Inherent Spatial Scales of Solar Wind Periodic Structures Found in ACE/SWICS Data

The existence of prevalent, statistically significant, periodic structures in the in-situ observations of number density and solar wind composition at 1 AU can meaningfully address outstanding questions about solar wind formation and evolution. Past work [ Viall et al., 2009] has revealed that specific periodicities in solar wind proton and alpha density, as well as dayside magnetospheric oscillations, exist and suggest that mechanisms beyond what can be attributed to turbulence are responsible. Composition is frozen into the solar wind and does not evolve as the plasma advects from the upper atmosphere of the Sun, making it invaluable to studying the processes that form the heliosphere. Although a periodic event has been identified in the ACE SWICS data previously [ Kepko et al., 2016], we greatly expand upon the scope of all prior work by analyzing 13 years (1998-2011) of SWICS 12-minute solar wind composition data, considering all ion species and charge states with sufficient data quality. We now have a database of validated windows, for a variety of ion species and charge states, which have sufficient continuity, counts and low enough errors to be suitable for any time series analysis. Spectral peaks identified by our algorithm are required to pass both an amplitude and a harmonic F-test at a 90% or greater confidence level. This ensures that rigorous statistical significance criteria have been met. We are conducting an unprecedented study of the relationships between the periodicities of different ion densities and their dependence on First Ionization Potential (FIP) bias, charge state, and mass. Here, we present statistical results that identify generally prevalent periodic enhancements as well as event studies that explore the spectral behaviors associated with heliospheric current sheet crossings, ICME sheaths and stream interaction regions. This analysis of composition variations informs our understanding of solar wind formation and evolution.