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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 1 to 3 of 3 (0.037 seconds)Spelling suggestions: "subject:"chromosphere."" "subject:"thermospheric.""
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Modelling chromospheric evaporation in response to coronal heatingJohnston, Craig David January 2018 (has links)
This thesis presents a new computationally efficient method for modelling the response of the solar corona to the release of energy. During impulsive heating events, the coronal temperature increases which leads to a downward heat flux into the transition region (TR). The plasma is unable to radiate this excess conductive heating and so the gas pressure increases locally. The resulting pressure gradient drives an upflow of dense material, creating an increase in the coronal density. This density increase is often called chromospheric evaporation. A process which is highly sensitive to the TR resolution in numerical simulations. If the resolution is not adequate, then the downward heat flux jumps over the TR and deposits the heat in the chromosphere, where it is radiated away. The outcome is that with an under-resolved TR, major errors occur in simulating the coronal density evolution. We address this problem by treating the lower transition region as a discontinuity that responds to changing coronal conditions through the imposition of a jump condition that is derived from an integrated form of energy conservation. In this thesis, it is shown that this method permits fast and accurate numerical solutions in both one-dimensional and multi-dimensional simulations. By modelling the TR with this appropriate jump condition, we remove the influence of poor numerical resolution and obtain the correct evaporative response to coronal heating, even when using resolutions that are compatible with multi-dimensional magnetohydrodynamic simulations.
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Intera??o estrela planeta: sobre o magnetismo de planetas gigantes gasososNascimento, Sanzia Alves do 16 February 2012 (has links)
Made available in DSpace on 2014-12-17T15:14:59Z (GMT). No. of bitstreams: 1
SanziaAN_TESE.pdf: 6049434 bytes, checksum: 6a97e62e04daa321fddc66de5d006ee5 (MD5)
Previous issue date: 2012-02-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this thesis we analyze the effects that the presence of a near gas giant planet can
cause in its host star. It has been argued that the star planet interaction can cause
changes in the coronal and chromospheric stellar activity. With this in mind, we analyze
a sample of 53 extrasolar planets orbiting F, G and K main sequence stars, among
them three super-Earths. In this analysis, we look for evidence of changes in the
chromospheric activity due to the proximity of the giant planet. We show that, so far,
there is not enough evidence to support such a hypothesis. Making use of the same
sample and also taking in account available data for the Solar System, we revisit the
so-called magnetic Bode s law. This law proposes the existence of a direct relationship
between magnetism and rotation. By using estimations for the stellar and planetary
magnetic momentM and the angular momentumL, we construct a Blackett s diagram
(logL 􀀀logM). In this diagram is evident that the magnetic Bode s law is valid for both
the Solar System and the new planetary systems / Nesta tese s?o analisados os efeitos que a presen?a de um planeta gigante gasoso
pr?ximo causa em sua estrela hospedeira. Tem se discutido que a intera??o estrela -
planeta possa provocar mudan?as na atividade cromosf?rica e coronal estelar. Tendo
isto em mente, analisamos uma amostra composta por 53 planetas extrassolares orbitando
estrelas F, G e K da sequ?ncia principal, dentre os quais tr?s superterras. Nesta
an?lise, buscamos ind?cios de mudan?as na atividade cromosf?rica estelar devido ?
proximidade do planeta gigante. Mostramos que n?o existem evid?ncias suficientes
que corroborem tal hip?tese. Fazendo uso desta mesma amostra e de dados dispon?veis
na literatura para o Sistema Solar, revisitamos a chamada lei magn?tica de
Bode. Esta lei prop?e a exist?ncia de uma rela??o direta entre magnetismo e rota??o.
Atrav?s de estimativas para o momento magn?tico M e para o momentum angular
L destes objetos, constru?mos e analisamos detalhadamente o diagrama de Blackett
(logL 􀀀 logM). Neste diagrama ficou evidente que a lei magn?tica de Bode ? v?lida
tanto para o Sistema Solar quanto para os novos sistemas planet?rios
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Kleinskalige Magnetfelder der Sonne und ihr Einfluß auf Chromosphäre, Übergangszone und Korona / Small-Scale Solar Magnetic Fields and their Influence upon Chromosphere, Transition Region and CoronaWilken, Volker 28 June 2001 (has links)
No description available.
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