Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsh21a0494r&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SH21A-0494
Physics
2111 Ejecta, Driver Gases, And Magnetic Clouds, 2164 Solar Wind Plasma, 7513 Coronal Mass Ejections
Scientific paper
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 (CH), coronal mass ejection (CME), and interstream (IS) 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. By applying the Genesis algorithm results to ACE/SWICS abundance and charge-state data, we show that the solar wind speed history can be used to further discriminate between the IS and CH flow types. By using a lower speed threshold for fast-to-slow than for slow-to-fast regime transitions, the Genesis algorithm effectively compensates for evolution effects that are due to transit to 1 AU. Furthermore, we show that for some signatures, CME composition is independent of speed, having a composition most typical of the slow wind < 400\ km\ s-1. However, differences between CMEs and the slow wind exist for He/H and O8+. Also, it is seen that larger helium enhancements are found in faster CMEs. The algorithm is successfully isolating the CME population, and thus protecting the CH and IS samples from contamination by CME material.
Barraclough Bruce L.
Dors Eric E.
Neugebauer Matthias
Reinard Alysha
Reisenfeld Daniel Brett
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