Multiscale coherent structures and broadband waves due to parallel inhomogeneous flows

Linear theory analysis and particle-in-cell simulations show that a spatial transverse gradient in the ion drift parallel to the magnetic field, dV(di)/dx less than or equal to Omega (i), where Omega (i) is the ion cyclotron frequency, can generate a broadband multimode spectrum extending from omega much less than Omega (i) to omega much greater than Omega (i). Nonlinearly, these waves lead to multiscale spatially coherent structures, substantial cross-field transport, ion energization, and phase-space diffusion. Large spikes are formed in the parallel electric field time series. These signatures are similar to the Fast Auroral Snapshot satellite observations in the upward current region.