Compositional metrics of fast and slow Alfvenic solar wind emerging from coronal holes and their boundaries

TL;DR

This study uses multi-instrument data and modeling to analyze the composition and origins of fast and slow Alfvenic solar wind from coronal holes, revealing distinct signatures and boundary behaviors.

Contribution

It introduces a combined observational and modeling approach to distinguish solar wind sources and characteristics from coronal holes and their boundaries.

Findings

Fast solar wind from small equatorial coronal holes shows low FIP bias and high Alfvenicity.

Slow solar wind from CH boundaries exhibits intermediate alpha abundance and dips in ion charge states.

Heliospheric current sheet crossing signatures validate the data-model integration.

Abstract

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.