Pressure anisotropy and small spatial scales induced by velocity shear.
By including the full pressure tensor dynamics in a fluid plasma model, we show that a sheared velocity field can provide an effective mechanism that makes the initial isotropic pressure nongyrotropic. This is distinct from the usual gyrotropic anisotropy related to the fluid compressibility and usually accounted for in double-adiabatic models. We determine the time evolution of the pressure agyrotropy and discuss how the propagation of "magnetoelastic perturbations" can affect the pressure tensor anisotropization and its spatial filamentation, which are due to the action of both the magnetic field and the flow strain tensor. We support this analysis with a numerical integration of the nonlinear equations describing the pressure tensor evolution.
Institut Jean Lamour, UMR CNRS 7198 and Université de Lorraine, B.P. 70239, F-54506 Vandœuvre-lès-Nancy Cedex, France.
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Del Sarto
Physics Department and CNISM, University of Pisa, 56216 Pisa, Italy.
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Pegoraro
Physics Department and CNISM, University of Pisa, 56216 Pisa, Italy.
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Califano