Flux rope merging and the structure of switchbacks in the solar wind

Abstract

A major discovery of Parker Solar Probe (PSP) was the presence of large numbers of localized increases in the radial solar wind speed and associated sharp deflections of the magnetic field - switchbacks (SB). A possible generation mechanism of SBs is through magnetic reconnection between open and closed magnetic flux near the solar surface, termed interchange reconnection that leads to the ejection of flux ropes (FR) into the solar wind. Observations also suggest that SBs undergo merging, consistent with a FR picture of these structures. The role of FRs merging in controlling the structure of SB in the solar wind is explored through direct observations, through analytic analysis, and numerical simulations. Analytic analysis reveals key features of the structure of FR and their scaling with the heliocentric distance R that are consistent with observations and that reveal the critical role of merging in controlling the SB structure. FR merging is shown to be energetically favorable to reduce the strength of the wrapping magnetic field and drive the observed elongation of SBs. A further consequence is the resulting dominance of the axial magnetic field within SBs that leads to the characteristic sharp rotation of the magnetic field into the axial direction at the SB boundary that is revealed in observations. Finally, the radial scaling of the SB area in the FR model of SBs suggests that the observational probability of SB identification should be insensitive to R, which is consistent with the most recent statistical analysis of SB observations from PSP.

21 pages, 9 figures

References in corpus (12)

• Switchbacks in the near-Sun magnetic field: long memory and impact on the turbulence cascade
• The Solar Probe Cup on Parker Solar Probe
• Magnetic field kinks and folds in the solar wind
• Parker Solar Probe In-Situ Observations of Magnetic Reconnection Exhausts During Encounter 1
• Switchbacks Explained: Super-Parker Fields -- the Other Side of the Sub-Parker Spiral
• Coronal-Jet-Producing Minifilament Eruptions as a Possible Source of Parker Solar Probe (PSP) Switchbacks
• Identification of Magnetic Flux Ropes from Parker Solar Probe Observations during the First Encounter
• The Enhancement of Proton Stochastic Heating in the near-Sun Solar Wind
• Direct evidence for magnetic reconnection at the boundaries of magnetic switchbacks with Parker Solar Probe
• On the origin of switchbacks observed in the solar wind
• Small-scale Magnetic Flux Ropes with Field-aligned Flows via the PSP In-situ Observations
• Evolving Solar Wind Flow Properties of Magnetic Inversions Observed by Helios

Cited by in corpus (10)

• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• Magnetic Reconnection as the Driver of the Solar Wind
• Whistler Wave Observations by \textit{Parker Solar Probe} During Encounter $1$: Counter-Propagating Whistlers Collocated with Magnetic Field Inhomogeneities and their Application to Electric Field Measurement Calibration
• Whistler waves generated inside magnetic dips in the young solar wind: observations of the Search-Coil Magnetometer on board Parker Solar Probe
• Oscillatory reconnection and waves driven by merging magnetic flux ropes in solar flares
• Solar Chromospheric Network as a Source for Solar Wind Switchbacks
• Quantifying the diffusion of suprathermal electrons by whistler waves between 0.2 and 1 AU with Solar Orbiter and Parker Solar Probe
• Reconstruction of Polarization Properties of Whistler Waves From Two Magnetic and Two Electric Field Components: Application to Parker Solar Probe Measurements
• The effects of resistivity on oscillatory reconnection and consequences for solar flare Quasi Periodic Pulsations
• Switchbacks near Boundaries of Small-scale Magnetic Flux Ropes in the Young Solar Wind from Parker Solar Probe Observations