Physics Dept. Seminar

January 30, Monday

Ionospheric flow channels from different perspectives

Joaquín Díaz Peña

Boston Univ.

(Terrestrial Physics, Host: Goodwin)

Room: ECE 202

Time: 11:45 am - 12:45 pm with 11:30 am teatime

Mesoscale plasma flow channels (100km – 500km) arise in the high-latitude ionosphere under various conditions. These flow channels have structural effects on the surrounding convecting plasma and the dynamics of the coupled atmosphere-ionosphere-magnetosphere system, which are not well understood. There are several ways to study such flow channels and their interactions. In the first case study, we can take a purely observational approach, exploiting the volumetric sampling capabilities of the Resolute Bay Incoherent Scatter Radar (RISR-N) in collaboration with all-sky imagery and in-situ measurements from space missions. This was done to examine the interplay between cold plasma transport and auroral precipitation during a high-latitude lobe reconnection event on the dawn side. The combined effects of transport and magnetic stress release associated with a high-latitude reconnection pulse drove a co-mingling between patches and soft electron precipitation, creating common regions of elevated electron density and temperature. This first case study suggests a new mechanism for creating a “hot patch," highlighting the need for densely distributed observations in space and time to understand mesoscale and small-scale ionospheric dynamics in regions subject to complex forcing.

On the other hand, advanced technology allows us to run complicated models with a commercial laptop, so we can study different flow channels by modeling them. Especially channels outside the usual ground-based network of sensors, like the STEVE auroral phenomenon. The coupling between electrodynamics and transport in flow channels is often modeled in a two-dimensional sense, with the collisional E-region treated as a passive medium for the closure of magnetospheric currents. But a realistic model that includes extreme events, like STEVE, must consider the interplay between field-aligned currents, ion closure currents, ion and electron transport, dynamic ion composition changes, and optical excitations, calling for a hybrid modeling scheme that embodies both transport and kinetic effects of the channel. This second case study, my current work, tries to integrate the three-dimensional GEMINI transport model with the one-dimensional GLOW flux-tube model with turbulence effects due to the Farley-Buneman kinetic instability. The GEMINI model solves the electron and ion fluid equations in three dimensions, along with Maxwell’s equations, to determine the resulting quasi-static electric field structure. The GLOW model solves the field-aligned two-stream Boltzmann electron transport equations, accounting for chemical processes and optical excitation within the ionosphere-thermosphere system, including superthermal electron effects. The coupled model remains an incomplete representation of the kinetic effects in the channel, only including abnormal electron heating and nonlinear currents, but begins to enable a more realistic representation of magnetosphere-ionosphere coupling in mesoscale flow channels.