Abstract
The generation of dc magnetic fields in unmagnetized electron-ion shear flows is shown to be associated to either initial thermal effects or the onset of electron-scale shear instabilities, in particular the cold Kelvin-Helmholtz instability. This mechanism, intrinsic to shear gradients on the electron scale, is described through a kinetic model that predicts the growth and the saturation of the dc field in both scenarios. The theoretical results are confirmed by multidimensional particle-in-cell simulations, demonstrating the formation of long-lived magnetic fields () along the full longitudinal extent of the shear layer, with a typical transverse width of , reaching magnitudes for an initial sharp shear. The case of an initial smooth shear is also discussed.
- Received 30 October 2012
DOI:https://doi.org/10.1103/PhysRevLett.111.015005
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