The aurora borealis, often called the Northern Lights, is one of the planet’s most spectacular light shows, painting the polar night sky with shimmering curtains of green and red. For centuries, this visual phenomenon has been accompanied by anecdotal reports of a faint, strange noise. The question of whether the aurora makes noise was long met with scientific skepticism, as the light display occurs too high in the atmosphere for sound to reach the ground. However, modern scientific investigation has confirmed that a rare, audible phenomenon does accompany intense auroral displays, but the sound is generated by a separate process than the light itself.
The Silent Display: How Light Is Generated
The visible aurora is born from the interaction between the sun and Earth’s atmosphere at extremely high altitudes. The sun constantly emits a stream of charged particles known as the solar wind, which travels until it encounters Earth’s magnetic field. This magnetic field acts as a shield, funneling most of the charged particles, primarily electrons and protons, toward the polar regions.
When these high-energy particles collide with atoms and molecules in the upper atmosphere, they excite the atmospheric gases, causing them to glow. Oxygen atoms typically emit the familiar green light, while nitrogen molecules can produce hints of blue, pink, and purple. The light display usually begins about 60 miles (100 kilometers) above the surface, extending upward to over 185 miles (300 kilometers).
This immense altitude is why the visual aurora is inherently silent to observers on the ground. Sound waves require a medium, like air, to travel, and the atmosphere at these heights is too thin to effectively transmit acoustic energy. Any sound generated within the glowing aurora would dissipate long before it could travel the tens of miles down to the ground. Therefore, the high-altitude light show itself creates no audible sound for a human observer.
Confirming the Audible Aurora
For generations, people in northern latitudes, including the Sami people of Finland, described hearing faint sounds alongside bright auroras. Scientists often dismissed these accounts as folklore, auditory illusions, or psychological effects. Skeptics argued the sounds were either the crackling of frost or the observer’s imagination.
The consistent reports spurred dedicated research to bridge the gap between anecdotal evidence and scientific proof. This culminated in scientific validation in the early 2000s, primarily through the work of acousticians in Finland. Using specialized equipment, researchers captured and recorded the elusive sounds, typically described as quiet hissing, faint crackling, or popping noises.
The studies confirmed the sounds were real and coincided precisely with intense geomagnetic activity, which also causes bright auroras. This established that the audible phenomenon was not an illusion but a rare, low-intensity acoustic event. The confirmed reality of the sound shifted research focus from if the aurora made noise to how a simultaneous, audible effect could be generated so close to the observer.
The Low-Altitude Sound Mechanism
The confirmed sounds are now understood to be an “electrophonic” phenomenon, created by electrical effects very close to the observer, rather than coming from the high-altitude lights. The mechanism begins with the same solar wind activity that drives the visual aurora, causing rapid, intense fluctuations in Earth’s magnetic field. This geomagnetic disturbance simultaneously induces strong electrical fields near the ground.
Under specific atmospheric conditions, these induced electrical fields generate sound. The necessary condition is often a low-altitude temperature inversion layer, which forms on clear, calm nights when warmer air traps colder air near the surface. This inversion layer acts as a boundary where electrical charges accumulate, with positive charges descending from above and negative charges rising from the ground.
The rapidly fluctuating electrical field caused by the intense aurora triggers a sudden discharge of these accumulated charges within or near the inversion layer. This discharge is a localized electrical event, similar to static electricity or a tiny spark, creating a measurable magnetic pulse and a sound pressure wave. These acoustic events have been triangulated to an altitude of only about 230 feet (70 meters) above the ground. This explains why the sound is heard immediately and without the delay expected from a source miles high.
The sound is not an echo or a direct product of the light, but a separate, ground-level electrical byproduct of the same solar activity that powers the light show. This localized discharge creates the faint crackling or hissing heard by an observer under perfect conditions: a strong auroral display, calm weather, and the presence of the temperature inversion layer.