[PEM16-P14] Excitation mechanism of storm-time Pc5 ULF waves by ring current ions
Keywords:ring current, magnetic storm, Pc5 ULF, drift-bounce resonance, drift-kinetic simulation
In order to simulate the excitation mechanism of the storm-time Pc5 waves, we perform a kinetic simulation for ring current particles using GEMSIS-RC model (Amano et al., 2011), in which five-dimensional drift-kinetic equation for PSD of ring current ions and Maxwell equation are solved self-consistently, and the first adiabatic invariant is assumed to be conserved. In order to simplify injection model, we set a localized high pressure region around midnight consisting of O+ ions which have a Maxwellian velocity distribution of the temperature 16 keV (O+ ion) with a loss cone. In addition, the presence of a background cold dense plasma, which is fixed to the initial condition is assumed. The fixed boundary condition for the field quantities is used, and the mirror reflection at the ionosphere is assumed at the inner boundary.
We investigate the power spectrum of magnetic field fluctuations, and it is shown that primarily poloidal mode (Br) is excited from duskside to afternoon magnetic local times. The frequency of the excited waves matches the expectation from the drift-bounce resonance conditions for the locally dominant O+ ions estimated from the simulated PSD. It is also found that poloidal mode wave propagates westward from 1800 to 1200 MLT associated with the westward transport of O+ ions. We also investigate the local PSD distribution, and the systematic modulation of the ion pitch angle distribution associated with the phase of excited waves are confirmed. Detailed correspondence of the PSD distributions and the wave properties will be also performed.
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