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Switchback Patches Evolve into Microstreams via Magnetic Relaxation

Soni, Shirsh Lata; Akhavan-Tafti, Mojtaba; Suen, Gabriel Ho Hin; Kasper, Justin; Velli, Marco; De Marco, Rossana; Zhao, Liang; (2024) Switchback Patches Evolve into Microstreams via Magnetic Relaxation. The Astrophysical Journal , 977 (2) , Article 264. 10.3847/1538-4357/ad94da. Green open access

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Abstract

Switchbacks, defined as Alfvénic reversals in magnetic field polarity, can dissipate their magnetic energy with heliocentric distance. To further investigate this, two distinct solar wind parcels tracing back to a similar solar source region were examined during a radial alignment between Parker Solar Probe (@25.8RS) and Solar Orbiter (@152RS). The one caveat was that the two probes were located on opposite sides of the heliospheric current sheet during the alignment. The two parcels contained a multitude of switchbacks—the parcel closer to the Sun was characterized as a switchback patch (SBP), where background proton velocity (vp ) is comparable to the pristine solar wind (v sw), while the parcel farther from the Sun showed characteristics attributable to a microstream (MS; v p > v sw). It was found that (1) MS contains, on average, 30% fewer switchbacks than SBP, and (2) dynamic and thermal pressures decreased by up to 20% across switchback boundaries in SBP and relatively unchanged in MS. Magnetic relaxation can explain the lower number of switchbacks in MS compared to SBP. Switchback relaxation inside SBP can, in turn, accelerate plasma inside SBP over time and heliocentric distance, thus resulting in vp > v sw in MS. Therefore, it is hypothesized that magnetic relaxation of switchbacks may cause SBPs to evolve into MSs over time and heliocentric distance.

Type: Article
Title: Switchback Patches Evolve into Microstreams via Magnetic Relaxation
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/ad94da
Publisher version: https://doi.org/10.3847/1538-4357/ad94da
Language: English
Additional information: Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Keywords: Science & Technology, Physical Sciences, Astronomy & Astrophysics, WIND HELIUM ABUNDANCE, SOLAR-WIND, ALPHA-PARTICLE, EVOLUTION, SPEED, CORONA, INTERPLANETARY, RECONNECTION, LATITUDE, PROTON
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10203138
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