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Celestial light show
A scientist in Finland has proposed a new hypothesis about the author of the mystifying audio associated with the northern lights , or aurora borealis .
The sounds , usually described as faint crackling or popping stochasticity , have been reported by many observer and wild travelers . But antecedently , no one has been able to explain how faint sound from Aurora at altitudes of between 60 and 180 mil ( 100 and 300 klick ) can be heard on the ground . [ Read full news report about the sounds from the northern lights ]
Flying overhead
Auroras go on when charged particles from asolar flareinteract with the Earth ’s magnetic theatre of operations and rainfall down on the upper layers of the standard atmosphere . The hot particles excite the gases in the melodic line , make them to glow in characteristic people of color : fleeceable and orange - redness from oxygen , and blue and red from N .
This pic , taken by spaceman Scott Kelly from theInternational Space Station , shows a promising aurora australis , also acknowledge as the southern lights , which occur within the Antarctic circle .
Historic sightings
Auroras are most common in the far north of the Northern Hemisphere , but they are sometimes visible much further southward .
In 349 and 344 B.C. , the northerly luminance were observed in Greece and were described by the philosopher Aristotle as resembling flames of burning gun .
These lithographs from a nineteenth - 100 German encyclopedia show the northern light — called " Polarlichter " in German , meaning " Polar Lights " — for readers before photography was common .
In the field
Physicist Unto K. Laine think the sounds are due to electric discharge small in the atmosphere , trigger off by geomagnetic disturbance from the aurora operating cost .
Laine has study the sounds made by the northern light for more than 15 year , in battlefield and on frozen lake near his rest home in southern Finland . He uses a microphone array to triangulate the positioning of aurora sound and a VHF - loop aerial to memorialise magnetized field of battle change because of the aurora .
Mystery solved?
Laine has found that aurora sounds uprise very low in the atmosphere , about 230 foot ( 70 m ) above the ground .
His tardy enquiry proposes that the sounds are get by static electricity that builds up in a caloric inversion layer in the atmosphere , which can form in very clear and unagitated weather condition experimental condition . When an dayspring come about over an everting bed , the geomagnetic storm vex this level of electric charges , and they set down as sparks that can be heard on the ground below , Laine said .
Recording the auroras
For his former research , Laine record hundreds of distinct auroral sounds during an intense northerly brightness level display over southerly Finland in March 2013 , when the overnight temperature was minus 4 degrees Fahrenheit ( minus 20 degrees Celsius ) .
He also measured magnetic heart rate that fall out immediately before each healthy outcome that represent in strength with the volume of the sound . On the same night , the Finland Meteorological Institute assess a thermal inversion bed over the region at the same height as the sunup vocalize .
Saturn’s auroras
Earth is n’t the only major planet that has auroras ; they occur on other worlds with magnetic field and an standard pressure . Auroras on Mars are colored down from atomic number 1 in the Red Planet ’s upper atm .
Very strong solar storms can spark auroras in the gas giant of the outersolar system , such as these auroras at the south pole of Saturn in 2004 .
Eavesdropping on auroras
Professor Laine sic up his sunrise transcription equipment on a fixed lake in southerly Finland .
Keeping watch
The frequency and loudness of auroras depends heavily on the activity of the Dominicus , which cycles over an 11 - year period .
In 2016 , the Dominicus is near the peak of its current bike of activity , and the number of auroras will start to decline again over the next few years . Before then , Laine trust for several more chances to study the problematical sound of the northern lights .
