C. P. Haynes¹ and C. Millet²

¹UMR 7600, CNRS/Université Pierre et Marie Curie, Paris, France
²CEA, DAM, DIF, Arpajon, France

We perform a multicomponent sensitivity analysis of how the physical and dynamical parameters that characterize a meteor (in-fall) affect the ground overpressure and period of a plausible emitted N-wave signal. The nonlinear propagation model used throughout is based upon Whitham’s nonlinearization method which is modified to take into account a stratified atmosphere. We use sensitivity indices, derived using a Fourier Amplitude Sensitivity Test, to measure how the meteor parameters’ uncertainties affect the uncertainty in the overpressure and period of an emitted N-wave. The investigated parameters include the azimuth, entry angle, diameter, drag coefficient, density, and initial velocity of the meteor, as well as the atmosphere. The method is used to re-examine the crater-forming meteorite fall near Carancas, Peru (2007). We obtain good agreement between the simulated signals and observed waveforms. It is shown that ground overpressure uncertainty depends on the atmospheric uncertainties that are strongly correlated with the unknown trajectory, whereas the period is governed by the diameter uncertainties. Finally, we consider new waveform parameters that help characterize the meteor.

Reference
Haynes CP and Millet C (in press) A sensitivity analysis of meteoric infrasound. Journal of Geophysical Research – Planets, 118
[doi:10.1002/jgre.20116]
Published by arrangement with John Wiley & Sons

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Lorin S. Matthews¹, Babak Shotorban², and Truell W. Hyde¹

The coagulation of cosmic dust grains is a fundamental process which takes place in astrophysical environments, such as presolar nebulae and circumstellar and protoplanetary disks. Cosmic dust grains can become charged through interaction with their plasma environment or other processes, and the resultant electrostatic force between dust grains can strongly affect their coagulation rate. Since ions and electrons are collected on the surface of the dust grain at random time intervals, the electrical charge of a dust grain experiences stochastic fluctuations. In this study, a set of stochastic differential equations is developed to model these fluctuations over the surface of an irregularly shaped aggregate. Then, employing the data produced, the influence of the charge fluctuations on the coagulation process and the physical characteristics of the aggregates formed is examined. It is shown that dust with small charges (due to the small size of the dust grains or a tenuous plasma environment) is affected most strongly.

Reference
Matthews LS, Shotorban B and Hyde TW (in press) Cosmic Dust Aggregation with Stochastic Charging. The Astrophysical Journal
[doi:10.1088/0004-637X/776/2/103]

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Christian Klimczak^1,*, Carolyn M. Ernst², Paul K. Byrne¹, Sean C. Solomon^1,3, Thomas R. Watters⁴, Scott L. Murchie², Frank Preusker⁵, Jeffrey A. Balcerski⁶

¹Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, D.C., USA
²The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
³Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
⁴Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, D.C., USA
⁵German Aerospace Center, Institute of Planetary Research, Berlin, Germany
⁶Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, Ohio, USA

The volcanic plains that fill the Caloris basin, the largest recognized impact basin on Mercury, are deformed by many graben and wrinkle ridges, among which the multitude of radial graben of Pantheon Fossae allow us to resolve variations in the depth extent of associated faulting. Displacement profiles and displacement-to-length scaling both indicate that faults near the basin center are confined to a ~ 4-km-thick mechanical layer, whereas faults far from the center penetrate more deeply. The fault scaling also indicates that the graben formed in mechanically strong material, which we identify with dry basalt-like plains. These plains were also affected by changes in long-wavelength topography, including undulations with wavelengths of up to 1300 km and amplitudes of 2.5 to 3 km. Geographic correlation of the depth extent of faulting with topographic variations allows a first-order interpretation of the subsurface structure and mechanical stratigraphy in the basin. Further, crosscutting and superposition relationships among plains, faults, craters, and topography indicate that development of long-wavelength topographic variations followed plains emplacement, faulting, and much of the cratering within the Caloris basin. As several examples of these topographic undulations are also found outside the basin, our results on the scale, structural style, and relative timing of the topographic changes have regional applicability and may be the surface expression of global-scale interior processes on Mercury.

Reference
Klimczak C, Ernst CM, Byrne PK, Solomon SC, Watters TR, Murchie SL, Preusker F and Balcerski JA (in press) Insights into the subsurface structure of the Caloris basin, Mercury, from assessments of mechanical layering and changes in long-wavelength topography. Journal of Geophysical Research – Planets, 118
[doi:10.1002/jgre.20157]
Published by arrangement with John Wiley & Sons

Link to Article