable for beam-generated VLF propagation to the ground are discussed for future experiments of this type.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A3; p. 3693-3702
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  • 5
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    Magnetic flux ropes at the high-latitude magnetopause (1995)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We examine the consequences of magnetic reconnection at the high-latitude magnetopause using a three-dimensional global magnetohydrodynamic simulation of the solar wind interaction with the Earth's magnetosphere. Magnetic field lines from the simulation reveal the formation of magnetic flux ropes during periods with northward interplanetary magnetic field. These flux ropes result from multiple reconnection processes between the lobes field lines and draped magnetosheath field lines that are convected around the flank of the magnetosphere. The flux ropes identified in the simulation are consistent with features observed in the magnetic field measured by Hawkeye-1 during some high-latitude magnetopause crossings.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 10; p. 1189-1192
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  • 6
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    Simulation of magnetic field line stochasticity at the magnetopause (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We have conducted a three-dimensional particle simulation to study the magnetic field line stochasticity at the magnetopause current layer. Our results show that the magnetic field lines become stochastic due to the overlap of the destabilized multiple tearing mode islands, which agrees with the percolation model suggested by Galeev et al. (1986). After the field lines become stochastic, these tearing modes grow even 2-3 times faster than in the linear stage and saturate at an amplitude level 3-4 times bigger than the single tearing mode without mode-mode coupling. The field line stochasticity also causes a strong particle diffusion across the current layer. The diffusion coefficient reaches to 10(exp 9) sq m/s for typical magnetopause parameters. Associated with the particle diffusion, the current layer becomes broader in width. As a result, the magnetic energy is dissipated into particle energy by heating parallel to the local magnetic field. The particle energy increases by 60%, while the magnetic helicity, which has always been regarded as a good invariant, changes by 20%.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A2; p. 2321-2334
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  • 7
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    The formation of the wall region - Consequences in the near earth magnetotail (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This paper discusses important new findings obtained from global kinetic simulations of magnetotail plasma. A region of strongly nonadiabatic ion acceleration (known as the wall region) exists in the near earth tail and demarcates two very different regimes of ion motion: adiabatic and quasi-adiabatic. A strong enhancement of the cross-tail current occurs on the tailward side of the wall. A comparison of numerical and adiabatic pressure profiles indicates that nonadiabatic processes operating in this region may contribute significantly to a pressure balance relief in the course of quasi-steady magnetospheric convection.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 17 S; 1739-174
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  • 8
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    Electron velocity space hole modes and narrowband electrostatic noise in the distant tail (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Narrowband electrostatic noise (NEN) is frequently observed upstream of the slow shocks in the distant tail. It is suggested that NEN represents a nonstandard plasma wave mode which results from a hole in the low energy electron velocity distribution. A very simple model which plausibly indicates how a hole might be formed by the interaction of the electrons with the slow shock is presented. The hole mode is destabilized by a positive slope in the parallel electron distribution and/or by a weak beam of energetic ions which escape upstream from the slow shock.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 747-750
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  • 9
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    The coalescence of magnetic flux ropes and reconnection in the magnetotail (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2471-248
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  • 10
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    A theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion conics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 21-24
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