Photoacoustic Sounds from Meteors

Area of Science:

• * Acoustics and atmospheric physics.
• * Electromagnetism and optical phenomena.

Background:

• * Concurrent sounds from bright meteors (fireballs) are observed simultaneously with their light.
• * Traditional acoustic propagation from the upper atmosphere cannot explain the timing of these sounds.
• * Previous hypotheses involving radio frequency (RF) emissions lack strong experimental validation.

Purpose of the Study:

• * To investigate the photoacoustic coupling mechanism as the cause of meteor-associated sounds.
• * To provide experimental and numerical evidence supporting this new hypothesis.
• * To explain the generation of audible sound from meteor light.

Main Methods:

• * Analysis of recent photometric measurements of fireballs, focusing on millisecond flares and high-frequency brightness oscillations (≥40 Hz).
• * Development of numerical models to simulate the photoacoustic effect.
• * Calculation of sound pressure levels (SPL) generated by modulated light interacting with dielectric materials.

Main Results:

• * Fireball photometry reveals significant brightness oscillations at frequencies relevant to sound generation.
• * Numerical models demonstrate that modulated light can cause radiative heating of materials like hair and clothing.
• * Calculations indicate that meteors of -12 brightness can produce sounds around 25 dB SPL via photoacoustic coupling.

Conclusions:

• * Photoacoustic coupling, driven by modulated meteor light, is a viable mechanism for generating concurrent sounds.
• * This mechanism offers an alternative explanation for the longstanding mystery of fireball sounds.
• * The intensity and modulation frequency of light from bright meteors are key factors in sound production.