11:00 AM - 11:15 AM
[PEM09-22] Ion accelerations due to two approaching flow fronts: Application to high-energy ion production in the magnetotail
Keywords:magnetotail, high-energy ion, substorm
By performing spatially 1-D (2-D in velocity) test particle simulations where we assumed a couple of approaching ExB-drift flows, we have confirmed the production of high-energy ions as well as the change of the energy spectrum of ions associated with the acceleration. The simulation result shows that such high-energy ions are produced with scale length shorter than the magnetotail diameter. Furthermore, we find that the maximum energy of the accelerated ions depends on the distance of the two flow fronts and the dawn-dusk scale lengths of the flows. If the dawn-dusk scale length is infinite, the energy spectrum of accelerated ions is well fitted by the analytically calculated spectrum. Our simulation results and analytical calculation indicate that the distance and dawn-dusk scale length of two flow fronts can be estimated from the observations of electromagnetic field and flow speed, the maximum ion energy and the change of the energy spectrum of ions in the magnetotail, where such two approaching flow fronts commonly exist.