Compositional metrics of fast and slow Alfvenic solar wind emerging from coronal holes and their boundaries
arxiv(2023)
摘要
We seek to understand the composition and variability of fast (FSW) and slow
Alfvenic solar wind (SASW) emerging from coronal holes (CH). We leverage an
opportune conjunction between Solar Orbiter and Parker Solar Probe (PSP) during
PSP Encounter 11 to include compositional diagnostics from the Solar Orbiter
heavy ion sensor (HIS) as these variations provide crucial insights into the
origin and nature of the solar wind. We use Potential Field Source Surface
(PFSS) and Magnetohydrodynamic (MHD) models to connect the observed plasma at
PSP and Solar Orbiter to its origin footpoint in the photosphere, and compare
these results with the in situ measurements. A very clear signature of a
heliospheric current sheet (HCS) crossing as evidenced by enhancements in low
FIP elements, ion charge state ratios, proton density, low-Alfvenicity, and
polarity estimates validates the combination of modeling, data, and mapping. We
identify two FSW streams emerging from small equatorial coronal holes (CH) with
low ion charge state ratios, low FIP bias, high-Alfvenicity, and low footpoint
brightness, yet anomalously low alpha particle abundance for both streams. We
identify high-Alfvenicity slow solar wind emerging from the over-expanded
boundary of a CH having intermediate alpha abundance, high-Alfvenicity, and
dips in ion charge state ratios corresponding to CH boundaries. Through this
comprehensive analysis, we highlight the power of multi-instrument conjunction
studies in assessing the sources of the solar wind.
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