Periodic Structures in Solar Wind Composition Observed by the ACE/SWICS Instrument: Event Studies and Superposed Epoch Analysis
Abstract
Periodic structures in the solar wind plasma are extremely abundant within the ACE SWICS 12-minute-resolution composition data set. We have demonstrated this statistically in our 2020 AGU Fall Meeting poster [Gershkovich et al., 2020]. These structures, observed in-situ, are indicators of variations in composition at the Corona being imprinted onto the solar wind. Previous work showed that specific periodic structures in proton and alpha density exist at statistically significant levels and cannot be attributed to turbulence [Viall et al., 2009]. Prior to our work, only one periodic event had been identified in the ACE SWICS composition data [Kepko et al., 2016]. We are greatly expanding upon knowledge in this area by analyzing 13 years (1998-2011) of SWICS 12-minute composition data, looking at all ions and charge states of sufficiently high data quality. Composition is excellent for studying processes occurring at the Sun as it is frozen into the solar wind and has no means to evolve as the plasma advects from the solar atmosphere towards the point of observation. Here, we present the results of a superposed epoch analysis consisting of several events and examine trends in charge-state, mass and First Ionization Potential (FIP) in the 24-hour windows before, during and after each event. We compare the composition ratio and charge state data to previously established typical coronal hole and streamer values and discuss the patterns that emerge.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH25F2157G