A suggestion that two‐dimensional turbulence contributes to polar cap convection for B_z north

Abstract

[1] Recently, a linear dependence has been found between the polar cap potential and the log of ULF power in the solar wind for B z north. We argue here that this is very strong evidence that Alfvén waves propagating from the solar wind to the polar cap drive two-dimensional turbulence in agreement with other work along these lines. In brief, two-dimensional (2-D) turbulence is characterized by an inverse cascade of energy from intermediate to large scales, eventually leading to two large counter-rotating vortices filling the available volume and, we think, creating two of the four vortices in the B z north polar cap. In this model, the Alfvén waves create velocity shear at the 500 or so kilometer scale associated with polar cap arcs. This energy/vorticity then inverse cascades to fill the polar cap.Citation: Kelley, M. C., and H.-J. Kim (2012), A suggestion that two-dimensional turbulence contributes to polar cap convection for B z north, Geophys. Res. Lett., 39, L07102,