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Why did a high-altitude U.S. nuclear test affect electrical equipment in Hawaii in 1962?

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U.S. hydrogen bomb test in the Marshall Islands — nuclear weapon A test of a U.S. thermonuclear weapon (hydrogen bomb) at Enewetak atoll in the Marshall Islands, November 1, 1952.

The electrical disturbances in Hawaii during the 1962 high-altitude nuclear test at Johnston Atoll were caused by a nuclear electromagnetic pulse (EMP).21

When a nuclear device detonates at high altitude, it releases intense gamma radiation. These rays collide with air molecules, triggering the Compton effect, which ejects high-energy electrons. This process separates positive and negative charges in the atmosphere, creating a massive electric field. Asymmetries in this field—influenced by factors like air density—generate time-varying electrical currents that produce the EMP.21

These pulses can induce damaging currents and voltages in electronic equipment located hundreds or even thousands of kilometers away. In the 1962 incident, this phenomenon caused electronic components in Hawaiian street lights to fail and triggered numerous automobile burglar alarms in Honolulu, despite the test site being approximately 1,300 km (800 miles) away. To protect critical infrastructure from such effects, engineers utilize a process known as "hardening" to improve the resilience of electronic systems.21