The question of whether the aurora borealis makes noise touches on one of the most enduring mysteries of the northern lights. For centuries, observers standing beneath the shimmering curtains of green and red have reported a distinct crackling, hissing, or popping sound, as if the sky itself were whispering or snapping. Modern science has largely confirmed that these sounds are real, though they are remarkably subtle and fleeting, occurring close to the ground rather than in the high-altitude vacuum where the aurora's primary display unfolds.
The Historical Debate and Anecdotal Evidence
Historical accounts are filled with vivid descriptions of auroral noise, dating back to the observations of ancient Greek philosopher Aristotle and extending through the detailed journals of 18th and 19th-century explorers. Indigenous cultures across the Arctic wove these sounds into their folklore, often interpreting them as the voices of spirits or the result of spirits playing ball with a walrus skull. This long-standing body of anecdotal evidence was so compelling that it prompted serious scientific investigation, yet for a long time, the mainstream scientific community was skeptical, partly because the displays high in the ionosphere seemed too remote to produce audible sound directly at ground level.
Scientific Explanations and Theories
How can a phenomenon occurring tens of kilometers above the Earth produce a sound we can hear? The most plausible theory involves the Earth's magnetic field and the properties of the charged particles that interact with it. The aurora is a collisionless plasma, meaning the charged particles rarely bump into each other or the neutral gas molecules we hear. However, near the ground, the rapidly moving particles can induce an electrical charge on objects, creating a phenomenon known as the "electrostatic discharge" theory. This can cause the air around rocks, plants, or even fur to ionize, resulting in a tiny, sharp crackle.
VLF (Very Low Frequency) Waves and EM Pumping
A more complex mechanism involves electromagnetic waves, specifically Very Low Frequency (VLF) waves generated by the aurora itself. These waves can travel along the Earth's magnetic field lines and reach the lower atmosphere. When they interact with objects that have a different electrical potential, such as a long wire, a tree, or even a person, they can cause a phenomenon called "electromagnetic pumping." This induces a current that can lead to the micro-explosions of air molecules, creating the popping and crackling sounds. This theory elegantly explains why the noise is often localized and seems to move with the observer.
Characteristics of the Sound
The noise associated with the aurora is not a continuous roar or a musical melody. Descriptions from reliable witnesses consistently point to a sharp, brief, and elusive audio signature. It is most often reported as a crackling, hissing, or sizzling sound, similar to the static on a radio or the noise of frying fat. The volume is typically faint, requiring the listener to be very still and quiet, often in a state of heightened anticipation. It is rarely described as a dull thump or a loud boom, which helps distinguish it from other, more mundane noises like ice cracking or settling timber.
Modern Verification and Recordings
Advances in technology have allowed researchers to finally capture and verify the sounds definitively. In 2012, a Finnish geomagnetic researcher recorded an auroral event using a suite of microphones placed in a forest. The audio clearly picked up the high-frequency crackles and pops, and by analyzing the timing of the sounds relative to the visible aurora, scientists could confirm the correlation. These recordings provided the crucial empirical evidence needed to move the phenomenon from the realm of myth and mystery into the domain of established atmospheric physics, validating the experiences of countless observers.
