The effect of the partial redistribution of spectral line formation (Record no. 10081)

MARC details
000 -LEADER
fixed length control field 05408nam a2200241Ia 4500
003 - CONTROL NUMBER IDENTIFIER
control field IN-BaIIA
005 - DATE AND TIME OF LATEST TRANSACTION
control field 20211109144921.0
008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION
fixed length control field 211028s9999 xx 000 0 eng d
040 ## - CATALOGING SOURCE
Transcribing agency IIA Library
080 ## - UNIVERSAL DECIMAL CLASSIFICATION NUMBER
Universal Decimal Classification number 043:52
Item number RAN
100 ## - MAIN ENTRY--PERSONAL NAME
Personal name Rangarajan, K. E.
9 (RLIN) 17058
Relator term Author
245 #4 - TITLE STATEMENT
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.
Place of publication, distribution, etc. Bangalore
Name of publisher, distributor, etc. Indian Institute of Astrophysics
Date of publication, distribution, etc. 1987
300 ## - PHYSICAL DESCRIPTION
Extent 114p.
502 ## - DISSERTATION NOTE
Degree type Doctor of Philosophy
Name of granting institution Indian Institute of Astrophysics, Bangalore
Year degree granted 1987
520 ## - SUMMARY, ETC.
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
Topical term or geographic name entry element Astronomy and Astrophysics Thesaurus
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Ph.D Thesis
9 (RLIN) 1344
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Spectral line formation
9 (RLIN) 14139
700 ## - ADDED ENTRY--PERSONAL NAME
Personal name A. Peraiah
Relator term Supervisor
9 (RLIN) 48850
856 ## - ELECTRONIC LOCATION AND ACCESS
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)
Koha item type Thesis & Dissertations
Source of classification or shelving scheme Universal Decimal Classification
Holdings
Withdrawn status Lost status Source of classification or shelving scheme Damaged status Not for loan Home library Current library Shelving location Date acquired Full call number Barcode Date last seen Price effective from Koha item type
    Universal Decimal Classification     IIA Library-Bangalore IIA Library-Bangalore General Stacks   043:52/RAN 10991 05/11/2021   Thesis & Dissertations

Powered by Koha