Observations of molecular ions in the Earth's magnetosphere

Abstract

The retarding ion mass spectrometer on Dynamics Explorer 1 operating over the polar cap during a large magnetic storm has measured fluxes of up to 106 ions cm−2 s−1 of the molecular ions N2+, NO+, and O2+. These ions were measured beginning low in the satellite orbit (1.1 RE) and extending to about 3 RE geocentric altitude. Near perigee, the ions have a rammed distribution indicating a cold Maxwellian plasma (1000°–2000°K). The molecular ions gradually shift to a field‐aligned distribution at the higher altitudes. An upward flow of 5–10 km/s is found in these field‐aligned measurements. The density of the molecular ions is on the order of 2 cm−3 at all altitudes, and the energy of the ions generally increases as the satellite moves sunward across the southern polar cap. Kinetic energies of at least 20 eV were found at 2.5 RE geocentric distance.