Magnetic reconnection as an erosion mechanism for magnetic switchbacks

Abstract

Magnetic switchbacks are localised polarity reversals in the radial component of the heliospheric magnetic field. Observations from Parker Solar Probe (PSP) have shown that they are a prevalent feature of the near-Sun solar wind. However, observations of switchbacks at 1 au and beyond are less frequent, suggesting that these structures evolve and potentially erode through yet-to-be identified mechanisms as they propagate away from the Sun. We analyse magnetic field and plasma data from the Magnetometer and Solar Wind Analyser instruments aboard Solar Orbiter between 10 August and 30 August 2021. During this period, the spacecraft was 0.6 to 0.7 au from the Sun. We identify three instances of reconnection occurring at the trailing edge of magnetic switchbacks, with properties consistent with existing models describing reconnection in the solar wind. Using hodographs and Walen analysis methods, we test for rotational discontinuities (RDs) in the magnetic field and reconnection-associated outflows at the boundaries of the identified switchback structures. Based on these observations, we propose a scenario through which reconnection can erode a switchback and we estimate the timescales over which this occurs. For our events, the erosion timescales are much shorter than the expansion timescale and thus, the complete erosion of all three observed switchbacks would occur well before they reach 1 au. Furthermore, we find that the spatial scale of these switchbacks would be considerably larger than is typically observed in the inner heliosphere if the onset of reconnection occurs close to the Sun. Hence, our results suggest that the onset of reconnection must occur during transport in the solar wind in our cases. These results suggest that reconnection can contribute to the erosion of switchbacks and may explain the relative rarity of switchback observations at 1 au.

Accepted for publication in Astronomy & Astrophysics 05/05/2023

References in corpus (10)

• Switchbacks in the near-Sun magnetic field: long memory and impact on the turbulence cascade
• In-situ switchback formation in the expanding solar wind
• 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
• Characteristic scales of magnetic switchback patches near the Sun and their possible association with solar supergranulation and granulation
• Evolution of switchbacks in the inner Heliosphere
• The Evolution of Inverted Magnetic Fields Through the Inner Heliosphere
• On the properties of Alfvénic switchbacks in the expanding solar wind: the influence of the Parker spiral