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Fast magnetic reconnection in extragalactic jets leads to electron acceleration by the DC electric field in the reconnecting current sheet. The maximum electron energy (γ > 106) and the acceleration time (< 106 s) are determined by the magnetic field dynamics in the sheet.
On the basis of the Yohkoh data on the site and mechanism of magnetic energy transformation into thermal and kinetic energies of superhot plasmas and accelerated particles, a model is developed that explains observed properties of collisionless 3D reconnection in active regions. The model makes intelligible the observed relation between the S-like morphology and eruptive activity.
Radio astronomy has seen major advances in both instrumentation and scientific discovery during the last three years. This report is not encyclopedic but is intended to show the breadth of activity in the field. Division X is a technique-based division, and radio telescopes are becoming increasingly more international in character and usage. For these reasons this report devotes considerable attention to advances in instrumentation. More complete information on radio telescopes and scientific advances in the field can be found at the following Web site: http://www.stsci.edu/science/net-resources.html
An exact self-similar solution is used to investigate current sheet formation at a magnetic neutral line in incompressible Hall magnetohydrodynamics. The collapse to a current sheet is modelled as a finite-time singularity in the solution for electric current density at the neutral line. We establish that a finite-time collapse to the current sheet can occur in Hall magnetohydrodynamics, and we find a criterion for the finite-time singularity in terms of the initial conditions. We derive an asymptotic solution for the singularity formation and a formula for the singularity formation time. The analytical results are illustrated by numerical solutions, and we also investigate an alternative similarity reduction. Finally, we generalise our solution to incorporate resistive, viscous and electron inertia terms.