Sounds of Northern Lights Are Born Close to Ground
Researchers at Aalto University in Finland have located where the sounds associated with the northern lights are created. The source of the auroral sounds that have been described in folktales and by wilderness wanderers was recently discovered. It has been found that they are formed about 70 meters above the ground level in the measured case.
Researchers were able to locate the sound sources by installing three separate microphones in an observation site where the auroral sounds were recorded. The sounds captured by the microphones were then compared and they were able to determine the location of the sound source. The aurora borealis had been seen at the observation site. A typical pattern of the northern lights episodes was shown by the simultaneous measurements of the geomagnetic disturbances.
Professor Unto K. Laine from Aalto University described it this way, "Our research proved that, during the occurrence of the northern lights, people can hear natural auroral sounds related to what they see. In the past, researchers thought that the aurora borealis was too far away for people to hear the sounds it made.
This is true. However, our research proves that the source of the sounds that are associated with the aurora borealis we see is likely caused by the same energetic particles from the sun that create the northern lights far away in the sky. These particles or the geomagnetic disturbance produced by them seem to create sound much closer to the ground."
Details about how the auroral sounds are created are still a mystery to the researchers because the sounds do not occur regularly when the northern lights are seen. The recorded, unamplified sounds are similar to crackles or muffled bangs which last for only a short period of time. Others have described them as distant sounds and sputters. Because of these different descriptions, it is suspected that there are several ways that these auroral sounds are formed. Some of these sounds are so soft that it is very difficult to distinguish them from ambient noise.
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