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  • 1
    Electronic Resource
    Electronic Resource
    Particle acceleration in the dynamic magnetotail : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 2149-2156 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The acceleration of charged particles to suprathermal energies is investigated in the context of magnetospheric substorms. Ion and electron test particle orbits are studied in dynamically evolving fields obtained from a three-dimensional resistive magnetohydrodynamic (MHD) simulation of reconnection in the near magnetotail. The simulation leads to plasmoid formation and ejection into the distant tail and an earthward collapse of the field in the inner tail. Energization of particles takes place predominantly in the inner tail region earthward of the neutral line, rather than in the vicinity of the neutral line. The test particle studies reproduce major observed characteristics of energetic particle flux increases ("injections") in the inner magnetotail; a fast rise, a limited energy range of the flux increases, and spatially varying delays between the onsets of ion and electron injections. Acceleration mechanisms include a "quasipotential" acceleration, resulting from nonadiabatic particle motion in the direction of the cross-tail electric field, as well as betatron and Fermi-type acceleration. The major source region for accelerated ions (electrons) in the hundreds of keV range is the central plasma sheet at the dawn (dusk) flank, outside the reconnection site. Since this source plasma is already hot and dense, a moderate energization by a factor of approximately 2 is sufficient to explain the observed increases in the energetic particle fluxes. Differences between ions and electrons at energies of a few tens of keV are found to be associated with differences in the bounce periods, which enables ions to circumvent the acceleration region, so that only electron fluxes in that energy range become enhanced. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874035
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  • 2
    Electronic Resource
    Electronic Resource
    Stretched three-dimensional plasma equilibria with field-aligned flow (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 479-484 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A three-dimensional equilibrium theory [J. Geophys. Res. 92, 11 101 (1987)] for stretched plasma configurations, such as the Earth's magnetotail, is extended to include the effects of field-aligned flow. The magnetohydrodynamic (MHD) equations for this case can be solved in a general way by reduction to a set of ordinary differential equations and an ordinary integral. The solutions represent lowest-order solutions of an asymptotic expansion of the MHD equations for small electric field and weak time dependence. Simplified equations are presented for two-dimensional equilibria and for incompressible flow. Possible magnetospheric applications include the configuration of the geotail near and beyond the termination of the closed field line region, the steady motion of a plasmoid (a plasma bubble severed from the Earth) through the distant geotail, and configurations at the magnetopause, the interface between the magnetosphere and the shocked solar wind plasma. For illustration, solutions for the steady motion of a two-dimensional plasmoid through the distant magnetotail are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859891
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  • 3
    Electronic Resource
    Electronic Resource
    The electric field and plasma energization in computer simulations of magnetotail reconnection
    Amsterdam : Elsevier
    Advances in Space Research 4 (1984), S. 449-458 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(84)90345-4
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  • 4
    Electronic Resource
    Electronic Resource
    Parallel electric fields as acceleration mechanisms in three-dimensional magnetic reconnection
    Amsterdam : Elsevier
    Advances in Space Research 13 (1993), S. 249-252 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(93)90341-8
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  • 5
    Electronic Resource
    Electronic Resource
    Particle acceleration in a MHD simulation of magnetotail dynamics
    Amsterdam : Elsevier
    Advances in Space Research 13 (1993), S. 245-248 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(93)90340-H
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetospheric physics
    Amsterdam : Elsevier
    Physics Reports 47 (1978), S. 109-165 
    Details
    ISSN: 0370-1573
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0370-1573(78)90016-9
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  • 7
    Electronic Resource
    Electronic Resource
    Substorm observations in the early morning sector with Equator-S and Geotail (1999)
    Springer
    Annales geophysicae 17 (1999), S. 1602-1610 
    Details
    ISSN: 0992-7689
