A Steady-State Picture of Solar Wind Acceleration and Charge State Composition Derived from a Global Wave-Driven MHD Model

Authors
Oran, R.; Landi, E.; Van Der Holst, B.; Lepri, S. T.; Vasquez, Alberto Marcos; Nuevo, Federico Alberto; Frazin, R.; Manchester, W.; Sokolov, I.; Gombosi, T. I.
Publication Year
2015
Language
English
Format
article
Status
Published version
Description
The higher charge states found in slow (<400 km s−1) solar wind streams compared to fast streams have supported the hypothesis that the slow wind originates in closed coronal loops, and released intermittently through reconnection. Here we examine whether a highly ionized slow wind can also form along steady and open magnetic field lines. We model the steady-state solar atmosphere using AWSoM, a global magnetohydrodynamic model driven by Alfv{´e}n waves, and apply an ionization code to calculate the charge state evolution along modeled open field lines. This constitutes the first charge states calculation covering all latitudes in a realistic magnetic field. The ratios $O^{+7}/O^{+6}$ and $C^{+6}/C^{+5}$ are compared to in-situ Ulysses observations, and are found to be higher in the slow wind, as observed; however, they are under-predicted in both wind types. The modeled ion fractions of S, Si, and Fe are used to calculate line-of-sight intensities, which are compared to EIS observations above a coronal hole. The agreement is partial, and suggests that all ionization rates are under-predicted. Assuming the presence of suprathermal electrons improved the agreement with both EIS and Ulysses observations; importantly, the trend of higher ionization in the slow wind was maintained. The results suggest there can be a sub-class of slow wind that is steady and highly ionized. Further analysis shows it originates from coronal hole boundaries (CHB), where the modeled electron density and temperature are higher than inside the hole, leading to faster ionization. This property of CHBs is global, and observationally supported by EUV tomography.
Fil: Oran, R.. University Of Michigan; Estados Unidos
Fil: Landi, E.. University Of Michigan; Estados Unidos
Fil: Van Der Holst, B.. University Of Michigan; Estados Unidos
Fil: Lepri, S. T.. University Of Michigan; Estados Unidos
Fil: Vasquez, Alberto Marcos. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: Nuevo, Federico Alberto. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: Frazin, R.. University Of Michigan; Estados Unidos
Fil: Manchester, W.. University Of Michigan; Estados Unidos
Fil: Sokolov, I.. University Of Michigan; Estados Unidos
Fil: Gombosi, T. I.. University Of Michigan; Estados Unidos
Subject
Sun: heliosphere
techniques: spectroscopic
turbulence
Astronomía
Ciencias Físicas
CIENCIAS NATURALES Y EXACTAS
Access level
Open access
License
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repository
CONICET Digital (CONICET)
Institution
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identifier
oai:ri.conicet.gov.ar:11336/17853