MARC details
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05408nam a2200241Ia 4500 |
| 003 - CONTROL NUMBER IDENTIFIER |
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IN-BaIIA |
| 005 - DATE AND TIME OF LATEST TRANSACTION |
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20211109144921.0 |
| 008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION |
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211028s9999 xx 000 0 eng d |
| 040 ## - CATALOGING SOURCE |
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| Transcribing agency |
IIA Library |
| 080 ## - UNIVERSAL DECIMAL CLASSIFICATION NUMBER |
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| Universal Decimal Classification number |
043:52 |
| Item number |
RAN |
| 100 ## - MAIN ENTRY--PERSONAL NAME |
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| Personal name |
Rangarajan, K. E. |
| 9 (RLIN) |
17058 |
| Relator term |
Author |
| 245 #4 - TITLE STATEMENT |
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| Title |
The effect of the partial redistribution of spectral line formation |
| Statement of responsibility, etc. |
K. E. Rangarajan |
| Medium |
[Ph.D Thesis] |
| 260 ## - PUBLICATION, DISTRIBUTION, ETC. |
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| Place of publication, distribution, etc. |
Bangalore |
| Name of publisher, distributor, etc. |
Indian Institute of Astrophysics |
| Date of publication, distribution, etc. |
1987 |
| 300 ## - PHYSICAL DESCRIPTION |
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| Extent |
114p. |
| 502 ## - DISSERTATION NOTE |
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| Degree type |
Doctor of Philosophy |
| Name of granting institution |
Indian Institute of Astrophysics, Bangalore |
| Year degree granted |
1987 |
| 520 ## - SUMMARY, ETC. |
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| Summary, etc. |
The main effort of this study is concentrated on<br/>ascertaining the role of partial redistribution(PRD> functions<br/>in the process of spectral line formation. The effects of<br/>angle averaged R I' R II' RIIIa nd R V<br/>redistribution with<br/>isotropic phase function are studied. We have compared these<br/>results with those obtained using complete redistribution<br/>(CRD) . Transfer equation with plane parallel geometry is<br/>solved using the Discrete space theory technique of Grant and<br/>Hunt (1969) . Various types of boundary conditions<br/>considered. The following results are the new and important<br/>conclusions of this study.<br/>In this study, we find that for a purely scattering<br/>optically thick medium, RI function produces deeper absorption<br/>profile compared to other functions. The redistribution<br/>function R II is more coherent than Rv and R v is more coherent<br/>than R: u:x in the wings. The more non-coherent the<br/>redistribution function is, the higher would be the emergent<br/>intensity in the Doppler core. If thermal sources are present<br/>in the medium and if there is incident radiation on the lower<br/>boundary, all the redistribution functions give the same<br/>intensity, in the core. But in the wings, the more non-coherent<br/>the redistribution is, the higher would be the intensity. The<br/>presence of continuous opacity makes the spectral lines appear<br/>weak. Their effects are more pronounced compared to that of the<br/>thermal sources in the medium and are present for any type of<br/>redistribution mechanism. In high optical depth situations,<br/>the R type of redistribution allows the photons to diffuse<br/>to the line centre and increase the intensity there.<br/>In the third chapter, coherent and non-coherent<br/>electron scattering combined with complete and partial<br/>redistribution by atoms are studied for some parameterized<br/>models. Since this problem is characterized by two frequency<br/>scales, one for the atoms and the other for the electrons, two<br/>types of frequency quadrature are required to cover the effect<br/>of both the processes. Though the basic equations are solved<br/>within the framework of Discrete space theory, the frequency<br/>quadrature points, normalization, segmenting the problem into<br/>core and wing regions and the iteration procedure all follow<br/>that of Auer and Mihalas (1968). We obtain the following new<br/>result: If the coherent electron scattering is the only<br/>continuous opacity source, we find that the more non-coherent<br/>the redistribution by atoms is, the higher the value of the<br/>mean intensity in the wings for optically thick media. The<br/>non-coherent electron scattering combined with PRD fills up<br/>the core and hence one gets higher fluxes in the core compared<br/>to coherent electron scattering_<br/>We investigate the deviation of absorption and<br/>emission profiles from each other for a two level atom with<br/>angle avera9~d redistribution functions. The corr~ct<br/>expression for the source function derived by Baschek,Mihalas<br/>and Oxenius (1981) is used to solve consistently for the<br/>emission profile and the radiation field. From this study, we<br/>get the following new and important results: The absorption<br/>and emission profiles do not deviate from each other in the<br/>Doppler core for any redistribution function even if the<br/>stimulated emission term is important. The devition of<br/>absorption and emission profiles in the wing is more for<br/>coherent type of redistribution function. R xxx redistribution<br/>gives identical absorption and emission profiles and so one<br/>can approximate RIII by CRD for all practical purposes.<br/>The effects of small macroscopic velocity fields on<br/>Ca II Hand K lines are given in chapter 5. The atomic model<br/>chosen contains the lower most five levels and the continuum.<br/>radiative transfer equation and statistical equilibrium<br/>equations are solved simultaneously using equivalent two level<br/>atom method. A schematic chromospheric type of atmosphere is<br/>considered. The emergent profiles are calculated for the<br/>systematic expanding velocities 0.0, 0.5 and 1.0 (velocities<br/>at the outer boundaries expressed in mean thermal units). We<br/>obtain the following significant results: Even though the<br/>velocities are small, they seem to affect the shapes of the H<br/>and K profiles considerably. A single peak emission instead of<br/>a double• peaked emission is obtained for the K line with v<br/>~ 1 and p = 0.79. ( ~ = cos8 , 8 is the angle of the ray to<br/>the normal at the surface.). The small velocities do not<br/>affect the infrared triplet lines significantly. |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Astronomy and Astrophysics Thesaurus |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Ph.D Thesis |
| 9 (RLIN) |
1344 |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Spectral line formation |
| 9 (RLIN) |
14139 |
| 700 ## - ADDED ENTRY--PERSONAL NAME |
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| Personal name |
A. Peraiah |
| Relator term |
Supervisor |
| 9 (RLIN) |
48850 |
| 856 ## - ELECTRONIC LOCATION AND ACCESS |
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| Uniform Resource Identifier |
<a href="http://prints.iiap.res.in/handle/2248/126">http://prints.iiap.res.in/handle/2248/126</a> |
| Link text |
Click Here to Access eThesis |
| 942 ## - ADDED ENTRY ELEMENTS (KOHA) |
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| Koha item type |
Thesis & Dissertations |
| Source of classification or shelving scheme |
Universal Decimal Classification |
