A determination ofFregion effective recombination coefficients from the Echo 2 Sounding Rocket Plasma Wave and Particle Measurements

The effective dissociative recombination coefficient is calculated at 140- and 225-km altitude by using the Echo 2 rocket flight data. The density of ambient electrons in the immediate vicinity of the rocket payload was measured by the detection of plasma frequency emissions produced by the injection of 40-keV electrons from the accelerator carried aboard the rocket. Electrostatic analyzers measured the directional intensity of the weak auroral precipitation producing the ionization. Under the assumption of equilibrium conditions the value of α obtained at 140 km was between 1.3 × 10−7 and 1.7 × 10−7 cm³ s−1, depending on the pitch angle distribution of the precipitated auroral electrons used in the calculation of the ion production rate. The recombination coefficient obtained at 225 km varied from 1.2 to 6.2 × 10−9 cm³ s−1. The 140-km values compare favorably with laboratory data and are consistent with previous satellite and rocket measurements. The 225-km values are much less certain in that the data suggest that transport of ionization cannot be ignored at this altitude. Both the 140-km and the 225-km values could be low, due to lack of knowledge of the local spectrum below 0.9 keV.