Kelvin-Helmholtz Unstable Magnetotail Flow Channels: Deceleration and Radiation of MHD Waves

The Kelvin-Helmholtz instability (KHI) of magnetotail flow channels associated with burstybulk flows (BBFs) is investigated. MHD oscillations of the channel in both kink and sausage modes areinvestigated for KHI, and both the primary and secondary KHIs are found that drive MHD waves. Theseinstabilities are likely to be important for flow channel braking where the KHI removes energy from the flow.At flow speeds above the peak growth rate, the MHD modes excited by KHI develop from surface modesinto propagating modes leading to the radiation of MHD waves from the flow channel. The coupling ofBBF-driven shear flow instabilities to MHD waves presented here represents a new paradigm to explain BBFexcitation of tail flapping. Our model can also explain, for the first time, the generation mechanism for theobservations of waves propagating toward both flanks and emitted from BBF channels in the magnetotail.