A solar source of Alfvénic magnetic field switchbacks: {\em in situ} remnants of magnetic funnels on supergranulation scales

Abstract

One of the striking observations from the Parker Solar Probe (PSP) spacecraft is the prevalence in the inner heliosphere of large amplitude, Alfvénic magnetic field reversals termed 'switchbacks'. These $\delta B_R/B\sim \mathcal{O}(1$) fluctuations occur on a range of timescales and in {\em patches} separated by intervals of quiet, radial magnetic field. We use measurements from PSP to demonstrate that patches of switchbacks are localized within the extensions of plasma structures originating at the base of the corona. These structures are characterized by an increase in alpha particle abundance, Mach number, plasma $\beta$ and pressure, and by depletions in the magnetic field magnitude and electron temperature. These intervals are in pressure-balance, implying stationary spatial structure, and the field depressions are consistent with overexpanded flux tubes. The structures are asymmetric in Carrington longitude with a steeper leading edge and a small ($\sim$1${}^{\circ }$) edge of hotter plasma and enhanced magnetic field fluctuations. Some structures contain suprathermal ions to $\sim$85 keV that we argue are the energetic tail of the solar wind alpha population. The structures are separated in longitude by angular scales associated with supergranulation. This suggests that these switchbacks originate near the leading edge of the diverging magnetic field funnels associated with the network magnetic field - the primary wind sources. We propose an origin of the magnetic field switchbacks, hot plasma and suprathermals, alpha particles in interchange reconnection events just above the solar transition region and our measurements represent the extended regions of a turbulent outflow exhaust.

18 pages, 9 figures, submitted to Astrophys. J

References in corpus (16)

• Solar Coronal Jets: Observations, Theory, and Modeling
• Switchbacks in the near-Sun magnetic field: long memory and impact on the turbulence cascade
• On the generation of solar spicules and Alfvénic waves
• The Magnetic Field in the Solar Atmosphere
• In-situ switchback formation in the expanding solar wind
• Magnetic connectivity of the ecliptic plane within 0.5 AU : PFSS modeling of the first PSP encounter
• Electrons in the Young Solar Wind: First Results from the Parker Solar Probe
• Ion Scale Electromagnetic Waves in the Inner Heliosphere
• Parker Solar Probe observations of proton beams simultaneous with ion-scale waves
• Switchbacks Explained: Super-Parker Fields -- the Other Side of the Sub-Parker Spiral
• Evidence for polar jets as precursors of polar plume formation
• A zone of preferential ion heating extends tens of solar radii from Sun
• Hi-C 2.1 Observations of Jetlet-like Events at Edges of Solar Magnetic Network Lane
• Plumelets: Dynamic Filamentary Structures in Solar Coronal Plumes
• Could switchbacks originate in the lower solar atmosphere? I. Formation mechanisms of switchbacks
• Could switchbacks originate in the lower solar atmosphere? II. Propagation of switchbacks in the solar corona

Cited by in corpus (45)

• Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum
• Magnetic Reconnection as the Driver of the Solar Wind
• Interchange reconnection as the source of the fast solar wind within coronal holes
• In situ observations of large amplitude Alfvén waves heating and accelerating the solar wind
• Quasiperiodic Energy Release and Jets at the Base of Solar Coronal Plumes
• Observation of Magnetic Switchback in the Solar Corona
• Patches of magnetic switchbacks and their origins
• New Evidence on the Origin of Solar Wind Microstreams/Switchbacks
• Stirring the Base of the Solar Wind: On Heat Transfer and Vortex Formation
• Direct observations of a complex coronal web driving highly structured slow solar wind
• Statistical analysis of intermittency and its association with proton heating in the near Sun environment
• The Structure and Origin of Switchbacks: Parker Solar Probe Observations
• On the Generation and Evolution of Switchbacks and the Morphology of Alfvénic Transition: Low Mach-number Boundary Layers
• The impact of multi-fluid effects in the solar chromosphere on the ponderomotive force under LTE and NEQ ionization conditions
• The preferential orientation of magnetic switchbacks, implications for solar magnetic flux transport
• Helios 2 observations of solar wind turbulence decay in the inner heliosphere
• Suprathermal Ion Energy spectra and Anisotropies near the Heliospheric Current Sheet crossing observed by the Parker Solar Probe during Encounter 7
• On the properties of Alfvénic switchbacks in the expanding solar wind: the influence of the Parker spiral
• On the formation of solar wind & switchbacks, and quiet Sun heating
• Parker Solar Probe Observations of High Plasma Beta Solar Wind from Streamer Belt
• Coronal hole picoflare jets are progenitors of both fast and Alfvénic slow solar wind
• Multi-Fluid Simulations of Upper Chromospheric Magnetic Reconnection with Helium-Hydrogen mixture
• Multi-stage reconnection powering a solar coronal jet
• Density And Velocity Fluctuations of Alpha Particles in Magnetic Switchbacks
• Coronal Heating and Solar Wind Generation by Flux Cancellation Reconnection
• Statistical Evidence for Small-Scale Interchange Reconnection at a Coronal Hole Boundary
• Thermal energy budget of electrons in the inner heliosphere: Parker Solar Probe Observations
• Solar Spicules, Filigrees and Solar Wind Switchbacks
• Are Switchback boundaries observed by Parker Solar Probe closed?
• Cross Helicity and the Helium Abundance as an in situ Metric of Solar Wind Acceleration
• The Temperature, Electron, and Pressure Characteristics of Switchbacks: Parker Solar Probe Observations
• Solar Chromospheric Network as a Source for Solar Wind Switchbacks
• Switchback Deflections Beyond the Early Parker Solar Probe Encounters
• Tracing magnetic switchbacks to their source: An assessment of solar coronal jets as switchback precursors
• Thin coronal jets and plasmoid-mediated reconnection: Insights from Solar Orbiter observations and Bifrost simulations
• Dominance of 2-Minute Oscillations near the Alfvén Surface
• Energetic particle dynamics in a simplified model of a solar wind magnetic switchback
• Role of magnetic arcades in explaining the puzzle of the gamma-ray emission from the solar disk
• Solar Wind Structures from the Gaussianity of Magnetic Magnitude
• Formation of Magnetic Switchbacks via expanding Alfvén Waves
• Switchbacks near Boundaries of Small-scale Magnetic Flux Ropes in the Young Solar Wind from Parker Solar Probe Observations
• Solar Alfvenic Pulses and Mesoscale Solar Wind
• Numerical simulations of temperature anisotropy instabilities stimulated by suprathermal protons
• Complexity-entropy analysis of solar photospheric turbulence: Hinode images of magnetic and Poynting fluxes
• Magnetic Switchback Occurrence Rates in the Inner Heliosphere: Parker Solar Probe and 1 au