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  • 1
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871932
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872121
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872569
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872754
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  • 5
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860945
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  • 6
    Digitale Medien
    Digitale Medien
    An explanation for fast downflows on the Sun (1986)
    [s.l.] : Nature Publishing Group
    Nature 324 (1986), S. 128-129 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Observed flows exhibit several features that must be explained by any convincing theory. First, the flows are observed to persist much longer than the transit time of a gas element through the loop10'11. This fact alone suggests a quasi-steady model in which plasma flows continually from one ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/324128a0
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  • 7
    Digitale Medien
    Digitale Medien
    Are coronal loops stable? (1981)
    [s.l.] : Nature Publishing Group
    Nature 294 (1981), S. 333-334 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [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 ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/294333a0
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  • 8
    Digitale Medien
    Digitale Medien
    Why measure astrophysical X-ray spectra? (1976)
    [s.l.] : Nature Publishing Group
    Nature 264 (1976), S. 340-342 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [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 ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/264340b0
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  • 9
    Digitale Medien
    Digitale Medien
    Why measure astrophysical X-ray spectra? (reply) (1977)
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 411-412 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [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 ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/267411a0
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  • 10
    Digitale Medien
    Digitale Medien
    The kink instability in infinite cylindrical flux tubes: Eigenvalues for power-law twist profiles (1990)
    Springer
    Astrophysics and space science 166 (1990), S. 289-300 
    Details
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We develop simple accurate methods of calculating ideal MHD instability eigenvalues λ for infinitely-long cylindrical tubes, with twist functionT(r)=B θ/rB z . A complete theoretical treatment is presented for force-free magnetic equilibria with arbitraryT(r), and detailed semi-analytic results for the kink instability are given for the particular case of a power-law twistT(r)=r ν, where the index ν is non-negative. Our results show that the most rapidly growing and energetic instabilities occur in the Gold-Hoyle ν=0 field, with the instability progressively weakening with increasing ν. However, the maximum force eigenvalue is always small, so that even in the Gold-Hoyle case (where λ=O(10−2) in dimensionless units) only a small proportion of the available magnetic energy can be released in the linear phase. Our results also confirm that the linear pinch (ν=∞) is remarkably weak (λ=O(10−3)) yet relatively resistant to line-tying! It is shown that the weakness of the force eigenvalue implies that the influence of uniform gas pressure on stability is negligible. Implications for the energy-release mechanism in solar flares are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01094900
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