    Keywords: Magnetospheric physics (magnetospheric configuration and dynamics ; plasma sheet ; storms and substorms)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Data from Equator-S and Geotail are used to study the dynamics of the plasma sheet observed during a substorm with multiple intensifications on 25 April 1998, when both spacecraft were located in the early morning sector (03–04 MLT) at a radial distance of 10–11 RE. In association with the onset of a poleward expansion of the aurora and the westward electrojet in the premidnight and midnight sector, both satellites in the morning sector observed plasma sheet thinning and changes toward a more tail-like field configuration. During the subsequent poleward expansion in a wider local time sector (20−04 MLT), on the other hand, the magnetic field configuration at both satellites changed into a more dipolar configuration and both satellites encountered again the hot plasma sheet. High-speed plasma flows with velocities of up to 600 km/s and lasting 2–5 min were observed in the plasma sheet and near its boundary during this plasma sheet expansion. These high-speed flows included significant dawn-dusk flows and had a shear structure. They may have been produced by an induced electric field at the local dipolarization region and/or by an enhanced pressure gradient associated with the injection in the midnight plasma sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-1602-3
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  • 8
    Electronic Resource
    Electronic Resource
    Open and closed magnetospheric tail configurations and their stability (1975)
    Springer
    Astrophysics and space science 35 (1975), S. 389-402 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The asymptotic theory valid for magnetospheric tail configurations that vary only weakly in the antisolar direction is used to derive a number of explicit properties. The conditions under which the magnetopause converges to form a closed magnetosphere or diverges (open magnetosphere) are identified and discussed. It is shown that the presence of the high latitude low pressure tail lobes guarantees the open solution. The large value of the Mach-number of the unperturbed solar wind is the reason for the slow variation of the plasma and field quantities along the tail. Criteria for (two-dimensional) stability are discussed and it is shown that they can be expressed in terms of simple topological properties of the equilibria. Closed magnetopheres turn out to be stable, open magnetospheres with sufficiently stretched field lines are subject to an instability which — as shown earlier —may be the cause of magnetospheric substorms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637005
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetotail theory (1986)
    Springer
    Space science reviews 44 (1986), S. 307-355 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper reviews present theory of the structure and the dynamics of the Earth's magnetotail. Since dynamical phenomena occur on different length and time-scales it seems appropriate to begin with comments on plasma models. Then it is argued that any successful theory of the rapid dynamic processes observed in the magnetotail requires a detailed analysis of the quiet states and their slow evolution. Accordingly, we present a rather detailed description of corresponding theoretical work. A major result is that under conditions that seem to be realistic for periods of southward-pointing interplanetary magnetic field, extended magnetotail flux tubes must evolve in time such that energy is slowly built up in the tail. Magnetic reconnection at a distant neutral line seems to be a natural cause of the high speed plasma flows observed near the boundary of the plasma sheet. These results then raise the problem of stability of the magnetotail. It is argued that non-ideal plasma processes must be involved in any instability mechanism that is able to explain the onset of the fast dynamic phases. Since the nature of the relevant non-ideal effect (or effects) is not yet identified, several possibilities are discussed, namely, ion-inertial effects, resistive magnetohydrodynamic evolution and non-resistive relaxation. It is an interesting fact that all three approaches, although substantially different, lead to qualitatively similar unstable magnetic field patterns. Two of the major aspects involved are magnetic reconnection and the formation of plasmoids. On the basis of the theoretical results available both for quiet and dynamic states, a unified picture emerges is able to explain major observational features in terms of physical processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00200819
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  • 10
    Electronic Resource
    Electronic Resource
    The evolution of line-tied coronal arcades including a converging footpoint motion (1992)
    Springer
    Solar physics 138 (1992), S. 257-281 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It has been demonstrated in the past that single, two-dimensional coronal arcades are very unlikely driven unstable by a simple shear of the photospheric footpoints of the magnetic field lines. By means of two-dimensional, time-dependent MHD simulations, we present evidence that a resistive instability can result if in addition to the footpoint shear a slow motion of the footpoints towards the photospheric neutral line is included. Unlike the model recently proposed by van Ballegooijen and Martens (1989), the photospheric footpoint velocity in our model is nonsingular and the shear dominates everywhere. Starting from a planar potential field geometry for the arcade, we find that after some time a current sheet is formed which is unstable with respect to the tearing instability. The time of its onset scales with the logarithm of the magnetic diffusivity assumed in our calculation. In its nonlinear phase, a quasi-stationary situation arises in the vicinity of the x-line with an almost constant reconnection rate. The height of the x-line above the photosphere and the distance of the separatrix footpoints remain almost constant in this phase, while the helical flux tube, formed above the neutral line, continuously grows in size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151915
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