Observed Fluctuation Enhancement and Departure from WKB Theory in Sub-Alfvénic Solar Wind
Issued Date
2024-12-10
Resource Type
ISSN
20418205
eISSN
20418213
Scopus ID
2-s2.0-85211215966
Journal Title
Astrophysical Journal Letters
Volume
977
Issue
1
Rights Holder(s)
SCOPUS
Bibliographic Citation
Astrophysical Journal Letters Vol.977 No.1 (2024)
Suggested Citation
Ruffolo D., Thepthong P., Pongkitiwanichakul P., Roy S., Pecora F., Bandyopadhyay R., Chhiber R., Usmanov A.V., Stevens M., Badman S., Romeo O., Wang J., Goodwill J., Goldstein M.L., Matthaeus W.H. Observed Fluctuation Enhancement and Departure from WKB Theory in Sub-Alfvénic Solar Wind. Astrophysical Journal Letters Vol.977 No.1 (2024). doi:10.3847/2041-8213/ad9727 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/102383
Title
Observed Fluctuation Enhancement and Departure from WKB Theory in Sub-Alfvénic Solar Wind
Corresponding Author(s)
Other Contributor(s)
Abstract
Using Parker Solar Probe data from orbits 8 through 17, we examine fluctuation amplitudes throughout the critical region where the solar wind flow speed approaches and then exceeds the Alfvén wave speed, taking account of various exigencies of the plasma data. In contrast to WKB theory for noninteracting Alfvén waves streaming away from the Sun, the magnetic and kinetic fluctuation energies per unit volume are not monotonically decreasing. Instead, there is clear violation of conservation of standard WKB wave action, which is consistent with previous indications of strong in situ fluctuation energy input in the solar wind near the Alfvén critical region. This points to strong violations of WKB theory due to nonlinearity (turbulence) and major energy input near the critical region, which we interpret as likely due to driving by large-scale coronal shear flows.