Juno Observations of Ion-Inertial Scale Flux Ropes in the Jovian Magnetotail

Two ion-inertial scale magnetic flux ropes are identified in the Juno magnetic field measurements in the dawnside Jovian magnetotail. Previously reported plasmoids in this region had typical diameters of several Jovian radii (R_J). However, events reported here are only ∼0.15–0.19 R_J in diameter, assuming that they move at the local Alfven speed. Using the plasma density determined by the Juno Waves instrument, the diameters are calculated to be on the order of the local ion inertial length (∼0.6–1.6 d_i). Multiple reversals in the north-south component are observed ∼30 min before one of these events, which suggests that plasmoid ejection in the dawnside magnetotail may proceed via multiple X-line reconnection in a highly thinned cross-tail current sheet in a manner similar to that observed at Mercury and Earth. Further studies will be required to determine the contribution of these small flux ropes to mass loss through plasmoid ejection.