The ionosphere — Earth’s partially ionized upper atmosphere from roughly 80 to 1000 km — is shaped by a rich interplay of electromagnetic forcing, collisional chemistry, and plasma instabilities. It is simultaneously a practical medium for communications, GPS, and over-the-horizon radar, and an extraordinary natural plasma physics laboratory. When electric fields accelerate electrons across magnetic field lines in the E region (90–150 km), the resulting current-driven instabilities generate plasma turbulence that has fascinated and challenged theorists since the 1960s.
Our group attacks these problems from multiple directions. We run massively parallel particle-in-cell (PIC), hybrid, and multi-fluid simulations that resolve kinetic physics inaccessible to fluid models. Senior Research Scientist Yakov Dimant leads much of the analytic theory in the group, providing essential physical insight alongside the simulations. We compare our results directly to data from incoherent scatter radar (ISR) systems including Millstone Hill, PFISR, and the Jicamarca Observatory.
We recently completed the first fully kinetic 3D simulations of the high-latitude electrojet spanning an entire turbulent flux tube from the E region through the F region — a landmark computation that was previously out of reach. These simulations reveal how turbulence couples across altitudes and modifies global magnetosphere–ionosphere dynamics (Oppenheim, Dimant, Koontaweepunya, Green, Evans, GRL 2025).
In the equatorial and high-latitude E region, strong convective electric fields drive the Farley–Buneman (FB) instability, producing field-aligned density irregularities and powerful coherent radar echoes. The nonlinear saturation and anomalous heating produced by FB turbulence remain active research questions. Our PIC and hybrid simulations directly resolve the kinetic wave–particle dynamics that determine the turbulent spectrum and electron temperature enhancement, with direct implications for ionospheric conductivities and global storm dynamics.
Small-scale electrojet turbulence alters the macroscopic conductivity of the ionosphere, which in turn affects the global magnetosphere–ionosphere-thermosphere (MIT) system. We have shown that turbulence-induced anomalous conductivities influence how energy flows during geomagnetic storms and substorms. Our work has been incorporated into global MIT models such as TIEGCM and LFM, directly connecting our microphysics results to space weather prediction.
Coherent radar echoes appearing near 150 km altitude in the daytime equatorial ionosphere have puzzled researchers for decades — they occur at altitudes where standard instability theory predicts no turbulence. In a 2016 GRL paper highlighted in Science magazine, we proposed and simulated a new mechanism: photoelectron-driven upper hybrid waves. Subsequent work by Longley et al. (2020) and Green et al. (2023) has refined and extended this theory, making the 150 km echo problem one of our group’s most cited contributions.
Sub-auroral ion drifts (SAID) and the recently discovered STEVE (Strong Thermal Emission Velocity Enhancement) optical phenomenon are shaped by sub-auroral electric fields and E-region plasma turbulence. Our group contributed 3D simulations of SAID flow channels and analyzed how E-region turbulence affects their formation and evolution, in collaboration with groups at Virginia Tech, BU Astronomy, and Boston University Space Physics (Peña et al. 2024, 2025).
In the F region (150–1000 km), density gradients combined with convective drifts seed the gradient-drift instability, producing irregularities that scatter GPS signals and disrupt communications. Our kinetic simulations probe how equatorial spread-F irregularities develop from kilometer to meter scales, filling in the gap between fluid-scale models and radio-wave scintillation observations. An active NSF-funded project simulates electrojet instabilities over the full range from the equatorial E region to low-mid latitude boundaries.
Incoherent scatter radar spectral measurements reveal electron and ion temperatures and drift velocities with great precision — but only if the spectral theory is correct. Our group has developed PIC-based simulations of ISR spectra that include electron–ion Coulomb collisions, electron-electron collisions, and beam–plasma effects. These simulations expose systematic biases in standard ISR temperature retrievals and improve the accuracy of ionospheric diagnostics worldwide.
Ionospheric physics connects fundamental plasma physics to space weather, GPS accuracy, and global climate — a field with both deep scientific questions and practical relevance. Students in this program develop skills in kinetic simulation, radar data analysis, and plasma theory that are valued in academia, national labs, and the aerospace industry.
Learn more about the BU Astronomy PhD program at bu.edu/astronomy/graduate or contact Prof. Oppenheim at meerso@bu.edu.