Diverse plasma populations and structures in Jupiter's magnetotail

Jupiter's magnetotail is the largest cohesive structure in the solar system and marks the loss of vast numbers of heavy ions from the Jupiter system. The New Horizons spacecraft traversed the magnetotail to distances exceeding 2500 jovian radii (R_J) and revealed a remarkable diversity of plasma populations and structures throughout its length. Ions evolve from a hot plasma disk distribution at ∼100 R_J to slower, persistent flows down the tail that become increasingly variable in flux and mean energy. The plasma is highly structured - exhibiting sharp breaks, smooth variations, and apparent plasmoids - and contains ions from both Io and Jupiter's ionosphere with intense bursts of H⁺ and H₃⁺. Quasi-periodic changes were seen in flux at ∼450 and ∼1500 R_J with a 10-hour period. Other variations in flow speed at ∼600 to 1000 R_J with a 3- to 4-day period may be attributable to plasmoids moving down the tail.