In Situ Mechanisms are Necessary for Switchback Formation

Magnetic switchbacks are reversals (deflection angle θ B > 90°) in the radial magnetic field B r , accompanied by proton bulk flow v p enhancement. The switchback generation mechanism(s) is still debated, though switchback evolution is linked to coronal heating. In this study, we provide an exhau...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2024-08, Vol.970 (2), p.L26
Main Authors: Akhavan-Tafti, M., Soni, S. L.
Format: Article
Language:English
Subjects:
Alfven waves
Corona
Coronal heating
Evolution
Fluctuations
Magnetic fields
Magnetic variations
Solar corona
Solar probes
Solar wind
Solar wind flow
Wind flow
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Summary:Magnetic switchbacks are reversals (deflection angle θ B > 90°) in the radial magnetic field B r , accompanied by proton bulk flow v p enhancement. The switchback generation mechanism(s) is still debated, though switchback evolution is linked to coronal heating. In this study, we provide an exhaustive investigation of magnetic fluctuations in the first 14 Parker Solar Probe encounters. Our results show (1) enhanced magnetic fluctuations ( θ B ≤ 90°) and (2) clear absence of B r reversals θ B > 90° in sub-Alfvénic solar corona. It is concluded that switchbacks are either generated locally in super-Alfvénic solar wind (in situ) or that a subpopulation of magnetic fluctuations generated in sub-Alfvénic solar corona (ex situ) evolves into switchbacks once in super-Alfvénic solar wind flow. In other words, in situ mechanisms are necessary for switchback formation. It is then hypothesized that interchange reconnection in sub-Alfvénic solar corona can provide both the necessary ex situ trigger and in situ evolution mechanisms for switchback formation, though other trigger mechanisms cannot be ruled out.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ad60bc