Hydromagnetic waves generated by the July 9, 1962, nuclear weapons test as observed at College, Alaska

Abstract

Magnetic effects of the July 9, 1962, high-altitude nuclear weapons test near Johnston Island are studied by means of the record obtained with a rubidium vapor magnetometer at College, Alaska, and the records taken by the U. S. Coast and Geodetic Survey at College and Sitka, Alaska. The first event recorded by the rubidium magnetometer was a sudden increase in the total field 2.1 sec after the detonation; this was followed by a large-amplitude oscillation of period 2.5 to 3 sec, which drove the recorder off scale for several cycles. The first impulse is interpreted as a predominantly longitudinal hydromagnetic wave generated by the detonation. The second event, which commenced 52 sec after the detonation, was recorded by the rubidium magnetometer as a 3 γ negative impulse lasting about 8 sec. The third phase of the bomb effect was a large-amplitude magnetic perturbation of much longer period than the first event, beginning 66 sec after the detonation. This event is interpreted as the arrival of a transverse hydromagnetic wave generated in the magnetosphere at several earth radii and transmitted along the lines of magnetic force to the earth; the transverse wave was generated in the magnetosphere by coupling with the compressional hydromagnetic wave that propagated outward near the equatorial plane from the detonation point.