Relative Abundance and Escape Flux Composition During Storm Time: 3-D Model

The dynamic behavior of the "generalized" polar wind is investigated using a 3-D dynamic model. In this study, we simulate the behavior of a large number (~100 to 1000) of plasma-filled geomagnetic tubes. The model is composed of two components. The high-altitude component is based on a macroscopic particle-in-cell (mac-PIC) approach that extends from an altitude of 1200 km to several Earth radii. The lower boundary conditions of the mac-PIC model are provided by a 3-D fluid-like model (low-altitude component) that extends down to 100 km in altitude. The total number of simulation particles in the mac-PIC component is more than 10⁸. The generalized polar wind is followed for about 12 hours with a time step of 2.5 seconds. The model properly accounts for many physical mechanisms such as: ion-ion collisions, wave-particle interactions, magnetospheric enegetic electrons, and low-altitude ion energization. The computing-intensive nature of the model requires utilization of super computers with ~100 to 1000 processors. A 3-D picture is assembled from the temporal evolution of the individual flux tubes by keeping track of their locations. The resulting 3-D dynamic picture is investigated with special emphasis difference between the behaviors of the O⁺ and H⁺ ions. In particular, we address questions such as: (1) what is the relative abundance of the different ion species and (2) what is the composition of the ion escape flux, and how this varies with location and storm phase. These, and other results, are presented.