Characteristics of thermospheric infrasound predicted using ray tracing and weakly non-linear waveform analyses

Blom, Philip; Waxler, Roger

doi:10.1121/10.0004949

Cited by 15 publications

(18 citation statements)

References 27 publications

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“…The integrated path of an AW can be approximated using the ray tracing methods provided by the InfraGA/GeoAc package provided by Los Alamos National Laboratory for the purpose of modeling long range infrasound propagation. The software can be downloaded at https://github.com/LANL-Seismoacoustics/infraGA, and further details can be found in (P. Blom & Waxler, 2012; P. Blom & Waxler, 2017; P. Blom, 2019; P. Blom & Waxler, 2021). InfraGA is capable of 2D, 3D‐cartesian and 3D‐spherical calculations of infrasound ray tracing and waveform evolution well into the thermosphere.…”

Section: Expected Arrival and Frequency Structurementioning

confidence: 99%

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Identification of Acoustic Wave Signatures in the Ionosphere From Conventional Surface Explosions Using MF/HF Doppler Sounding

2022

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We present an experiment to detect one ton TNT‐equivalent chemical explosions using pulsed Doppler radar observations of isodensity layers in the ionospheric E region during two campaigns. The first campaign, conducted on 15 October 2019, produced potential detections of all three shots. The detections closely resemble the temporal and spectral properties predicted using the InfraGA ray tracing and weakly nonlinear waveform propagation model. Here the model predicts that within 6.5–7.25 min of each shot a waveform peaking between 0.9 and 0.4 Hz will impact the ionosphere at 100 km. As the waves pass through this region, they will imprint their signal on an isodensity layer, which is detectable using a Doppler radar operating at the plasma frequency of the isodensity. Within the time windows of each of the three shots in the first campaign, we detect enhanced wave activity peaking near 0.5 Hz. These waves were imprinted on the Doppler signal probing an isodensity layer at 2.785 MHz near 100 km altitude. Despite these detections, the method appears to be unreliable as none of the six shots from the second campaign, conducted on 10 July 2020 were detected. The observations from this campaign were characterized by an increased acoustic noise environment in the microbarom band and persistent scintillation on the radar returns. These effects obscured any detectable signal from these shots and the baseline noise was well above the detection levels of the first campaign.

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Section: Expected Arrival and Frequency Structurementioning

confidence: 99%

“…The integrated path of an AW can be approximated using the ray tracing methods provided by the InfraGA/GeoAc package provided by Los Alamos Blom & Waxler, 2021). InfraGA is capable of 2D, 3D-cartesian and 3D-spherical calculations of infrasound ray tracing and waveform evolution well into the thermosphere.…”

Section: Expected Arrival and Frequency Structurementioning

confidence: 99%

Identification of Acoustic Wave Signatures in the Ionosphere From Conventional Surface Explosions Using MF/HF Doppler Sounding

2022

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“…After this first wave train, a later arrival can in many cases be observed between Blom & Waxler, 2021). Time after explosion (min) A closer look at Figure 3 further reveals that several of the events feature an arrival between the stratospheric and thermospheric arrivals, see also Gibbons et al (2019, Fig.…”

Section: Infrasound Dataset and Signal Pre-processingmentioning

confidence: 72%

“…The typical yield of Hukkakero explosions is presumed to be approximately 20 ton of TNT equivalent . According to the • As the initially generated shock wave propagates, it experiences attenuation and becomes distorted due to non-linear propagation effects, which become more prominent with increasing height due to decreasing atmospheric density with altitude Blom & Waxler, 2021). One of the distortion features associated with non-linear propagation is period lengthening, which occurs since positive and negative phases of the pressure wave travel at slightly different speed .…”

