Auroral Sounds The phenomenon of Auroral Sounds or Auroral Chorus

Auroral Sounds
The phenomenon of Auroral Sounds or Auroral Chorus related to the Northern Lights has been a topic of many discussions and researches all over the world for several years now. The sound has been described as unusual noises like the crinkling sound of cellophane cover, radio static or the sound made when some small animal rushes through dry leaves or grass.
How Auroral Sounds are born
Professor Unto K. Laine of Aalto University heading a group of research team in 2012 came out with the proof that the Auroral Sounds attributed to Northern Lights had the source located at about seventy meters altitude which is very close to earth. Professor Laine has further identified the mechanism causing the sound by combining the measurements of temperature profiles taken by the Finnish Meteorological Institute with his own measurements. As per the new theory on inversion layer, the strange sounds connected to Northern Lights are created when the geomagnetic storm releases the charges collected in the inversion layer of the atmosphere.
The Mechanism of Auroral Sounds
According to Dr. Laine, the temperatures are lower at the higher altitudes compared to lower levels. But the opposite happens when temperatures drop below zero usually when the weather is calm and clear in the evenings and nights. Air becomes cooler near earth’s surface and warmer at higher altitudes. The warmer air, moves up carrying negative charges present at the ground level, to higher levels where colder layers are present, but the inversion layer acts as a preventive lid and does not allow the movement. The colder air which is present above the inversion layer is positively charged. Then the accumulated charges are discharged due to a geomagnetic storm causing sparks, Auroral Sounds and magnetic pulses that can be measured and recorded.
Dome Over Village
Dr. Laine’s experiments and were carried out on two days on the 17th and 18th of March 2013. During this period, there were unusually enchanting Northern lights in Southern Finland. To arrive at his conclusions, Dr. Laine had to carry out several hundreds of experiments of the sound phenomenon in Fiskers at a temperature of -20 degree centigrade. Summarizing, Professor Laine says that even a mild wind can stop the creation of inversion layer. This would mean that there will not be any sound. He further adds that the effect of inversion layer had been felt by him even as boy when he was residing in Ostrobothnia. He had observed that during winter, in calm weather, the smoke emitted from the chimneys of cottages would raise straight upwards vertically and then would stop suddenly and spread horizontally like a dome above the village.
Concluding, Professor Laine stresses that his theory does not say that there are no other mechanisms causing this phenomenon, but the three mysteries connected to the Auroral Sounds are all explained in his hypothesis for the first time. We can thus understand not only the mechanism causing the auroral sound, but also how we are able to hear the same when the auroral light source is as far away as 80-100 kms. It shows how we can hear the Auroral Sounds from 75 meters at the same time as we see the light in only 0.2 seconds.