On artificial geomagnetic and ionospheric storms associated with high-altitude explosions

Abstract

Geophysical effects of nuclear explosions at Johnston Island on August 1 and 12, 1958, were studied by means of IGY geomagnetic and ionospheric data collected at various stations in the Pacific area and the American continent. The explosion heights are estimated at 70 to 80 km and about 40 km, respectively. Immediately after each explosion, three phenomena occurred. (1) Strong counterclockwise circular electric currents were formed in the vicinty of Johnston Island at 80- to 100-km height. They caused the immediate occurrence of artificial magnetic storms in the central Pacific. (2) High-energy particles moving along the magnetic lines of force caused auroras seen from Apia, and also caused the main parts of the magnetic storms observed at Apia. (3) X-rays due to the explosion caused the increase of the D-region absorption observed at Maui. Irregularities of the electron density in the F-layer at Maui and the maximum geomagnetic change at Honolulu were caused by a shock wave from the explosion. The degree of ionization in a wide area in the central Pacific increased to about 10 times normal within 35 min after the first explosion and within about 6 hr after the second. Then a strong radio absorption continued for many hours.