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Inherent length scales of periodic mesoscale density structures in the solar wind over two solar cycles
  • Larry Kepko,
  • Nicholeen Mary Viall,
  • Kathryn Wolfinger
Larry Kepko
NASA Goddard Space Flight Center, NASA Goddard Space Flight Center

Corresponding Author:larry.kepko@nasa.gov

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Nicholeen Mary Viall
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Kathryn Wolfinger
University Colorado, Boulder, University Colorado, Boulder
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It is now well-established through multiple event and statistical studies that the solar wind at 1 AU contains contains periodic, mesoscale (L~100-1000 Mm) structures in the proton density. Composition variations observed at 1 AU within periodic density structures and remote sensing observations of similar structures in the young solar wind indicate that at least some of these periodic structures originate in the solar atmosphere as a part of solar wind formation. Viall [2008] analyzed 11 years of data from the Wind spacecraft near L1 and demonstrated a recurrence to the length scales of periodic structures in the solar wind proton density observed, and a potential solar cycle dependence. In the time since that study, Wind has collected 14 additional years of solar wind data, allowing a more thorough examination of the dependence of these structures as a function of solar cycle. In addition, the Wind plasma data have been reprocessed in the interim, and new methods for spectral background approximation have been developed, allowing a reevaluation of the precision and accuracy of the initial study. In this study, we analyze 25 years of Wind data collected near L1, and produce occurrence distributions of statistically significant periodic length scales in proton density. The results confirm the Viall [2008] study and significantly extend those results to show a solar cycle dependence of the length scales, and a possible relation to solar “termination” events.
Aug 2020Published in Journal of Geophysical Research: Space Physics volume 125 issue 8. 10.1029/2020JA028037