Solar wind rotation rate and shear at coronal hole boundaries, possible consequences for magnetic field inversions

Abstract

In-situ measurements by several spacecraft have revealed that the solar wind is frequently perturbed by transient structures (magnetic folds, jets, waves, flux-ropes) that propagate rapidly away from the Sun over large distances. Parker Solar Probe has detected frequent rotations of the magnetic field vector at small heliocentric distances, accompanied by surprisingly large solar wind rotation rates. The physical origin of such magnetic field bends, the conditions for their survival across the interplanetary space, and their relation to solar wind rotation are yet to be clearly understood. We traced measured solar wind flows from the spacecraft position down to the surface of the Sun to identify their potential source regions and used a global MHD model of the corona and solar wind to relate them to the rotational state of the low solar corona. We identified regions of the solar corona for which solar wind speed and rotational shear are important and long-lived, that can be favourable to the development of magnetic deflections and to their propagation across extended heights in the solar wind. We show that coronal rotation is highly structured and that enhanced flow shear develops near the boundaries between coronal holes and streamers, around and above pseudo-streamers, even when such boundaries are aligned with the direction of solar rotation. A large fraction of the switchbacks identified by PSP map back to these regions, both in terms of instantaneous magnetic field connectivity and of the trajectories of wind streams that reach the spacecraft. These regions of strong shears are likely to leave an imprint on the solar wind over large distances and to increase the transverse speed variability in the slow solar wind. The simulations and connectivity analysis suggest they can be a source of the switchbacks and spikes observed by Parker Solar Probe.

arXiv commentAccepted for publication in Astronomy & Astrophysics

References in corpus (13)

• The Solar Orbiter mission -- Science overview
• The Solar Probe Cup on Parker Solar Probe
• In-situ switchback formation in the expanding solar wind
• Shear-Driven Transition to Isotropically Turbulent Solar Wind Outside the Alfven Critical Zone
• Magnetic field kinks and folds in the solar wind
• Coupling the solar dynamo and the corona: wind properties, mass and momentum losses during an activity cycle
• Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind
• Coronal-Jet-Producing Minifilament Eruptions as a Possible Source of Parker Solar Probe (PSP) Switchbacks
• Relating streamer flows to density and magnetic structures at the Parker Solar Probe
• The Evolution of Inverted Magnetic Fields Through the Inner Heliosphere
• Flux-tube geometry and solar wind speed during an activity cycle
• Statistical properties of coronal hole rotation rates: Are they linked to the solar interior?
• Source-dependent properties of two slow solar wind states

Cited by in corpus (5)

• Solar Orbiter Observations of the Kelvin-Helmholtz Instability in the Solar Wind
• On the Generation and Evolution of Switchbacks and the Morphology of Alfvénic Transition: Low Mach-number Boundary Layers
• MOVES V. Modelling star-planet magnetic interactions of HD 189733
• Accounting for Differential Rotation in Calculations of the Sun's Angular Momentum-loss Rate
• Effect of Differential Rotation on Magnetic Braking of Low-Mass and Solar-Like Stars: A Proof-of-Concept Study