ENERGETIC ATOMIC AND MOLECULAR-IONS OF IONOSPHERIC ORIGIN OBSERVED IN DISTANT MAGNETOTAIL FLOW-REVERSAL EVENTS

Energetic atomic (O+1 and N+1) and molecular (O-2(+1), NO+1, and N-2(+1)) ions of ionospheric origin were observed in Earth's magnetotail at X similar to -146 R(E) during two plasma sheet sunward/tailward now-reversal events measured by instruments on the GEOTAIL spacecraft. These events were associated with concurrent ground-measured geomagnetic disturbance intensification at auroral- and mid-latitudes (Kp = 7(-)). Energetic ions in the sunward-component and tailward flows were from both the solar wind and ionosphere. Plasma and energetic ions participated in the flows. During tailward flow, ionospheric origin ion abundance ratios at similar to 200-900 km/s in the rest frame were N+1/O+1 = similar to 25-30% and (O-2(+1), NO+1, and N-2(+1))/O+1 = similar to 1-2%. We argue that tailward flow most likely initiated similar to 80-100 R(E) tailward of Earth and molecular ions were in the plasma sheet prior to geomagnetic intensification onset.