Farley-Buneman instabilities in the auroral region: Continuous hybrid simulations and empirical modeling
MetadataShow full item record
Rojas Villalba, Enrique Luis Alfonso
The coupling between the magnetosphere and the high latitude ionosphere through energetic particles and electromagnetic fields results in the production of Hall currents that drive Farley-Buneman instabilities. Numerous studies have shown that these irregularities can modify the mean state of the ionosphere through wave heating, and therefore, change the local temperature, plasma density, composition, and conductivity. Linear, local fluid theory of Farley-Buneman instabilities, although limited, has produced some important, verified predictions. Nevertheless, linear theory falls short in explaining several features observed in the experimental data. Particle in cell (PIC) simulations have been so far the most successful approach for this purpose, and have been able to resolve most of the small scale nonlinear features of Farley--Buneman instabilities as seen by radars and rockets. Furthermore, a heuristic model consistent with PIC results was built to predict temperature enhancements seen with incoherent scatter radars and to interpret plasma state parameters from Doppler data obtained from coherent backscatter radars. However, recent satellite and radar measurements have challenged this heuristic model. Moreover, these discrepancies are related to non-local scale processes, which current state of the art PIC implementations cannot address because of the extreme computational cost. In order to address these discrepancies, information about the large scale spectral features of these instabilities as well as the local plasma state parameters have to be coupled by physical models. Given the computational limitations of PIC simulations, more scalable methods are needed. Furthermore, it is fundamental to find new ways to assess the proposed heuristic model. Finally, new approaches need to be explored beyond reductionist models, which are often constrained by computational limitations. In this work, we used a non-reductionist model to explain one of the most important non-linear features of Farley-Buneman instabilities, the evolution of the phase speeds of the different wave modes, by using the formalism of stochastic differential equations. Moreover, we used the electrostatic nature of the convection electric field to assess the physical consistency of the heuristic model mentioned above: the model will be satisfactory to the extent that the plasma flows derived from it are incompressible. Finally, we implemented a continuous hybrid simulation of Farley-Buneman instabilities. We showed that the proposed numerical algorithm is significantly more scalable than PIC implementations and that it can reproduce most of the physical behavior of these instabilities.
Inverse Methods; Plasma Instabilities; Plasma Simulations; Space Physics; Stochastic
Hysell, David L.
Bindel, David; Seyler, Charles
Ph. D., Atmospheric Science
Doctor of Philosophy
dissertation or thesis