The Impact of Alfvénic Shear Flow on Magnetic Reconnection and Turbulence

Journal Article · Tue Oct 07 00:00:00 EDT 2025 · The Astrophysical Journal. Letters

DOI:https://doi.org/10.3847/2041-8213/ae0b56· OSTI ID:2998621

Ervin, Tamar ^[1]; Mallet, Alfred ^[1]; Eriksson, Stefan ^[2]; Swisdak, M. ^[3]; Juno, James ^[4]; Romeo, Orlando M. ^[1]; Phan, Tai ^[1]; Bowen, Trevor A. ^[1]; Livi, Roberto ^[1]; Whittlesey, Phyllis L. ^[1]; Larson, Davin E. ^[1]; Bale, Stuart D. ^[1]

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1. Univ. of California, Berkeley, CA (United States). Space Sciences Lab.
2. Univ. of Colorado, Boulder, CO (United States)
3. Univ. of Maryland, College Park, MD (United States)
4. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Magnetic reconnection is a fundamental and omnipresent energy conversion process in plasma physics. Novel observations of fields and particles from Parker Solar Probe (PSP) have shown the absence of reconnection in a large number of current sheets in the near-Sun solar wind. Using near-Sun observations from PSP encounters 4–11 (2020 January–2022 March), we investigate whether reconnection onset might be suppressed by velocity shear. We compare estimates of the tearing mode growth rate in the presence of shear flow for time periods identified as containing reconnecting current sheets versus nonreconnecting times, finding systematically larger growth rates for reconnection periods. Upon examination of the parameters associated with reconnection onset, we find that 85% of the reconnection events are embedded in slow, non-Alfvénic wind streams. We compare with fast, slow non-Alfvénic, and slow Alfvénic streams, finding that the growth rate is suppressed in highly Alfvénic fast and slow wind, and reconnection is not seen in these wind types, as would be expected from our theoretical expressions. These wind streams have strong Alfvénic flow shear, consistent with the idea of reconnection suppression by such flows. This could help explain the frequent absence of reconnection events in the highly Alfvénic, near-Sun solar wind observed by PSP. Finally, we find a steepening of both the trace and magnitude magnetic field spectra within reconnection periods in comparison to ambient wind. We tie this to the dynamics of relatively balanced turbulence within these reconnection periods and the potential generation of compressible fluctuations.

• Research Organization: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC02-09CH11466
• OSTI ID: 2998621
• Journal Information: The Astrophysical Journal. Letters, Journal Name: The Astrophysical Journal. Letters Journal Issue: 1 Vol. 992; ISSN 2041-8205; ISSN 2041-8213
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

slow solar wind
solar magnetic reconnection
solar wind