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  • Copernicus  (5)
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Erscheinungszeitraum
  • 1
    Publikationsdatum: 2011-01-13
    Beschreibung: As a sequence of Ugai (2010b), the present paper studies in detail the structure and dynamics of large-scale (principal) plasmoid, generated by the fast reconnection evolution in a sheared current sheet with no initial northward field component. The overall plasmoid domain is divided into the plasmoid reconnection region P and the plasmoid core region C. In the region P, the magnetized plasma with reconnected field lines are accumulated, whereas in the region C, the plasma, which was intially embedded in the current sheet and has been ejected away by the reconnection jet, is compressed and accumulated. In the presence of the sheared magnetic field in the east-west direction in the current sheet, the upper and lower parts of the reconnection region P are inversely shifted in the east-west directions. Accordingly, the plasmoid core region C with the accumulated sheared field lines is bent in the north-south direction just ahead of the plasmoid center x=XC, causing the magnetic field component in the north-south direction, whose sign is always opposite to that of the reconnected field lines. Therefore, independently of the sign of the initial sheared field, the magnetic field component Bz in the north-south direction has the definite bipolar profile around XC along the x-axis. At x=XC, the sheared field component has the peak value, and as the sheared fields accumulated in the region C become larger, the bipolar field profile becomes more distinct.
    Print ISSN: 0992-7689
    Digitale ISSN: 1432-0576
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Publikationsdatum: 2009-06-08
    Beschreibung: Three-dimensional configuration of earthward fast flow in the near-Earth plasma sheet is studied using three-dimensional magnetohydrodynamics (MHD) simulations on the basis of the spontaneous fast reconnection model. In this study, the sheared magnetic field in the plasma sheet is newly considered in order to investigate the effects of it to the earthward fast flow, and the results are discussed in comparison with no-shear simulations. The virtual probes located at different positions in our simulation domain in shear/no-shear cases could explain different behavior of fast flows in the real observations.
    Print ISSN: 0992-7689
    Digitale ISSN: 1432-0576
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Publikationsdatum: 2010-08-11
    Beschreibung: On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x=XC, where the north-south field component changes its sign. The plasmoid center corresponds to the so-called contact discontinuity that bounds the reconnected field lines in xXC. Hence, contray to the conventional prediction, the reconnected sheared field lines in xXC. It is demonstrated that the resulting profiles of magnetic field components inside the plasmoid are, in principle, consistent with satellite observations. In the ambient magnetic field region outside the plasmoid too, the magnetic field profiles are in good agreement with the well-known observations of traveling compression regions (TCRs).
    Print ISSN: 0992-7689
    Digitale ISSN: 1432-0576
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Publikationsdatum: 2008-12-02
    Beschreibung: The fast reconnection mechanism, involving slow shocks and Alfvénic fast plasma jets, is most responsible for the explosive conversion of magnetic energy associated with geomagnetic substorms and solar flares. In this paper, the spontaneous fast reconnection model is applied to well-known phenomena of substorms. When the east-west width of the tail current sheet becomes 3–4 times larger than its north-south thickness, the fast reconnection mechanism can fully be established, which may lead to substorm onset. The resulting Alfvénic jet can exactly explain, both qualitatively and quantitatively, the in-situ satellite observations of the traveling compression regions (TCRs) associated with large-scale plasmoids propagating down the tail. Also, the earthward fast reconnection jet causes drastic magnetic field dipolarization, so that the sheet current ahead of the magnetic loop of closed field lines suddenly turns its direction toward the loop footpoint and a large-scale current wedge is formed according to the growth of field-aligned currents. It is demonstrated that an MHD generator arises ahead of the magnetic loop and drives the current wedge to distinctly enhance the current density in a pair of thin layers of the loop footpoint, giving rise to drastic heating in the form of two ribbons.
    Print ISSN: 0992-7689
    Digitale ISSN: 1432-0576
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Publikationsdatum: 2011-08-23
    Beschreibung: The present paper studies fundamental features of plasmoid propagation by virtual satellite observations in the simulation box. The plasmoid domain is divided into the plasmoid reconnection region P, where magnetized plasmas with reconnected field lines, heated by dissipation mechanisms of fast reconnection, are accumulated, and the plasmoid core region C, where magnetized plasmas with sheared field lines, initially embedded in the current sheet, is adiabatically compressed. When the virtual satellite is located in a position through which the plasmoid core region passes, it detects distinct changes in quantities at the interface between the regions P and C, where the north-south field component Bz has the bipolar profile and the sheared field component By has the peak value. The observed magnetic field profile is, both quantitatively and qualitatively, in good agreement with the standard one detected by actual satellite observations, although when the satellite location is very close to the X neutral line, where reconnection occurs, the Bz field profile becomes dipolarization-like rather than bipolar. If the satellite detects only the plasmoid region P outside region C, the standard magnetic field profile becomes obscure even if notable plasmoid signatures, such as enhanced plasma temperature and plasma flow, are observed. Unlike the traditional flux rope model based on multiple reconnections, it is demonstrated that the standard magnetic field profile, observed for plasmoids propagating in the geomagnetic tail, is the direct outcome of the single fast reconnection evolution.
    Print ISSN: 0992-7689
    Digitale ISSN: 1432-0576
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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