Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Physics

Language

English (en)

Date of Award

January 2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Charles Hohenberg

Abstract

The Genesis mission collected samples of solar wind: SW) for 853 days and returned them to Earth for analysis. There are several processes that have the potential to significantly alter the composition between the time when SW ions are accelerated away from the sun, to the time the laboratory measurements are made. This work attempts to constrain these sources of fractionation and present the best estimate of the isotopic composition of SW helium, neon, and argon implanted into two different aluminum SW collectors on board the Genesis Mission. We have conducted a diffusion experiment on a similar time scale as the Genesis mission to determine the diffusion parameters of the two different aluminum collector materials and to quantify the changes in the measured ratios due to diffusive losses for the light noble gases. The results of this experiment show that the polished Al collector is not sufficiently retentive of the light noble gases to be a reliable collector for the light gases, but that the composition of the light gases implanted in the Al on sapphire collector does not show a measurable effect due to thermal diffusion. The Genesis mission collected separate samples of different types: `regimes') of SW: low-speed, high-speed, and coronal mass ejections. Compositional differences between the different SW regimes: especially the low-speed and high-speed SW) are thought to provide a measure of possible fractionation during the acceleration of the SW. By making high-precision isotopic measurements on collectors of the three SW regimes, we have put strict upper limits on the difference between the low-speed and high-speed SW regimes: 20Ne/22Ne < 0.24 ± 0.37% and 36Ar/38Ar < 0.11 ± 0.26%. And we have made isotopic measurements of the light noble gases of the bulk SW: without selective collection of different SW regimes) from the aluminum collectors. Accounting for the sources of fractionation discussed above, I propose the following as the best current bulk SW isotopic values: 20Ne/22Ne = 13.75 ± 0.02, 21Ne/22Ne = 0.0329 ± 0.0002, and 36Ar/38Ar = 5.501 ± 0.005: all errors are 1σ).

Comments

Permanent URL: http://dx.doi.org/10.7936/K7GX48PP

Download

Share

COinS