2008 (IPP)

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    MHD modes of solar wind flow tubes
    (2008-02) Chandra, Suresh
    Nakariakov & Roberts (1995) and Nakariakov et al. (1996) investigated the linear mag- netosonic waves trapped within solar wind ow tubes by accounting for a slab having boundaries at x = d and extended up to in nity in y and z directions. They obtained dispersion relations for sausage and kink surface waves in incompressible plasma. Following the approach of Nakariakov & Roberts (1995), we have obtained dispersion relations for sausage and kink surface waves in a compressible plasma. Values of the parameter a !=kCAo are found to vary in the ranges 0.755 0.849 and 1.080 1.356 for the sausage waves and in the ranges 0.850 0.882 and 1.358 1.538 for the kink waves in the compressible plasma. It shows an interesting feature that the sausage and kink surface waves are exclusive from each other.
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    Kinematic alpha effect in isotropic turbulence simulations
    (2008-01) Sur, Sharanya; Brandenburg, Axel; Subramanian, Kandaswamy
    Using numerical simulations at moderate magnetic Reynolds numbers up to 220 it is shown that in the kinematic regime, isotropic helical turbulence leads to an alpha effect and a turbulent diffusivitywhose values are independent of the magnetic Reynolds number,Rm, provided Rm exceeds unity. These turbulent coefficients are also consistent with expectations from the first order smoothing approximation. For small values of Rm, alpha and turbulent diffusivity are proportional to Rm. Over finite time intervals meaningful values of alpha and turbulent diffusivity can be obtained even when there is small-scale dynamo action that produces strong magnetic fluctuations. This suggests that small-scale dynamo-generated fields do not make a correlated contribution to the mean electromotive force.