Physics
Scientific paper
Sep 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt........11l&link_type=abstract
Thesis (PhD). RUTGERS THE STATE UNIVERSITY OF NEW JERSEY - NEWARK, Source DAI-B 61/03, p. 1449, Sep 2000, 126 pages.
Physics
Scientific paper
The quiet Sun is dynamic in nature. I carried out a detailed study of some of the chromospheric structures, from fine features, namely upflow events, dark grains, rotating disk spicules, to more energetic events, like UV explosive events and a solar flare. This thesis consists of seven finished papers. Upflow events are mostly found on supergranule boundaries, they are different from disk spicules in various respects: line profile, velocity, and optical thickness distributions. Upflow events are closely associated with explosive events observed in UV lines from SOHO/SUMER. I made use of the BBSO spectrograph in obtaining high resolution spectral data by the drift scanning technique. The resultant 4-dimensional data array, Hα(x,y,t,λ), allowed the construction of a series of spectroheliograms and Dopplergrams. The detailed evolution of any feature could be examined at any given time and at various wavelengths. This kind of work has never been done before. The Beckers' cloud model was used to obtain velocity, optical thickness, Doppler width, and source function by fitting the Ha line profiles. The optical thickness of upflow events was found to be lower than that of disk spicules. The combined mass flux from upflow events and dark grains is important in explaining the predominant red shift seen in UV lines. Due to the nature of the data array, Dopplergrams can be constructed without mis-alignment problems. I searched for a rotational signature of spicules on the Doppler maps. In order to distinguish possible false signals given by overlapping multi-spicules, the method of plotting spectral intensity against spatial distance across the feature at various wavelengths was employed. A substantial number of disk spicules have been observed to display rotational signals. Finally, an M-class solar flare (BATSE #1791) with large intensity amplitude variation was selected in order to investigate the temporal behavior of X-ray and microwave spectral indices. Data were available simultaneously from CGRO/BATSE, GOES, and OVRO. An unexpected finding is that the optically thin microwave index is not in positive correlation with the hard X-ray spectral index. This observation can be explained in terms of the trap-plus- precipitation model.
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