Modeling of Auroral Kilometric Radiation (AKR) Ordered Fine Structure via Electromagnetic and Electrostatic Ion Cyclotron (EMIC/EIC) Wave Stimulation and Particle Interaction

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The upward current region of the auroral acceleration region is an extremely dynamic region of electron and ion acceleration, wave-particle interaction, magnetospheric-ionospheric (M-I) coupling, and wave generation. In this region many different types of plasma waves are observed, including intense electrostatic and electromagnetic ion cyclotron (EIC/EMIC) waves. It is also the source region of auroral kilometric radiation (AKR), the most powerful terrestrial radio emission. Upward electric currents in this region are disrupted and modulated by EIC and EMIC waves, and thus provide a significant component of the M-I coupling dynamics. Frequency- vs. -time spectrograms of AKR reveal a narrow-banded fine structure that appears turbulent but displays specific features of frequency drift. Understanding the source of AKR fine structure is critical to understanding details of the wave generation mechanism, and the overall particle/wave energy balance. A new class of AKR fine structure referred to as ordered fine structure or striations has more recently been identified. The new data have suggests that AKR ordered fine structure results from stimulation by electromagnetic ion cyclotron (EMIC) and electrostatic ion cyclotron (EIC) waves. This project will use a 3-D particle-in-cell (PIC) plasma simulation code to study of the growth of EMIC/EIC waves in the auroral region and the stimulation of AKR ordered fine structure. The simulations determine how the morphology of the observed ordered fine structure depends on the frequency and wave length of the waves stimulating the AKR. The simulations will also contribute to developments in related fields of space and plasma science.