AURORAL CRACKLING SOUNDS AND SCHUMANN RESONANCES

摘要

Observations of unusual sounds like claps, snaps, and cracklings from a serene sky under actively moving, bright aurora borealis have been reported during a long history. Since year 2000 the auroral sounds have been studied in Finland. In 2011 a sound source associated with the aurora was localized for the first time in the sky approximately 70 meters from the ground. To accommodate for the surprisingly low altitude of the source, a hypothesis that the sounds are produced by corona discharges in a temperature inversion layer at the observed altitude was published in 2016. The focus of the present paper is in the acoustic analysis of the crackling sounds that are sequences with complex temporal structures. It is shown that the sounds share similar rhythmical patterns, which are connected to the electromagnetic resonances in the atmosphere, also known as the Schumann resonances.