Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends
Name:
Martinović_2021_ApJ_923_116.pdf
Size:
1.364Mb
Format:
PDF
Description:
Final Published Version
Publisher
IOP Publishing LtdCitation
Martinović, M. M., Klein, K. G., Ďurovcová, T., & Alterman, B. L. (2021). Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends. Astrophysical Journal.Journal
Astrophysical JournalRights
Copyright © 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
Instabilities described by linear theory characterize an important form of wave-particle interaction in the solar wind. We diagnose unstable behavior of solar wind plasma between 0.3 and 1 au via the Nyquist criterion, applying it to fits of ∼1.5M proton and α particle Velocity Distribution Functions (VDFs) observed by Helios I and II. The variation of the fraction of unstable intervals with radial distance from the Sun is linear, signaling a gradual decline in the activity of unstable modes. When calculated as functions of the solar wind velocity and Coulomb number, we obtain more extreme, exponential trends in the regions where collisions appear to have a notable influence on the VDF. Instability growth rates demonstrate similar behavior, and significantly decrease with Coulomb number. We find that for a nonnegligible fraction of observations, the proton beam or secondary component might not be detected, due to instrument resolution limitations, and demonstrate that the impact of this issue does not affect the main conclusions of this work. © 2021. The Author(s). Published by the American Astronomical Society.Note
Open access articleISSN
0004-637XVersion
Final published versionae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/ac3081
Scopus Count
Collections
Except where otherwise noted, this item's license is described as Copyright © 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.