Positive ion composition and derived particle heating in the lower auroral ionosphere

Two E11a rocket flights in salvo B (launched on November 16, 1980) and A2 (launched on November 30, 1980), which provide positive ion composition, total and partial ion density, and electron density in the altitude range 60-170 km above Kiruna under conditions of moderate and strong magnetic disturbance, are examined. It is shown that the ionization sources are predominantly precipitating electrons in salvo B and precipitating protons in salvo A2. Under winter-time auroral conditions the characteristics of the positive ion composition are large NO(+)/O2(+) density ratios, with maximum values of 20 at 118 km in salvo B and 100 at 100 km in salvo A2, respectively. The transition from NO(+) to proton hydrates is found at an altitude of 79 km in salvo B and 76 km in salvo A2. The calculated O(+) and N(+) densities are in good agreement with model calculations and from these calculations it is concluded that 28(+) is mainly N2(+) above 110 km in salvo B and above 105 km in salvo A2, and Si(+) below these altitudes. By altitude integration of the ion-electron pair production, the energy flux of precipitating particles is found to have values of 0.85 mW/sq m and 1.0 mW/sq m in salvoes B and A2, respectively.