During its trajectory, Wind spent a significant amount of time in the magnetotail, where its SupraThermal Ion Composition Spectrometer (STICS) measured the mass and mass per charge of protons, alpha particles, and heavy ions with an energy/charge ratio up to 226 keV/e. Although STICS originally aimed to measure the abundance of these ion species in the solar wind, its measurements within the magnetosphere from 1995 to 2002 help us identify preferential entry between the different solar wind ion species. This study statistically analyzes how the ratio between solar wind heavy ions and alpha particles (Heavies Solar Wind / He2+) varies for different upstream conditions and locations within the magnetosphere: northward vs. southward Interplanetary Magnetic Field (IMF), low vs. high solar wind density (Nsw), low vs. high solar wind dynamic pressure (PDyn), slow vs. fast solar wind (Vsw), and dawn vs. dusk. Our results indicate that the HeaviesSolar Wind enter the magnetosphere more efficiently than He2+ during northward IMF and that the Heavies Solar Wind / He2+ ratios decrease during high PDyn. In addition, the Heavies Solar Wind / He2+ ratios exhibit a dawn-dusk asymmetry, highly skewed towards the dawn side for all upstream cases likely due to charge-exchange processes.
Colón-Rodríguez, S., Liemohn, M. W., Raines, J. M, & Lepri, S.T. (2024). Solar wind heavy ions and alpha particles within Earth’s magnetosphere and their variability with upstream conditions. Journal of Geophysical Research Space Physics. In preparation.
