Cosmic-ray ionization in the lower atmosphere

Abstract

The response of a pressurized argon‐filled ionization chamber to charged particles in the cosmic radiation near 50°N geomagnetic latitude has been determined as a function of atmospheric depth from mountain altitudes to sea level. The γ contributions to the various ionization chamber readings were subtracted out by utilizing concurrent determinations of the γ ionization from γ‐ray energy spectra obtained with a scintillation spectrometer. Conversion of relative response to absolute free air ionization is accomplished by normalizing the mean chamber reading at sea level to a calculated value of 2.1±0.1 ion pairs cm−3/sec−1 atm−1 (STP), derived from existing experimental data on muon, electron, and proton fluxes and energy distributions. The curve of absolute ionization versus atmospheric depth has the same shape as that obtained by Millikan in 1932, but with significantly lower absolute values. It is inferred that many present determinations of free‐air ionization, primarily conducted at higher altitudes, may be as much as 50% too high.

Calibration Factors for Ge Detectors Used for Field Spectrometry

“…To make this comparison, we present for the reader's convenience in Fig. 6 the cosmic-ray secondaryexposure-rate equivalent and dose rate in air as a function of altitude and barometric pressure for mid-latitudes as derived from Lowder and Beck (1966). In a strict sense, the quantity "exposure rate" is only applied to y rays of certain energies.…”

A survey of possible effects of long-lasting absence of solar activity on climate and some speculations on possible mechanisms

“…On the other hand the galactic cosmic rays ionize the tropospheric molecules too (see e.g. Lowder and Beck, 1966), so their solar activity-dependent modulation may eventually lead to electrical changes. At the level of our present knowledge these changes might not induce significant weather effects, although e.g.…”

Hazards Control Progress Report No. 40, May--August 1971.

“…Preliminary indications are that this dosimeter ovenesponds by only a factor of 2 with heavy hydrogenous moderators when compared to a bare 2 ' 2 Cf spectrum calibration, and (hat it should be able to detect a neutron dose of 30 mrem in the presence of a 100 mR gamma exposure.…”

“…We calibrated each of the remeters at 50 mrem from an unmoderated " 2 Cf source in a 30-cm diameter DjO sphere, and in a 50-cm diamecer D 2 0 sphere. The calibrations were made by comparison with an active remeter connected to a scaler.…”