Ion-density measurements in the stratosphere

Abstract

The number density of small negative ions in the atmosphere was measured in 1958 on a series of eight balloon flights which reached altitudes of 115,000 feet over Minneapolis (45°N). A pronounced decrease in the number density of small negative ions was observed at the tropopause on seven of the eight flights, and similar decreases were observed at numerous temperature inversions in the stratosphere. The results strongly suggest the presence and bunching of ‘dust’ above the temperature inversions. In the absence of dust and ionizing agents other than cosmic rays, the number density of negative ions increases with altitude to 50,000 feet, where a maximum of approximately 5500 ions/cm3 occurs. Above this altitude the number density decreases to a value near 2000 ions/cm3 at 115,000 feet; this result is contrary to the almost constant value expected in the stratosphere from cosmic-ray data and the Thomson theory.