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Instrumental recording of electrophonic sounds from Leonid fireballs
Department of Physics, University of Zagreb, Zagreb, Croatia
Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky, USA
Centre Interdepartemental de Microscopie Electronique, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Cognitive Neuroscience Sector, International School for Advanced Studies (SISSA), Trieste, Italy
Department of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, Zagreb, Croatia
Faculty of Electrical Engineering and Computing, University of Zagreb, Zagreb, Croatia
Division of Materials Science, Rudjer Bošković Institute, Zagreb, Croatia
Department of Physics, EPFL, Lausanne, Switzerland
Electrophonic meteor sounds, heard simultaneously with the meteor appearance, are a longstanding problem due to their nonintuitive nature. Previous investigations have been undermined by lack of instrumental recordings. Here we present the first instrumental detection of electrophonic sounds obtained during the observation of 1998 Leonids from Mongolia. Two Leonid fireballs of brightness −6.5m and −12m produced short, low-frequency sounds, which were simultaneously recorded by microphones in a special setup and heard by different observers. Simultaneous measurements of electromagnetic ELF/VLF radiation above 500 Hz did not reveal any signal correlated to the electrophonic event. The lack of signal was explained by the low frequency of electrophones. We show that physical characteristics of Leonid electrophones cannot be completely explained by existing theories and that further theoretical refinement and observational work is needed. Finally, we tentatively suggest the possibility of stronger than expected coupling of fireballs with atmospheric charge dynamics and ionosphere.
Published 23 July 2002.
Citation: (2002), Instrumental recording of electrophonic sounds from Leonid fireballs, J. Geophys. Res., 107(A7), 1124, doi:10.1029/2001JA000310.
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