Computer Science – Sound
Scientific paper
Feb 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt........23s&link_type=abstract
Thesis (PhD). BOSTON UNIVERSITY, Source DAI-B 61/08, p. 4211, Feb 2001, 175 pages.
Computer Science
Sound
1
Scientific paper
The solar system moves through the Galaxy, interacting with the interstellar medium and magnetic field. The solar wind moves radially away from the Sun and effectively shields the inner heliosphere from the immediate interstellar neighborhood, or Very Local Interstellar Medium (VLISM). The VLISM consists of both ionized and neutral (H, He, O, etc.) gas. The ionized VLISM component is excluded from the heliosphere and forms a tangential discontinuity, the heliopause, with the solar wind plasma. The neutral VLISM component can enter the heliosphere, but is filtered at the interface region due to coupling with VLISM ions. Once past the interface region, VLISM atoms are influenced by solar gravity, solar radiation pressure, and ionization processes. Measurements of the filtered and processed neutrals can be used to derive conditions within the ambient VLISM and heliospheric interface region. Specifically, fully resolved neutral line profiles and velocity distributions are used to constrain models of the interface region and inner heliospheric processes. Neutral H, the most abundant VLISM species, has a bright scattered line at Lyman α (1215.66 Å). However, velocity distribution measurements of H Lyman α require both spacecraft platforms to overcome atmospheric opacity at this wavelength and high spectral resolution to separate VLISM emission from the dominant geocoronal emission. I, as part of a Boston University team, have built and flown a sounding rocket experiment to make far ultraviolet (FUV) emission measurements of processed VLISM neutral hydrogen near the Earth. I have used the resolving capabilities of SCARI (Self-Compensating All- Reflecting Interferometer), a novel interferometric spectrograph, to make an H Lyman α line profile and velocity distribution measurement. I describe SCARI and two sounding rocket flights in November, 1997 and April, 1998. From these data, I use theoretical line profile models to determine VLISM conditions and solar influences; specifically, the best model fit finds post interface region VLISM H density, temperature and velocity to be 0.17 cm-3, 10000 K, and <=22 km/s, respectively. I conclude by comparing these values to past studies and discussing the implications of these results on heliospheric interface theory. I have shown how high spectral resolution measurements of neutral hydrogen in the interplanetary medium, such as SCARI's, can help the scientific community better understand the solar wind-interstellar wind interaction and determine near solar processing of interplanetary material.
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