Bulletin of the American Physical Society
2021 Annual Meeting of the APS Four Corners Section
Volume 66, Number 11
Friday–Saturday, October 8–9, 2021; Virtual; Mountain Daylight Time
Session E05: Atmospheric Physics, Geophysics, and Acoustics |
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Chair: Keith Ulmer, University of Colorado Boulder |
Friday, October 8, 2021 3:15PM - 3:39PM |
E05.00001: Probing Lightning Effects at the Edge of Space Invited Speaker: Caitano da Silva The lower ionosphere marks the separation between neutral and ionized regions of the Earth’s atmosphere, and has been colloquially referred to as the edge of space. The Earth and the ionosphere create a cavity that traps low-frequency electromagnetic waves, making long-range radio communications possible. Leveraging this phenomenology, the high variability of the lower ionosphere, the so-called ionospheric D region, has been extensively probed with ELF/VLF remote sensing. A byproduct of thunderstorms, transient luminous events (TLEs), have appeared as an opportunity for optical remote-sensing of the lower ionosphere-mesosphere system, by being not only a consequence of the electrical coupling of atmospheric regions, but also its thermometer. In this presentation, we review our group's recent efforts to probe the impacts of lightning in the lower ionosphere by remote sensing of sprites and their electromagnetic signatures [Contreras-Vidal et al., J. Geophys. Res. Atmos., 2021], and by looking at direct electron density changes measured by the Arecibo Observatory Incoherent Scatter Radar in coincidence with underlying thunderstorm activity [da Silva et al., Sci. Rep., 2021]. [Preview Abstract] |
Friday, October 8, 2021 3:39PM - 3:51PM |
E05.00002: Inferring physical parameters in ocean acoustic models using the Fisher information Michael Mortenson, Traci Neilsen, Mark Transtrum, David Knobles The Fisher information matrix (FIM) and the Cramer-Rao bound (CRB) are ubiquitous tools for quantifying uncertainty in multi-parameter models. However, the FIM involves derivatives of a forward model with respect to parameters that are difficult to estimate in ocean acoustic models. This work presents a methodology for accurately estimating derivatives using physics-based parameter preconditioning and Richardson extrapolation. The methodology is validated on a case study of transmission loss from a range-independent normal mode model in shallow ocean environments with a single sediment layer over a basalt basement. Five examples of sediment types ranging from mud to gravel are considered across frequencies over the 50--400 Hz band. Results demonstrate the utility of FIM and CRB analysis in quantifying both model sensitivities and parameter uncertainties, and in revealing parameter coupling in the model. This methodology is a general tool that can inform model selection and experimental design for inverse problems in different applications. [Preview Abstract] |
Friday, October 8, 2021 3:51PM - 4:03PM |
E05.00003: Global study of mid-mantle discontinuities by observations of multiple-ScS phases Rashni Anandawansha, Lauren Waszek, Benoit Tauzin The mid-mantle represents a significant transformation in Earth’s structure, rheology,and composition. In order to understand the thermal structure of the mantle and Earth’s deep dynamics we need to thoroughly study the seismic structure of the mantle transitions zone (MTZ), which represent a boundary between upper and lower mantle. As the pressure and temperature increases with the depth MTZ undergoes some discontinuities in seismic properties. The 410 km and 660 km depths correspond to major discontinuity jumps which occurs due to mineral phase transition from olivine to wadsleyite and from ringwoodite to bridgmanite and ferropericlase. Seismic tomography models have found that both down-going slabs and up-welling plumes become trapped in the mid-mantle. The underlying cause of deflection of material in the mid-mantle is not well understood. In this study, we use a new data-set collected from intermediate and deep earthquakes around the globe. This data set consist of long period, multiple-ScS phases and their reverberations due to MTZ discontinuities. All the data undergo a similar forward modeling method. We generate maps of the global discontinuities using an “adaptive stacking” parameterisation technique, which accounts for topography, noise, and data coverage. [Preview Abstract] |
Friday, October 8, 2021 4:03PM - 4:15PM |
E05.00004: Spectrum and Acoustical Analysis of the Piano Using Mathematical and Physical Simulations Eugene Hong Each musical instrument has unique acoustic characteristics such as resonance, volume, timbre, and different harmonics with different energies. String instruments show specifically strong first and third harmonic components and woodwind and brass have more energy focused in a certain harmonic than in the first harmonic frequency. While experimenting on the Piano, the characteristics of the harmonic components were studied. In this paper, the spectral analysis of the instrument piano was carried out using mathematics and physics principles. The wave forms and spectrums of each instrument were compared to effectively analyze the unique acoustic characteristics of Piano. In the spectral analysis, it is interesting to notice that most of the harmonics are found as equally spaced components. Also, the power or energy of all the harmonics change over time, but the pitch does not change a lot, so the frequencies of the spectral lines are constant. We found that Piano generates a more pure tone than the Violin, and generates more fuzzy tone compared to the other instruments analyzed in this paper. Because the entire plot was too lengthy to model with the Fast Fourier Transform (FFT) function in MATLAB, the analysis on a certain period of the plucked note has been performed. [Preview Abstract] |
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