2:00 PM - 2:15 PM
[PEM15-12] Nonlinear Evolution of Density Structure in IAR Using 2D Multi-Fluid Plasma Simulation
Keywords:IAR, aurora, Alfvén wave
IARs (Ionospheric Alfven Resonators) are regions of Alfven wave resonance located above the ionosphere and have major impacts on auroral activities in the Magnetosphere-Ionosphere coupling system. From EISCAT radar and FAST satellite observations, previous research found low plasma density regions and signatures of dispersive Alfven waves and accompanying particle accelerations within IARs structures [Aikio et al., 2004, Chaston et al., 2006]. These observed particle accelerations could be a potential energy source for the initial formation and evolution process of auroral acceleration regions which remain an unsolved problem. Therefore, it is necessary to elucidate the mechanism of plasma density depletions and filamentations for dispersive Alfven wave. In previous numerical studies [Streltsov and Lotko 2008, Sydorenko et al., 2008], they focused on the density depletion and considered that the parallel nonlinear Lorentz forces originated from IARs resonant structures are one of the factors. Based on this idea, they simulated the evolution of density structures using multi-fluid plasma simulation and confirmed low density region formation at the nodes of resonant structure. However, the density enhanced regions are simultaneously formed at the antinodes which does not match observational characteristics.
Given this contradiction between observations and models, we proposed that not only parallel nonlinear Lorentz forces arisen from IAR resonant structures, but also perpendicular nonlinear Lorentz forces arisen from the perpendicular scales of incident Alfven wave from the magnetosphere are important for plasma density decreases. According to this idea, we conduct numerical experiments by multi-fluid plasma model to simulate the plasma density variations while incorporating nonlinear forces in both directions and reproduce dispersive Alfven waves in IARs. In our presentation, we will discuss the importance of IARs for auroral accelerations formation processes and compare our simulation results of nonlinear density structure evolutions with observational facts.
Given this contradiction between observations and models, we proposed that not only parallel nonlinear Lorentz forces arisen from IAR resonant structures, but also perpendicular nonlinear Lorentz forces arisen from the perpendicular scales of incident Alfven wave from the magnetosphere are important for plasma density decreases. According to this idea, we conduct numerical experiments by multi-fluid plasma model to simulate the plasma density variations while incorporating nonlinear forces in both directions and reproduce dispersive Alfven waves in IARs. In our presentation, we will discuss the importance of IARs for auroral accelerations formation processes and compare our simulation results of nonlinear density structure evolutions with observational facts.