Fall-day auroral-zone atmospheric structure measurements from 100 to 188 km

Abstract

The density and pressure of the atmosphere from 100 to 188 km above Fort Churchill, Manitoba, Canada, were determined from the IGY NN 3.15 Aerobee-Hi rocket flight on October 31, 1958, at 2:00 P.M., CST. Two magnetic cold-cathode ionization gages were used to measure pressure and pressure changes on the side of the rolling rocket. Excellent agreement was obtained (a) between the two gages throughout flight, and (b) between ascent and descent measurements. Measured pressures in the region from 100 to 112.5 km were corrected for a residual gas pressure of approximately 3×10−5 mm Hg. An ambient pressure of 10−4 mm Hg was obtained at 106 km. The derived pressure of 2.3×10−6 mm Hg at 188 km is approximately a factor of 2 lower than the corresponding arctic summer-day value. Densities were measured from 130 to 188 km. The density value of 5.2×10−7 g/m3 at 188 km is approximately 40 per cent lower than the summer-day value. The density profile presented here is in good agreement with the arctic November-day density point obtained at 200 km in 1956. Scale heights (RT/Mg) were derived from the measured pressure and density data vs. altitude, using the hydrostatic equation. The scale height value obtained at 188 km was 63 km, and the scale height gradient from 180 to 188 km was 0.5 km/km.