Abstract
The results of measurement of positive ions to an altitude of 520 km with two spherical electrostatic analyzers mounted on a Thor rocket launched at 1300 hours local time are presented. The experimental results obtained below the F2 peak agree to within 20 per cent with simultaneous ionosonde data. Assuming that thermodynamic equilibrium exists above the F2 peak, the ion scale height is calculated to be 155±10 km and the ion temperature is found equal to 1300±50°K. A theoretical charge distribution was calculated assuming electrons to be produced by photoionization and destroyed by dissociative recombination of NO+, N2+, O2+, and by radiative recombination. Recent experimentally determined values of ion composition, photoionization rates, and dissociative recombination coefficients were used in solving the continuity equation. Excellent agreement is found between the experimental and theoretical charge distributions in the region 150 to 520 km. The altitude of maximum density was measured to be 315 km, the theoretical calculation gives 320 km; the magnitudes differ by a constant factor of 1.4 to 2.0, depending on the values chosen for the dissociative recombination coefficients. Dissociative recombination is found to be the principal electron loss mechanism to 520 km. The theory of measurement of positive ions by means of two-electrode spherical electrostatic analyzer is derived for the case of a Maxwellian gas where (a) the vehicle velocity is variable with respect to the most probable ion velocity, and (b) the mean free path is large compared to the dimensions of the analyzer.
Published Version
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