Northern lights have fascinated people for thousands of years – today researchers understand a secret about the natural spectacle more precisely: It is the strange noises that occur during otherwise quiet and clear aurora nights.
Scientists have long puzzled over whether the sounds could actually come from the northern lights. Finnish acoustician Unto Laine from Aalto University in Helsinki has been researching sounds for almost 20 years. In a new study, he recorded and analyzed the sounds made during an aurora display in January 2022.
The recordings show that the noises can be as diverse as the light phenomena themselves. While some sound like short pulses, others sound like gossips followed by echo-like sounds.
The researcher explains the origin of the aurora sounds as follows: Actually, these are electrical charge noises that only appear under certain weather conditions. For them to occur, it doesn’t just need an electromagnetic solar storm on Earth – the cause of auroras. There must also be a so-called inversion weather situation. The air in the higher layers is warmer than the air near the ground. The noise is produced in the layer about 70 to 100 meters above the ground, where the cold air meets the warm air. In this area, an electric charge occurs that interacts with the aurora’s electromagnetic field.
In his study, Laine also reports that the sounds can occur even when the auroras are not appearing.
“Aurora sounds are created in a different process than aurora lights. Nevertheless, both have the same geomagnetic background, which causes the synchronicity of the two phenomena,” reports Unto Laine in his study.
Source: Researchgate