Section: Effective Sound Speed Retrievalmentioning

confidence: 99%

Probing gravity waves in the middle atmosphere using infrasound from explosions

Vorobeva

Assink

Espy

et al. 2023

Preprint

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This study uses low-frequency, inaudible acoustic waves (infrasound) to probe wind and temperature fluctuations associated with breaking gravity waves in the middle atmosphere. Building on an approach introduced by Chunchuzov et al., infrasound recordings are used to retrieve effective sound-speed fluctuations in an inhomogeneous atmospheric layer that causes infrasound backscattering. The infrasound was generated by controlled blasts at Hukkakero, Finland and recorded at the IS37 infrasound station, Norway in the late summers 2014 - 2017. Our findings indicate that the analyzed infrasound scattering occurs at mesospheric altitudes of 50 - 75 km, a region where gravity waves interact under non-linearity, forming thin layers of strong wind shear. The retrieved fluctuations were analyzed in terms of vertical wave number spectra, resulting in approximate kz-3 power law that corresponds to the “universal“ saturated spectrum of atmospheric gravity waves. The kz-3 power law wavenumber range corresponds to vertical atmospheric scales of 33 - 625 m. The fluctuation spectra were compared to theoretical gravity wave saturation theories as well as to independent wind measurements by the Saura medium-frequency radar near Andøya Space Center around 100 km west of IS37, yielding a good agreement in terms of vertical wavenumber spectrum amplitudes and slopes. This suggests that the radar and infrasound-based effective sound-speed profiles represent low- and high-wavenumber regimes of the same “universal“ gravity wave spectrum. The results illustrate that infrasound allows for probing fine-scale dynamics not well captured by other techniques, suggesting that infrasound can provide a complementary technique to probe atmospheric gravity waves.

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“…The absence of codas later in the afternoon suggests that a temperature inversion in the morning may enhance the effect of topographic interaction. With no temperature inversion in place, a greater portion of a given shot's energy is expected to refract upwards rather than traveling along the surface (Blom & Waxler, 2021).…”

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confidence: 99%

Topographically Scattered Infrasound Waves Observed on Microbarometer Arrays in the Lower Stratosphere

Bird

Lees

Kero

et al. 2022

Earth and Space Science

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A wide range of natural and anthropogenic events produce infrasound, acoustic waves with a frequency below 20 Hz (the approximate lower limit of human hearing). Infrasound can be used to monitor a variety of sources, including earthquakes (e.g., Arrowsmith et al., 2012), volcanic eruptions (e.g., Johnson & Ripepe, 2011, ocean processes (e.g., Fricke et al., 2014), urban activity (e.g., Bird et al., 2021), and nuclear or chemical explosions (e.g., Che et al., 2009;Pasyanos & Kim, 2019). The bulk of infrasound research focuses solely on data from ground-based sensors, but a growing area of study considers airborne stations (Bowman, 2021). Recordings from infrasound microphones attached to balloons, aerostats, or other similar crafts have been used to interrogate numerous sources, including microbaroms (Bowman & Lees, 2015), volcanism (Jolly et al., 2017, chemical explosions (Bowman et al., 2014), sonic booms (Veggeberg, 2012), and ground shaking (Krishnamoorthy et al., 2018). Relative to ground stations, balloon-borne sensors appear to mitigate background noise from wind, recording subtle, lower-amplitude details (Young et al., 2018) and at times record signals not observed on groundbased arrays (Bowman & Lees, 2017).The majority of the studies cited above included only one sensor per floating station. However, we designed our balloons to include microbarometers separated by 100 m, which enabled the elevation angle of incoming acoustic signals to be calculated (e.g., Wescott, 1964). The distance the plane wave travels between arrivals at each payload is given by the product of the lag time between arrivals at the lower and upper sensors and the speed of sound. Considering the right triangle formed with this distance acting as the opposite leg a and the tether length

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Characteristics of thermospheric infrasound predicted using ray tracing and weakly non-linear waveform analyses

Cited by 15 publications

References 27 publications

Identification of Acoustic Wave Signatures in the Ionosphere From Conventional Surface Explosions Using MF/HF Doppler Sounding

Identification of Acoustic Wave Signatures in the Ionosphere From Conventional Surface Explosions Using MF/HF Doppler Sounding

Probing gravity waves in the middle atmosphere using infrasound from explosions

Topographically Scattered Infrasound Waves Observed on Microbarometer Arrays in the Lower Stratosphere

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