MMAE Seminar - Dr. Seebany Datta-Barua - Mapping Material Transport in the Upper Atmosphere
Armour College of Engineering's Mechanical, Materials & Aerospace Engineering Department will welcome Dr. Seebany Datta-Barua, Assistant Professor of Mechanical and Aerospace Engineering, on Wednesday, January 18th, to present her lecture, Mapping Material Transport in the Upper Atmosphere.
Abstract
In 2003, water vapor exhaust and iron that ablated during a space shuttle launch reached the lower thermosphere, Earth's neutral atmosphere above 85 km dominated by neutral gas dynamics and driven by diurnal heating. Two to three days later noctilucent clouds appeared in the upper atmosphere, and the iron was detected over the Antarctic [Stevens et al., 2005]. These observations raise an intriguing question: was there structuring in the thermospheric fluid that could have predicted the transport?
Coherent structuring is known to occur in the upper atmosphere, e.g., in the form of auroral arcs and curls in the ionosphere, the charged particle layer embedded in the thermosphere subject to electrodynamic forcing. Identification of ionosphere-thermosphere (IT) structuring requires sustained observation of 2D or 3D flow fields over broad regions: distributed remote sensing and data assimilation. Together these provide the means to apply advanced fluid advection analysis for predictive ability in material transport in the upper atmosphere.
In this work, I present recent efforts in distributed sensing and data assimilation. The Scintillation Auroral GPS Array (SAGA) consists of six closely spaced Global Positioning System (GPS) receivers designed to monitor fluctuations in signal amplitude and phase. Through spaced-receiver cross-correlation techniques, the
array is able to sense motion of the ionospheric irregularities that cause scintillation. The data assimilation method Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE) ingests GPS-derived electron densities and Fabry-Perot interferometer (FPI) measurements of line-of-sight thermospheric neutral winds for the first time to provide regional estimates of horizontal neutral winds and ion convection.
Distributed sensing and data assimilation in turn pave the way to a method of fluid analysis gaining widespread attention in geophysical science: Lagrangian Coherent Structuring (LCS). In the Lagrangian frame, which flows with the particles in contrast to an Eulerian fixed mesh frame, barriers in material transport can be numerically and objectively identified. Given a sequence of 2D flow fields, particles are traced and their maximum stretching after a finite time quantified through the finite time Lyapunov exponent (FTLE). The manifolds of maximum FTLE over the domain define barriers within the flow domain across which fluid material cannot cross. I show that the location of global thermospheric LCSs are expected to be at mid-to-high latitudes and respond to electrodynamic forcing, based on the empirical Horizontal Wind Model (HWM 2014). Such analysis can in future be applied to data-derived flow fields to investigate IT material transport such as that of the space shuttle plume.
Biography
Seebany Datta-Barua is an Assistant Professor of Mechanical and Aerospace Engineering at Illinois Institute of Technology in Chicago. She received her B.S. in physics, and M.S. and Ph.D. (2008) degrees in aeronautics and astronautics, from Stanford University. Before joining IIT, she was a Research Engineer at ASTRA and then an Assistant Professor at San Jose State University.
Prof. Datta-Barua researches using Global Navigation Satellite Systems (GNSS) for remotely sensing the ionosphere, using tomography and data assimilation of these measurements for improved ionospheric and thermospheric prediction of dynamics, and in mitigating upper atmospheric effects on GPS-based navigation systems.
Dr. Datta-Barua has received the NSF CAREER award. She is on the NSF CEDAR Science Steering Committee and is an Early Career Representative for Commission G of URSI. She is an Associate Editor of Radio Science and was recognized as an Outstanding Reviewer for Space Weather and Navigation.