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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. A7, 1124, doi:10.1029/2001JA000310, 2002

Instrumental recording of electrophonic sounds from Leonid fireballs

Goran Zgrablić

Department of Physics, University of Zagreb, Zagreb, Croatia


Dejan Vinković

Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky, USA


Silvija Gradečak

Centre Interdepartemental de Microscopie Electronique, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland


Damir Kovačić

Cognitive Neuroscience Sector, International School for Advanced Studies (SISSA), Trieste, Italy


Nikola Biliškov

Department of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, Zagreb, Croatia


Neven Grbac

Faculty of Electrical Engineering and Computing, University of Zagreb, Zagreb, Croatia


Željko Andreić

Division of Materials Science, Rudjer Bošković Institute, Zagreb, Croatia


Slaven Garaj

Department of Physics, EPFL, Lausanne, Switzerland


Abstract

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.

Index Terms: 6245 Planetology: Solar System Objects: Meteors; 2435 Ionosphere: Ionospheric disturbances; 6929 Radio Science: Ionospheric physics (2409); 2411 Ionosphere: Electric fields (2712).

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Citation: Zgrablić, G., D. Vinković, S. Gradečak, D. Kovačić, N. Biliškov, N. Grbac, Ž. Andreić, and S. Garaj (2002), Instrumental recording of electrophonic sounds from Leonid fireballs, J. Geophys. Res., 107(A7), 1124, doi:10.1029/2001JA000310.