Composition Structure of Interplanetary Coronal Mass Ejections From Multispacecraft Observations, Modeling, and Comparison with Numerical Simulations

We present an analysis of the ionic composition of iron for two interplanetary coronal mass ejections observed in May 21-23 2007 by the ACE and STEREO spacecraft in the context of the magnetic structure of the ejecta flux rope, sheath region, and surrounding solar wind flow. This analysis is made possible due to recent advances in multispacecraft data interpolation, reconstruction, and visualization as well as results from recent modeling of ionic charge states in MHD simulations of magnetic breakout and flux cancellation CME initiation. We use these advances to interpret specific features of the ICME plasma composition resulting from the magnetic topology and evolution of the CME. We find that in both the data and our MHD simulations, the flux ropes centers are relatively cool, while charge state enhancements surround and trail the flux ropes. The magnetic orientation of the ICMEs are suggestive of magnetic breakout-like reconnection during the eruption process, which could explain the spatial location of the observed iron enhancements just outside the traditional flux rope magnetic signatures and between the two ICMEs. Detailed comparisons between the simulations and data were more complicated, but a sharp increase in high iron charge states in the ACE and STEREO-A data during the second flux rope corresponds well to similar features in the flux cancellation results. We discuss the prospects of this integrated in-situ data analysis and modeling approach to advancing our understanding of the unified CME-to-ICME evolution.Comment: Accepted for submission to The Astrophysical Journa

Comparison between average charge states and abundances of ions in CMEs and the slow solar wind

We present results from a comparison of CME and slow solar wind ejecta detected at the ACE spacecraft in 1998 and 1999. CME events were identified based on the observation of counterstreaming halo electrons from SWEPAM data. We discuss the compositional signatures in the framework of a recent model of the coronal magnetic field by Fisk and Schwadron [1]. We conclude that slow solar wind and CMEs have a common source in the corona, presumably coronal loops. The largest amount of fractionation is found in helium and in charge state composition. The former is related to collisional effects in the corona and the latter is attributed to the anomalous heating and propagation properties of some CMEs. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87585/2/139_1.pd

Comparison Of The Genesis Solar Wind Regime Algorithm Results With Solar Wind Composition Observed By ACE

Launched on 8 August 2001, the NASA Genesis mission is now collecting samples of the solar wind in various materials, and will return those samples to Earth in 2004 for analysis. A primary science goal of Genesis is the determination of the isotopic and elemental composition of the solar atmosphere from the solar wind material returned. In particular, Genesis will provide measurements of those species that are not provided by solar and in situ observations. We know from in situ measurements that the solar wind exhibits compositional variations across different types of solar wind flows. Therefore, Genesis exposes different collectors to solar wind originating from three flow types: coronal hole, coronal mass ejection (CME), and interstream flows. Flow types are identified using in situ measurements of solar wind protons, alphas, and electrons from electrostatic analyzers carried by Genesis. The flow regime selection algorithm and subsequent collector deployment on Genesis act autonomously. We present an assessment of composition variations of O, He, and Mg ions observed by ACE/SWICS concurrent with Genesis observations, and compare these to the Genesis algorithm decisions. Not only does this serve as a test of the algorithm, the compilation of composition vs. regime will be important for comparison to the abundances determined from sample analysis at the end of the mission. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87657/2/632_1.pd

Coronal and solar wind elemental abundances

Coronal elemental abundances, as compared with abundances in the solar wind and solar energetic particles, provide the means for connecting solar wind gas with its coronal source. Comparison of coronal abundances with photospheric values shows fractionation with the ionization potential of the atom, providing important, though not yet fully understood, information about the exchange of material between corona and chromosphere. Fractionation due to gravitational settling provides clues about flows within the corona. In this paper, we discuss the uncertainties of abundance determinations with spectroscopic techniques and in situ measurements, we survey the ranges of abundance variations in both the corona and solar wind, and we discuss the progress in correlating solar wind features with their coronal sources. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87583/2/49_1.pd

Comparison of the Genesis solar wind regime algorithm results with solar wind composition observed by ACE

Launched on 8 August 2001, the NASA Genesis mission is now collecting samples of the solar wind in various materials, and will return those samples to Earth in 2004 for analysis. A primary science goal of Genesis is the determination of the isotopic and elemental composition of the solar atmosphere from the solar wind material returned. In particular, Genesis will provide measurements of those species that are not provided by solar and in situ observations. We know from in situ measurements that the solar wind exhibits compositional variations across different types of solar wind flows. Therefore, Genesis exposes different collectors to solar wind originating from three flow types: coronal hole, coronal mass ejection (CME), and interstream flows. Flow types are identified using in situ measurements of solar wind protons, alphas, and electrons from electrostatic analyzers carried by Genesis. The flow regime selection algorithm and subsequent collector deployment on Genesis act autonomously. We present an assessment of composition variations of O, He, and Mg ions observed by ACE/SWICS concurrent with Genesis observations, and compare these to the Genesis algorithm decisions. Not only does this serve as a test of the algorithm, the compilation of composition vs. regime will be important for comparison to the abundances determined from sample analysis at the end of the mission