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Nonlinear wave propagation and reconnection at an X-point in Hall MHD

Author: James Threlfall

University of St Andrews

Co-Authors: I.De Moortel (University of St Andrews), C.E.Parnell (University of St Andrews), K.G.McClements (EURATOM/CCFE), T.D.Arber (University of Warwick).

Session: MST1: Magnetic Reconnection in Space and Astrophysical Plasmas

Presentation type: Talk      10:41  Thursday 29th 10:00-11:15 


We investigate the role of the Hall term in the propagation and dissipation of waves which interact with 2D magnetic X-points, in order to determine how the evolution of a nonlinear fast magnetoacoustic wave pulse, and the oscillatory reconnection which results from its interaction with a line-tied 2D magnetic X-point, is affected by the inclusion of the Hall term in the generalised Ohm's law. A Lagrangian remap shock-capturing code (Lare2d) is used to study the evolution of an initial fast magnetoacoustic wave annulus for a range of values of ion skin depth (di) in resistive Hall MHD. In general, the fast wave is coupled to a shear wave and to whistler and ion cyclotron waves. Dispersive whistler effects cause rapid oscillations of the X-point, leading to the creation of magnetic islands and multiple null points under the influence of the Hall term. At later times, competition of local Lorentz and gas pressure forces return the system to a near-equilibrium state. The rate of oscillatory reconnection recovered during this relaxation phase appears to be unaffected by the value of di. This work was partly funded by the RCUK Energy Programme under grant EP/I501045 and the European Communities under the contract of Association between EURATOM and CCFE. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

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