Subventions et des contributions :

Subvention ou bourse octroyée s'appliquant à plus d'un exercice financier. (2017-2018 à 2022-2023)

After several decades of studies our basic understanding of the ionosphere now rests on solid foundations. Nevertheless, with the constant progress in instrumental capabilities some old topics need to be revisited, not to mention that the new datasets can often reveal interesting surprises, which present new challenges. The basic reason for this state of affair is that the ionospheric plasma and the upper atmosphere/thermosphere are made of rarefied gases and often subject to strong departures from equilibrium, be it through electric field and currents, or large spatial variations in electric fields, temperatures or densities. This produces turbulence more often than not, the origin and evolution of which both need to be understood if the transport of particles momentum and energy through the system is to be properly quantified. I use observations from advanced radar systems, rockets and satellites to query the medium. From this starting point I carefully study the generation of electrical currents, the heating of both the neutral atmosphere and the ionosphere and their consequences through the generation of bulk motions and instabilities, particularly in the plasma component. My long term objective is to gain a deep understanding of the processes associated with these large departures from equilibrium. This is a challenging goal, as many of the phenomena are unpredictable (there are lots of feedback and nonlinear mechanisms involved). Specific short term objectives to be pursued with my students and collaborators are: (1) a renewed study of ion velocity distributions under large Mach number conditions. This subject is due for renewed scrutiny in view of modern radar and satellite data; (2) new linear and nonlinear theories of plasma instabilities in the lower ionosphere and in the upper mesosphere, using new insights from recent datasets; (3) using new radar systems deep in the Canadian polar cap, and Canadian satellite projects to produce a careful investigation of the plasma cusp in the ionosphere, which is the footprint of the region where the solar wind plasma becomes connected with the earth plasma. The origin of atmospheric heating in that region and the response are not well understood; (4) investigating the various responses of the high latitudes to solar wind input. This includes the production and propagation of so-called patches of ionization in the upper atmosphere, and the degree to which magnetic substorms and storms are triggered by changes in the solar wind magnetic field and dynamic pressure; (5) investigating the electrodynamics of low latitude regions both in relation to large solar wind perturbations and for much quieter conditions, which adds an interesting perspective on the whole ionosphere; (6) the study HF radio wave propagation under various conditions will also be scrutinized in order to better locate HF radar echoes, and monitor large scale ionospheric structures.