Coronal Mass Ejections in the Low Solar Corona: Ion Composition and EUV Diagnostics A Coupled Investigation using Remote-Sensing Observations and In-situ Measurements

[摘要] Coronal Mass Ejections (CMEs) are spectacular solar transients that deposit vast amounts of plasma and magnetic energy into the heliosphere. The build-up and release of plasma and energy during CME events are critically important to science and society. They involve processes at the center of the heating and evolution of the solar atmosphere that are also relevant across a range of other scientific disciplines. Furthermore, society’s interconnectedness and dependence on technology makes us extremely vulnerable to solar activity and major CME eruptions, which can paralyze our indispensable space-borne and ground-based infrastructure. This dissertation presents a study of the evolution of geo-effective CMEs using an array of remote-sensing observations, in-situ measurements, an ionization model, numerical simulations, and diagnostic techniques. These analyses attempt an extensive observational account of the evolution of the dynamics, energetics, and composition of these consequential transients. The overarching vision in these series of investigations is to develop groundwork for connecting the unprecedented remote-sensing and in-situ observations from future missions of Parker Solar Probe and Solar Orbiter. Three central CME science topics addressed here are: (1) in-situ signatures of CME processes in the low solar corona, (2) the evolution of filament composition in the low solar corona, and (3) the evolution of filament dynamics and energetics in the low solar corona.First, a detailed analysis of in-situ observations of 14 years of Earth-intercepting ICMEs and associated composition anomalies is presented. 45% of these ICMEs (called ;;depleted ICMEs’) contained distinct periods of anomalous heavy-ion charge state composition and peculiar ion thermal properties (called ;;Depletion Regions’). The most consistent characteristics of the Depletion Regions were (1) depleted fully stripped ions of helium, carbon, nitrogen, and oxygen, and (2) exposure to sources of heating before the charge states froze-in. Using results from two prominent CME models, a preliminary investigation into the possibility of the Depletion Region plasma being an in-situ signature of magnetic reconnection in the low solar corona is conducted.To connect near-Earth observations of ICMEs to their evolution in the low solar corona, a case-study of a geo-effective ICME is presented. The event was traced to the Sun using SOHO/LASCO and STEREO/SECCHI observations. The filament eruption associated with the CME was ;;followed’ in multi-wavelength SDO/AIA and STEREO/EUVI images in an attempt to quantify its behavior at high-cadence. Estimates of kinematics, dynamics, and the ionization history of the filament eruption during the first hour of its journey are discussed. However, the diagnostic technique used to estimate temperature and density of the filament assumed a non-emitting plasma. Since AIA 304 Å observations where contributions from emission may be significant was used, uncertainties that were difficult to quantify were introduced to the results. This motivated the final portion of this dissertation.A new EUV diagnostic technique is introduced that accounts for absorption as well as emission contributions from emitting channels such as 304 Å. This diagnostic technique can be equally applied to emitting and non-emitting channels, paving the way for more realistic discussion of the heating and energetics of the transient plasmas using a wider range of observations. Presented is a comparison between the results using this new diagnostic technique with the results derived when 304 Å He II emission was not considered. Improved and more precise high-cadence estimates of the evolution of filament density, temperature, speed, ionization history, and energetics are discussed.

[发布机构] University of Michigan

[效力级别] Solar EUV Diagnostics

[关键词] Coronal Mass Ejections;Solar EUV Diagnostics;Solar-Terrestrial Relations;Remote-Sensing Observations of the Sun;Solar Wind: In-situ Solar Measurements;Atmospheric;Oceanic and Space Sciences;Science;Atmospheric, Oceanic & Space Science