Investigating Nonequilibrium Ionization and Recombination Processes in Solar Wind and Transient Plasma
Creators: name: Rivera, Yeimy
Publisher: name: My University
Year: 2020
Subjects: subject: Solar Physics
subject: Heliospheric Physics
subject: Coronal Mass Ejections
subject: Solar Wind
subject: Charge states
subject: Composition
subject: Atmospheric, Oceanic and Space Sciences
subject: Science

description: In this work, I investigated the evolution of coronal mass ejections (CMEs) and the solar wind by combining remote sensing, in situ observations, and nonequilibrium ionization modeling using the Michigan Ionization Code (MIC). The work investigates physical processes governing the plasma’s radial evolution and the injection of energy to the system. The aim of this thesis is to investigate low ionized charge states in CMEs and He+ in the solar wind to understand their origin and formation. Through simulations of charge states with the MIC, the modeling work reconstructed the thermodynamic evolution of several plasma structures within the expansion of a coronal mass ejection (CME) by examining heliospheric ion composition within the ejecta. The reconstructed CME contained rare, low charge states, which are often absent within CMEs, along with typical highly ionized coronal plasma. Modeling results show that the source of the low ionized material in the CME measurements is from prominence material and is not a result of recombination from cooling of the plasma. However, part of the prominence also exists in a highly ionized form. These results provide important constraints to the evolution of prominence material that is often observed at the Sun but rarely measured in situ. In addition, this study indicated the CME components experienced rapid, continuous, and non-uniform heating as they travelled away from the Sun. Motivated by these results, I identified useful spectral lines to study the eruption with future solar telescopes. This study investigated the diagnostic potential of several spectral lines spanning the EUV to near-Infrared and ranging between chromospheric and sub-flare temperatures to enable a comprehensive examination of solar eruptions that can be coupled with in situ and nonequilibrium modeling. I present a list of recommended spectral lines along with a discussion of their diagnostic capability. Results show that several of the most observable lines will be within the planned observations of future solar telescopes; Daniel K. Inouye Solar Telescope (DKIST), and Upgraded COronal Multi-channel Polarimeter (UCoMP), and instruments on Solar Orbiter, e.g. Spectral Imaging of the Coronal Environment (SPICE) and Multi-Element Telescope for Imaging and Spectroscopy (METIS). Furthermore, I investigated the presence of singly ionized He in the solar wind, that are outside of CME cores and pick up ions, to determine their origin and formation mechanism using the MIC. Current ionization models of the solar wind cannot account for the enhanced density of He+ observed at 1AU, therefore we reconcile the additional He+ through charge exchange of solar wind alphas and outgassed interplanetary dust neutrals. We find that charge exchange processes can be an important mechanism in the formation of solar He+ from alpha particles below 10-15Rsun, and due to this, may potentially shape ion densities for other species in the solar wind as well.