“dc-Magnetic-Field Generation in Unmagnetized Shear Flows” by Thomas Grismayer et al. was published in Physical Review Letters. It describes the mechanism, intrisic to shear gradients on the electron scale, of the generation of dc magnetic fields. The 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. More information can be founded here.

Fig. 1 – B_z component of the magnetic-field structure generated by the cold KHI for v₀=0.2c during (a) the linear regime, (b) near saturation, and (c) at w_pe*t =1000. The insets on the right hand side represent the longitudinal average of the magnetic field, revealing the dc component.