Investigating the Relationship Between Bolide Entry Angle and Apparent Direction of Infrasound Signal Arrivals

Journal Article · Wed Jun 04 00:00:00 EDT 2025 · Pure and Applied Geophysics

DOI:https://doi.org/10.1007/s00024-025-03706-1· OSTI ID:2584031

Silber, Elizabeth Allaryce ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Infrasound sensing offers critical capabilities for detecting and geolocating bolide events globally. However, the observed back azimuths, directions from which infrasound signals arrive at stations, often differ from the theoretical expectations based on the bolide’s peak brightness location. For objects with shallow entry angles, which traverse longer atmospheric paths, acoustic energy may be emitted from multiple points along the trajectory, leading to substantial variability in back azimuth residuals. This study investigates how the entry angle of energetic bolides affects the back azimuth deviations, independent of extrinsic factors such as atmospheric propagation, station noise, and signal processing methodologies. A theoretical framework, the Bolide Infrasound Back-Azimuth EXplorer Model (BIBEX-M), was developed to compute predicted back azimuths solely from geometric considerations. The model quantifies how these residuals vary as a function of source-to-receiver distance, revealing that bolides entering at shallow angles, e.g., 10°, can produce average residuals of 20°, with deviations reaching up to 46° at distances below 1000 km, and remaining significant even at 5000 km (up to 8°). In contrast, bolides with steeper entry angles, e.g., > 60°, show smaller deviations, typically under 5° at 1000 km and diminishing to less than ~1° beyond 5000 km. These findings attest to the need for careful interpretation when evaluating signal detections and estimating bolide locations. This work is not only pertinent to bolides but also to other high-energy, extended-duration atmospheric phenomena such as space debris and reentry events, where similar geometric considerations can influence infrasound arrival directions.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0003525
• OSTI ID: 2584031
• Alternate ID(s): OSTI ID: 2585615
• Report Number(s): SAND--2025-08806J; 1773025
• Journal Information: Pure and Applied Geophysics, Journal Name: Pure and Applied Geophysics Journal Issue: 6 Vol. 182; ISSN 1420-9136; ISSN 0033-4553
• Publisher: Springer
• Country of Publication: United States
• Language: English

Related Subjects

Acoustics
Aeroacoustics
Diffraction
Electroacoustics
Geodesy
Geophysics
asteroid
bolide
infrasound
infrasound propagation
meteor
meteoroid
planetary defense
signal analysis