Majority of Solar Wind Intervals Support Ion-Driven Instabilities
AffiliationUniv Arizona, Lunar & Planetary Lab
MetadataShow full item record
PublisherAmerican Physical Society
CitationKlein, K. G., Alterman, B. L., Stevens, M. L., Vech, D., & Kasper, J. C. (2018). Majority of Solar Wind Intervals Support Ion-Driven Instabilities. Physical review letters, 120(20), 205102, doi:https://doi.org/10.1103/PhysRevLett.120.205102
JournalPhysical Review Letters
Rights© 2018 American Physical Society
Collection InformationThis 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 firstname.lastname@example.org.
AbstractWe perform a statistical assessment of solar wind stability at 1 AU against ion sources of free energy using Nyquist’s instability criterion. In contrast to typically employed threshold models which consider a single free-energy source, this method includes the effects of proton and He2+ temperature anisotropy with respect to the background magnetic field as well as relative drifts between the proton core, proton beam, and He2+ components on stability. Of 309 randomly selected spectra from the Wind spacecraft, 53.7% are unstable when the ion components are modeled as drifting bi-Maxwellians; only 4.5% of the spectra are unstable to long-wavelength instabilities. A majority of the instabilities occur for spectra where a proton beam is resolved. Nearly all observed instabilities have growth rates γ slower than instrumental and ion-kinetic-scale timescales. Unstable spectra are associated with relatively large He2+ drift speeds and/or a departure of the core proton temperature from isotropy; other parametric dependencies of unstable spectra are also identified.
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