Joint Physics Dept. Seminar

April 12, Friday (** SPECIAL DAY**)

Recent Progress Made in Ionospheric E-Region Turbulence Research

Dr. Jean-Pierre St.-Maurice

Univ. of Saskatchewan, Canada

(Terrestrial Phys., Host: Perry)

*Room: FMH 408 (** SPECIAL ROOM **)

*Time: 10:15 am - 11:15 am with 10 am teatime (**SPECIAL TIME**)

*Webex site for those who cannot attend in-person:

https://njit.webex.com/meet/gperry

(APPROVAL by Prof Ahn REQUIRED for APPH/MTSE PhD students to attend online)

Intense lower ionospheric Hall currents triggered by auroral electric fields introduce meter-size turbulence through a modified two-stream instability called the Farley-Buneman instability. For several decades, this turbulence has been studied experimentally with ground-based radars and through numerous rocket flights. This being stated, the recent introduction of simultaneous high resolution images of the aurora and of multiple interferometry links with coherent radars with high gain and sensitivity has opened new windows on the phenomenon. Theoretical insights from numerical simulations and analytical work have been keeping reasonable pace with the observations. With this in mind, my presentation will focus on the physical insights gained from the new observations and the ideas that they have inspired. After a brief overview of the basic destabilizing mechanism, I will start with a discussion of the unexpected properties of the phase velocities observed with radars and what they mean. I will follow this with modern studies of the connection between the location of radar echoes from the aurora and the location of the aurora itself and a discussion of what their link implies. I will continue with a discussion of the at-first-sight-unexpected difference between the velocities retrieved from the Doppler shifts associated with turbulent structures and the velocities obtained from the motion of the turbulent targets. I plan to end with a brief discussion of the energy and electric current dissipation associated with the turbulent structures.