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, dVdi/dx≤Ωᵢ, where Ωᵢ is the ion cyclotron frequency, can generate a broadband multimode spectrum extending from ωΩᵢ to ωΩᵢ. 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.