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  • 1
    Electronic Resource
    Electronic Resource
    Analytic solutions of the magnetic annihilation and reconnection problems. II. Three-dimensional flows (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 110-119 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analytic solutions for magnetic annihilation and reconnection in three-dimensional velocity fields are constructed. Exact and approximate solutions for three-dimensional fan current reconnection can be derived using prototype fields based on simple, one-component magnetic annihilation models. Certain reconnection solutions are found to be "fast," in the sense that the Ohmic dissipation rate scales independently of any positive power of the plasma resistivity η. Three-dimensional models can also possess novel features not contained in two-dimensional planar reconnection solutions. In particular, classes of solutions involving separated field nulls are found to possess multiple scalings for the Ohmic dissipation rate—a feature that has not been observed before. Several solutions are shown to have the potential to meet the extreme energy release characteristics of the solar flare. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872121
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  • 2
    Electronic Resource
    Electronic Resource
    Analytic solutions of the magnetic annihilation and reconnection problems. I. Planar flow profiles (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 101-109 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phenomena of steady-state magnetic annihilation and reconnection in the vicinity of magnetic nulls are considered. It is shown that reconnective solutions can be derived by superposing the velocity and magnetic fields of simple magnetic annihilation models. These solutions contain most of the previous models for magnetic merging and reconnection, as well as introducing several new solutions. The various magnetic dissipation mechanisms are classified by examining the scaling of the Ohmic diffusion rate with plasma resistivity. Reconnection solutions generally allow more favorable "fast" dissipation scalings than annihilation models. In particular, reconnection models involving the advection of planar field components have the potential to satisfy the severe energy release requirements of the solar flare. The present paper is mainly concerned with magnetic fields embedded in strictly planar flows—a discussion of the more complicated three-dimensional flow patterns is presented in Part II [Phys. Plasmas 4, 110 (1997)]. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872569
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamic magnetic reconnection in three space dimensions: Fan current solutions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 635-644 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of incompressible, nonlinear magnetic reconnection in three-dimensional "open" geometries is considered. An analytic treatment shows that dynamic "fan current" reconnection may be driven by superposing long wavelength, finite amplitude, plane wave disturbances onto three-dimensional magnetic X-points. The nonlinear reconnection of the field is preceded by an advection phase in which magnetic shear waves drive large currents as they localize in the vicinity of the magnetic null. Analytic arguments, reinforced by detailed simulations, show that the ohmic dissipation rate can be independent of the plasma resistivity if the merging is suitably driven. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872754
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  • 4
    Electronic Resource
    Electronic Resource
    Exact solutions for steady-state, planar, magnetic reconnection in an incompressible viscous plasma (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2243-2247 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The exact planar reconnection analysis of Craig and Henton [Astrophys. J. 450, 280 (1995)] is extended to include the finite viscosity of the fluid and the presence of nonplanar components in the magnetic and velocity fields. It is shown that fast reconnection can be achieved for sufficiently small values of the kinematic viscosity. In particular, the dissipation rate is sustained by the strong amplification of planar magnetic field components advected toward the neutral point. By contrast, nonplanar field components are advected without amplification and so dissipate energy at the slow Sweet–Parker rate. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871932
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  • 5
    Electronic Resource
    Electronic Resource
    Fast magnetic reconnection and the coalescence instability (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 956-964 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic reconnection that occurs during the nonlinear development of the coalescence instability is considered. The structure of the reconnection region at the time of maximum current as a function of the resistivity η is analyzed in detail using a compressible magnetohydrodynamic fluid code. It is shown that the numerical results concur remarkably well with a simple scaling analysis which predicts the dependence of the reconnection region structure on η. It is argued that the flow topology is crucial in maintaining the "fast'' reconnection rate. The results indicate a flux pileup solution in which the flux annihilation rate is approximately independent of η, whereas the Ohmic dissipation rate scales as η−1/3. The possibility that these scalings break down at lower values of η is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860945
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  • 6
    Electronic Resource
    Electronic Resource
    Are coronal loops stable? (1981)
    [s.l.] : Nature Publishing Group
    Nature 294 (1981), S. 333-334 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The central assumption in theoretical loop modelling is that dynamic effects can be neglected in the local energy balance6. Hence it is postulated that an unknown heating mechanism supports the loop against energy losses by radiation and energy redistribution by heat conduction along the confining ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/294333a0
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  • 7
    Electronic Resource
    Electronic Resource
    Why measure astrophysical X-ray spectra? (reply) (1977)
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 411-412 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Simplicity of models'?-Gabriel's point of smoothness in £〉(T) is well taken but a half sine wave in (1-10) x 106 K fits the data and is simpler (one Fourier term less) than his "unique simplest solution" without remotely resembling it. It is also positive everywhere, which may please our ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/267411a0
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  • 8
    Electronic Resource
    Electronic Resource
    Why measure astrophysical X-ray spectra? (1976)
    [s.l.] : Nature Publishing Group
    Nature 264 (1976), S. 340-342 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In addition to providing useful data through measurements of Doppler shifts and line profiles, a prime aim of high resolution spectrometry is the inference of source structure in terms of temperature distribution of thermal particles3?6 or energy distribution of non-thermal particles6. These ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/264340b0
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  • 9
    Electronic Resource
    Electronic Resource
    Solution of the electron continuity equation in an inhomogeneous medium via the method of characteristics (1985)
    Springer
    Astrophysics and space science 116 (1985), S. 377-387 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Many astrophysical problems require a knowledge of the spatial and temporal evolution of fast electron distributions as they interact (e.g., collisionally) with an ambient medium; an example is provided by hard X-ray burst modelling in solar flares. In the mean scattering-rate approximation (which neglects dispersion in the distribution function), this evolution is governed by the continuity equation in phase space. Here we present a rigorous solution of the continuity equation, derived via the method of characteristics, which confirms and generalises the results of previous authors, and gives greater physical and mathematical insight into these solutions. We illustrate the calculation of this solution for mildly relativistic electrons undergoing Coulomb collisions, and briefly indicate the extension of the method to other physical situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653792
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  • 10
    Electronic Resource
    Electronic Resource
    Inference of relativistic electron spectra from measurements of inverse compton radiation (1980)
    Springer
    Astrophysics and space science 70 (1980), S. 425-432 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The inference of relativistic electron spectra from spectral measurement of inverse Compton radiation is discussed for the case where the background photon spectrum is a Planck function. The problem is formulated in terms of an integral transform that relates the measured spectrum to the unknown electron distribution. A general inversion formula is used to provide a quantitative assessment of the information content of the spectral data. It is shown that the observations must generally be augmented by additional information if anything other than a rudimentary two or three parameter model of the source function is to be derived. It is also pointed out that since a similar equation governs the continuum spectra emitted by a distribution of black-body radiators, the analysis is relevant to the problem of stellar population synthesis from galactic spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00639566
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