[Meteor-Scatter] electrophonic meteor "sounds"

[Shelby Ennis, W8WN]

Date: Mon, 11 Nov 2002 03:18:00 -0500 (EST)
From: Dejan Vinkovic <dejan@ccs.uky.edu>
Subject: (meteorobs) Electrophonic Sounds - Review of witness reports

Dear meteor observers,

the upcoming Leonids provide a great opportunity to potentially witness
one very rare astronomical phenomenon: electrophonic sounds from meteors.

In contrast to "ordinary" meteor sounds, which have a time lag between the
sound and the meteor appearance, the electrophonic (or anomalous) meteor
sounds appear simultaneously with the meteor.

It is so little known about the phenomenon that witness reports still play
an important role in studying the phenomenon. Thus, two years ago we
started with the Global Electrophonic Fireball Survey (GEFS), a project
that collects witness reports of this rare phenomenon.

The first review of almost 100 reports collected by GEFS is now publicly
available at: http://www.gefsproject.org/publications

The witness reports are also available at the same web-address (for
further details see our review paper).

The result of statistical analysis revealed some interesting and
previously unknown aspects of the phenomenon. Basically, a new overall
picture of the phenomenon emerged from this study, with very important
consequences for the theoretical efforts since the current theories can
not explain these results.

The paper is submitted to WGN, the Journal of the IMO, and the abstract is
attached in the end of this e-mail. For more details visit the project's
web-pages at www.gefsproject.org, and, in a case you hear such a sound
during the Leonids, please, submit your report at:
http://www.gefsproject.org/form

Thank you and good luck with your Leonid observations!

   Dejan Vinkovic

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Vinkovic, D., Garaj, S., Lim, P. L., Kovacic, D., Zgrablic, G., Andreic,
Z. "Global Electrophonic Fireball Survey: a review of witness reports - I.
", submitted to WGN

ABSTRACT: "Despite more than 300 years since its first scientific
           description, the phenomenon of electrophonic sounds from meteors
           are still eluding complete physical explanation. According to
           the accepted knowledge, the sound itself is created by strong
           electric fields on the ground induced by the meteor.
           Nonetheless, there is no convincing theory that can fully
           explain how a meteor can generate such a strong electric
           field. Extreme rareness of the phenomenon has prevented a
           substantial experimental work so far; thus, consequently, it
           remains on the margins of scientific interest. This is quite
           unfortunate since these electric fields suggest existence of a
           highly complex electromagnetic coupling and charge
           dynamics between the meteors and the ionosphere.
           Therefore, the existing theoretical work relies mostly on the
           witness reports. The Global Electrophonic Fireball Survey
           (GEFS) is the first systematic survey of witness reports of
           these sounds with a standardized questionnaire designed
           exclusively for this phenomenon. Here we present the overall
           picture of the phenomenon that emerged after almost 100
           reports collected by GEFS. It becomes clear now that the lover
           meteor brightness limit is about -2m, suggesting a bias in the
           existing electrophonic sounds catalogues toward brighter
           meteors. In contrast to the current belief that such low
           brightness electrophonic meteors produce transient sounds,
           we find that they can also produce sustained sounds. The
           current theories can not accommodate these results. We
           revive the old idea that the electrophonic sounds can be
           created by the corona discharge mechanism, in addition to the
           existing prevalent suggestion of resonant vibration of objects
           on the ground. "

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Department of Physics and Astronomy  | Center for Computational Sciences
University of Kentucky               | University of Kentucky
177 CP-bldg                          | 325 McVey Hall
Lexington, KY 40506-0055             | Lexington, KY 40506-0045
e-mail: dejan@pa.uky.edu             | e-mail: dejan@ccs.uky.edu
http://www.pa.uky.edu/~dejan         | http://www.ccs.uky.edu/~dejan