Plasma properties, switchback patches, and low alpha-particle abundance in slow Alfvenic coronal hole wind at 0.13 au
File(s)Woolley_al_2021.pdf (2.48 MB)
Published version
Author(s)
Type
Journal Article
Abstract
The Parker Solar Probe (PSP) mission presents a unique opportunity to study the near-Sun solar wind closer than any previous spacecraft. During its fourth and fifth solar encounters, PSP had the same orbital trajectory, meaning that solar wind was measured at the same latitudes and radial distances. We identify two streams measured at the same heliocentric distance (∼0.13 au) and latitude (∼–3∘.5) across these encounters to reduce spatial evolution effects. By comparing the plasma of each stream, we confirm that they are not dominated by variable transient events, despite PSP’s proximity to the heliospheric current sheet. Both streams are consistent with a previous slow Alfvénic solar wind study once radial effects are considered, and appear to originate at the Southern polar coronal hole boundary. We also show that the switchback properties are not distinctly different between these two streams. Low α-particle abundance (∼0.6 per cent) is observed in the encounter 5 stream, suggesting that some physical mechanism must act on coronal hole boundary wind to cause α-particle depletion. Possible explanations for our observations are discussed, but it remains unclear whether the depletion occurs during the release or the acceleration of the wind. Using a flux tube argument, we note that an α-particle abundance of ∼0.6 per cent in this low-velocity wind could correspond to an abundance of ∼0.9 per cent at 1 au. Finally, as the two streams roughly correspond to the spatial extent of a switchback patch, we suggest that patches are distinct features of coronal hole wind.
Date Issued
2021-11-01
Date Acceptance
2021-08-02
Citation
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2021, 508 (1), pp.236-244
ISSN
0035-8711
Publisher
OXFORD UNIV PRESS
Start Page
236
End Page
244
Journal / Book Title
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume
508
Issue
1
Copyright Statement
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Science and Technology Facilities Council (STFC)
The Royal Society
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000702163400018&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
ST/S000364/1
URF\R1\201286
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
magnetic fields
Sun: heliosphere
solar wind
FAST SOLAR-WIND
HELIUM ABUNDANCE
MAGNETIC-FIELD
VELOCITY
SPEED
ACCELERATION
TURBULENCE
MODEL
EVOLUTION
PROTONS
Publication Status
Published
Date Publish Online
2021-08-09