For centuries, people in high-latitude regions have reported hearing sounds accompanying the Northern Lights. While these anecdotal accounts were often dismissed as folklore, modern scientific inquiry suggests a more complex reality. Research is revealing the conditions under which these elusive sounds might genuinely occur.
Historical Accounts and Anecdotes
Across diverse cultures, anecdotal reports describe sounds associated with the Northern Lights. Witnesses recounted hearing crackling, hissing, swishing, popping, or muffled banging noises during intense displays. Indigenous communities, such as the Inuit and Sami, incorporated these sounds into their oral traditions. For example, some Inuit folklore described the sounds as spirits, while the Sami spoke of a “klip-klap” sound.
These historical accounts were often met with skepticism by the scientific community. The aurora’s high altitude led many to believe any perceived sounds were likely psychological phenomena or auditory illusions, rather than a direct physical manifestation.
The Science Behind Auroral Sounds
The aurora occurs at high altitudes, typically 80 to 100 kilometers above Earth’s surface. It forms when charged particles from the sun’s solar wind collide with atmospheric atoms, causing them to emit light.
Due to the atmosphere’s extreme thinness at these heights, the auroral light display cannot directly generate sound waves that reach the ground. Sound requires a denser medium to propagate, and any sound produced at such altitudes would dissipate. This distance also means a significant time delay between seeing the lights and hearing any associated noise.
However, scientific theories propose mechanisms for sound generation closer to the ground, linked to the electromagnetic disturbances that accompany auroral activity. One mechanism involves electrostatic discharges. During intense auroral events, electrical currents can induce static electricity on objects near the Earth’s surface. This accumulated charge can then intermittently discharge, creating sounds akin to crackling or hissing.
A primary explanation involves a temperature inversion layer in the lower atmosphere. On cold, clear nights, warmer air can trap colder air near the ground, allowing electrical charges to accumulate. When geomagnetic disturbances, linked to auroral activity, propagate downwards, they can trigger electrical discharges within this charged layer. These discharges, occurring at 70 to 100 meters (230 to 330 feet) above ground, produce the audible sounds. Thus, while not directly from the visible aurora, the sounds are a byproduct of the same geomagnetic forces, manifested in the lower atmosphere.
Modern Research and Verification
Modern scientific research has advanced our understanding of auroral sounds. Pioneering work by Professor Unto K. Laine and his team at Aalto University in Finland has provided instrumental evidence. Starting in the early 2000s, Laine employed sensitive recording equipment, including specialized microphones and very low frequency (VLF) antennae, to capture auroral acoustics.
In 2012, Laine’s team recorded distinct sounds, described as claps, crackles, and muffled bangs, during auroral displays. They triangulated the source to 70 to 100 meters (230 to 330 feet) above ground. This finding aligns with the temperature inversion layer hypothesis, suggesting that the sounds are generated by electrical discharges within this low-altitude atmospheric layer, triggered by geomagnetic activity.
Further research has shown a strong correlation between these recorded sounds and geomagnetic fluctuations, indicating that the sounds are a physical phenomenon linked to auroral activity. Studies have revealed that these sounds can even occur when there is no visible aurora, as long as the underlying geomagnetic disturbances and atmospheric conditions, such as a temperature inversion, are present.
Hearing auroral sounds remains a rare experience, requiring specific conditions. Observers need a quiet environment, far removed from man-made noise and light pollution, to detect these faint noises. The auroral display itself also needs to be intense, indicating strong geomagnetic activity. The sounds are subtle, typically 20 to 60 decibels, comparable to rustling leaves or a quiet conversation, making them easily masked by ambient noise. Not everyone will perceive these elusive sounds, even under ideal circumstances.