Multiple Auroral Streamer Bundles in Conjugate Hemispheres and Multiple Near-Earth Injections

The auroral streamer is a type of auroral form commonly observed during geomagnetic substorms. Previous studies suggested a coupling between auroral streamers and channels of bursty bulk flows in the plasma sheet. However, whether one flow channel can map to multiple streamers is unclear. Here, we present an event containing consecutive auroral streamer subevents. The event features similar spatial and temporal development of auroral streamers in conjugate hemispheres. In most of the subevents, we observed that what an in-space auroral camera saw as one streamer actually consisted of multiple streamers (i.e., a streamer bundle). A coordinated analysis of near-earth injections and ionospheric currents suggests that one overall flow channel (or bubble) can map to a streamer bundle. Multiple streamer bundles and thus multiple overall flow channels can occur simultaneously at different local times. Evidence supports that the overall flow channel may consist of or split into several narrower flow channels and each maps to a streamer and causes a particle injection. Plain Language Summary Geomagnetic substorm is a complex energy release process involving many observable features in the geospace. Common substorm features include enhanced auroral activities and currents in the ionosphere, enhanced fluxes of energetic electrons and ions (injections), and localized bursty bulk flows (BBFs) in the nightside magnetosphere. It is well established that injection, BBF, and a type of aurora called auroral streamer are physically related. Here, we present an event when streamers form bundles in successive subevents and discuss how streamers and streamer bundles are related to BBF and injection. Auroral data show that these streamer bundles developed similarly in both hemispheres. We show observational evidence that a streamer bundle maps to an overall BBF and streamers within a bundle map to narrower BBFs.