Generation of runaway electrons by atmospheric radionuclides in a thunderstorm electric field

Torii, Tatsuo  ; Sugita, Takeshi*

The influence of runaway electron generation by atmospheric radionuclides in a thunderstorm electric field is examined. The behavior of radiation emitted by radon, thoron and their decay products in the electric field was analyzed by Monte Carlo calculations. The results showed that a large amount of electron-ion pairs are produced in air when the electric field intensity exceeds 250 kV/m at the altitude of 2 km (about 320 kV/m at the sea-level equivalent pressure). Furthermore, the influence of the resuspension of fallout nuclides was analyzed because lightning activity after the Chernobyl nuclear accident increased in central Sweden where a considerable amount of nuclides fell. It is shown that, similar to natural radioactive nuclides, these nuclides significantly influence the ionization within the thundercloud.