AE 590 Seminar Speaker: Sedina Tsikata - Stability and Time-Resolved Dynamics of Fluctuations in Magnetized Electric Propulsion Plasmas

Abstract:
Magnetized electric propulsion plasmas exhibit broadband, multiscale fluctuations that influence cross-field transport and discharge dynamics. Although significant progress has been made in identifying the underlying instabilities, their temporal evolution and interactions remain difficult to characterize from frequency spectra alone. This work examines two complementary approaches to understanding fluctuation dynamics and stability.

First, dispersion relation analysis is used to investigate unstable wave branches and growth rates under conditions relevant to an applied-field magnetoplasmadynamic thruster prototype. The analysis identifies potentially unstable modes accessible to non-invasive diagnostics and examines their sensitivity to plasma parameters, particularly the applied magnetic field.

Second, time-resolved coherent Thomson scattering measurements in a Hall thruster are analyzed to characterize the statistical and phase dynamics of electron density fluctuations at selected spatial scales. Analysis of isolated spectral modes examines their amplitude, instantaneous frequency, frequency wandering, and phase coherence over successive time windows. The results reveal evolving fluctuation states in which mode amplitude, frequency, and phase organization do not necessarily vary together. In particular, substantial fluctuation amplitudes can persist as phase coherence decreases, while frequency drift and enhanced frequency variability accompany changes in mode organization. 

Together, these approaches illustrate how linear stability analysis and time-resolved statistical diagnostics can provide complementary insights into instability-driven fluctuations, their nonlinear evolution, and their potential implications for transport in magnetized electric propulsion plasmas.

Bio:
Sedina Tsikata is an Associate Professor in Aerospace Engineering at the Georgia Institute of Technology. Her research concerns the fundamental nature and applications of magnetized plasmas, with a focus on the development of advanced diagnostics, analysis methods, control, and new plasma devices. This research has been applied to the study of instabilities and electron features in Hall plasma thrusters for space propulsion and in other magnetized plasma environments relevant to materials processing and accelerator physics. Before joining Georgia Tech in 2023 and starting the Plasma Instrumentation and Engineering Research Lab, Dr. Tsikata was a researcher with the CNRS (National Center for Scientific Research) in France. She received graduate degrees from the Ecole Polytechnique in France, and a bachelor's degree from the Massachusetts Institute of Technology. Dr. Tsikata’s work has been recognized with awards from the American Institute of Aeronautics and Astronautics, CNRS, the French Physics Society, and the Electric Rocket Propulsion Society.