Exploring Solar Wind Origins and Connecting Plasma Flows from the <i>Parker Solar Probe</i> to 1 au: Nonspherical Source Surface and Alfv\ enic Fluctuations

Author
Keywords
Abstract
<p>The magnetic field measurements of the FIELDS instrument on the Parker Solar Probe (PSP) have shown intensities, throughout its first solar encounter, that require a very low source surface (SS) height ( <em>R</em>\&nbsp;SS\&nbsp;⩽1.8<em>R</em>\&nbsp;⊙\&nbsp;\&nbsp;RSS⩽1.8R⊙ ) to be reconciled with magnetic field measurements at the Sun via potential field extrapolation (PFSS). However, during PSP\textquoterights second encounter, the situation went back to a more classic SS height ( <em>R</em>\&nbsp;SS\&nbsp;⩽2.5<em>R</em>\&nbsp;⊙\&nbsp;\&nbsp;RSS⩽2.5R⊙ ). Here we use high-resolution observations of the photospheric magnetic field (Solar Dynamics Observatory/Helioseismic and Magnetic Imager) to calculate neutral lines and boundaries of the open field regions for SS heights from 1.2 to 2.5 R<sub>☉</sub> using an evolving PFSS model and the measured solar wind speed to trace the source of the wind observed by PSP to the low corona and photosphere. We adjust R<sub>SS</sub> to get the best match for the field polarity over the period 2018 October-November and 2019 March-April, finding that the best fit for the observed magnetic field polarity inversions requires a nonspherical SS. The geometry of the coronal hole boundaries for different R<sub>SS</sub> is tested using the PSP perihelion passes, 3D PFSS models, and LASCO/C2 observations. We investigate the sources of stronger-than-average magnetic fields and times of Alfv\ enic fast and slow wind. Only some of the strongly Alfv\ enic slow wind streams seen by PSP survive and are observed at 1 au: the origins and peculiar topology of the background in which they propagate is discussed.</p>
Year of Publication
2020
Journal
The Astrophysical Journal Supplement Series
Volume
246
Number
Number of Pages
54
Date Published
02/2020
URL
https://iopscience.iop.org/article/10.3847/1538-4365/ab61f4
DOI
10.3847/1538-4365/ab61f4