Simulation of Cold Ion Transport Originating From the SED Plume Into Dayside Magnetosphere

In this study, based on the Dynamic-Kinetic Fluid (DyFK) model, we conduct simulations on the field-aligned transport of cold ions (<1 eV) within three independent closed flux tubes from different starting points (L = 3.0 Re, L = 3.122 Re and L = 3.5 Re, respectively) during the 2015 St. Patrick's Day storm. These flux tubes magnetically connect the plasmaspheric plume with the ionospheric Storm Enhanced Density (SED) plume but drift toward the dayside magnetopause under ExB effects. Meanwhile, we can obtain the density variations of three ions species (H+, O+, and He+, respectively) around the flux tubes' apex (at the magnetic equator) as a function of the L shell. The simulations present the temporal evolution of cold plasma along these drifting flux tubes. We found that with increasing initial L shell location of the flux tube, there are more ionospheric cold light ions (H+ and He+) flowing into the equatorial region while the inflows of cold heavy ions (O+) toward the equator decrease. As the simulated flux tube drifts toward dayside magnetopause from the main plasmasphere (L = 3.0 Re), the SED sourced heavy ions pile up near the magnetic equator at low L shells (L Re) due to gravitational effects, while the light ions rapidly reach density equilibrium along the flux tube. With the flux tube drifting beyond L > 4.0 Re, the piled-up cold heavy ions will later transport into the magnetic equatorial region and furnish the dayside magnetosphere, demonstrating that the SED is another supplier of magnetospheric cold heavy ions (O+).