1,575 research outputs found
On the potential of the EChO mission to characterise gas giant atmospheres
Space telescopes such as EChO (Exoplanet Characterisation Observatory) and
JWST (James Webb Space Telescope) will be important for the future study of
extrasolar planet atmospheres. Both of these missions are capable of performing
high sensitivity spectroscopic measurements at moderate resolutions in the
visible and infrared, which will allow the characterisation of atmospheric
properties using primary and secondary transit spectroscopy. We use the NEMESIS
radiative transfer and retrieval tool (Irwin et al. 2008, Lee et al. 2012) to
explore the potential of the proposed EChO mission to solve the retrieval
problem for a range of H2-He planets orbiting different stars. We find that
EChO should be capable of retrieving temperature structure to ~200 K precision
and detecting H2O, CO2 and CH4 from a single eclipse measurement for a hot
Jupiter orbiting a Sun-like star and a hot Neptune orbiting an M star, also
providing upper limits on CO and NH3. We provide a table of retrieval
precisions for these quantities in each test case. We expect around 30
Jupiter-sized planets to be observable by EChO; hot Neptunes orbiting M dwarfs
are rarer, but we anticipate observations of at least one similar planet.Comment: 22 pages, 30 figures, 4 tables. Accepted for publication in MNRA
The influence of coronal EUV irradiance on the emission in the He I 10830 A and D3 multiplets
Two of the most attractive spectral windows for spectropolarimetric
investigations of the physical properties of the plasma structures in the solar
chromosphere and corona are the ones provided by the spectral lines of the He I
10830 A and 5876 A (or D3) multiplets, whose polarization signals are sensitive
to the Hanle and Zeeman effects. However, in order to be able to carry out
reliable diagnostics, it is crucial to have a good physical understanding of
the sensitivity of the observed spectral line radiation to the various
competing driving mechanisms. Here we report a series of off-the-limb non-LTE
calculations of the He I D3 and 10830 A emission profiles, focusing our
investigation on their sensitivity to the EUV coronal irradiation and the model
atmosphere used in the calculations. We show in particular that the intensity
ratio of the blue to the red components in the emission profiles of the He I
10830 A multiplet turns out to be a good candidate as a diagnostic tool for the
coronal irradiance. Measurements of this observable as a function of the
distance to the limb and its confrontation with radiative transfer modeling
might give us valuable information on the physical properties of the solar
atmosphere and on the amount of EUV radiation at relevant wavelengths
penetrating the chromosphere from above.Comment: 19 pages, 11 figures (pre-print format). Accepted for publication in
Ap
Inverse scattering of an embedded inhomogeneous dielectric cylinders coated on a conductor
[[abstract]]In this paper, the inverse problem of an embedded inhomogeneous dielectric cylinders coated on a conductor by TM wave illumination is investigated. Inhomogeneous dielectric cylinders coated on a conductor embedded in a slab scatters a group of unrelated incident waves from outside. The scattered field is recorded outside the slab. By proper arrangement of the various unrelated incident field, the difficulties of ill-posedness and nonlinearity are circumvented, and the permittivity distribution can be reconstructed through simple matrix operations. The algorithm is based on the moment method and the unrelated illumination method. Numerical results are given to demonstrate the capability of the inverse algorithm. They also show that the permittivity distribution of the cylinders can be successfully reconstructed even when the permittivity is fairly large. Good reconstructed is obtained even in the presence of additive Gaussian noise in measured data. In addition, the effect of noise on the reconstruction result is also investigated.[[notice]]需補地點及國別[[conferencetype]]國際[[conferencedate]]20060903~2006090
Image reconstruction of inhomogeneous biaxial dielectric cylinders buried in a slab medium
100學年度研究獎補助論文[[abstract]]The image reconstruction of inhomogeneous biaxial dielectric cylinders buried in a slab medium is investigated. A biaxial dielectric cylinder of unknown permittivities buried in a slab scatters a group of unrelated incident waves from outside. The scattered field is recorded outside the slab. By proper arrangement of the various unrelated incident fields, the difficulties of ill-posedness and nonlinearity are circumvented, and the permittivity distribution can be reconstructed through simple matrix operations. The algorithm is based on the moment method and the unrelated illumination method. Numerical results are given to demonstrate the capability of the inverse algorithm. Good reconstructed results are obtained even in the presence of additive Gaussian random noise in measured data. In addition, the effect of noise on the reconstruction result is also investigated.[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙
Electromagnetic Imaging for Inhomogeneous Dielectric Cylinder Buried in a Slab Medium
[[abstract]]The electromagnetic imaging of inhomogeneous dielectric cylinders buried in a slab medium is investigated. Dielectric cylinders of unknown permittivities are buried in second space and scattered a group of unrelated waves incident from first space where the scattered field is recorded. By proper arrangement of the various unrelated incident field, the difficulties of ill-posedness and nonlinearity are circumvented, and the permittivity distribution can be reconstructed through simple matrix operations. The algorithm is based on the moment method and the unrelated illumination method. Numerical results are given to demonstrate the capability of the inverse algorithm. They also show that the permittivity distribution of the cylinders can be successfully reconstructed even when the permittivity is fairly large. Good reconstructed results are obtained even in the presence of additive Gaussian noise in measured data. In addition, the effect of noise on the reconstruction result is also investigated.[[notice]]補正完畢[[incitationindex]]EI[[booktype]]紙
Neutrino tomography
Neutrinos are produced in weak interactions as states with definite flavor—electron, muon, or tau—and these flavor states are superpositions of states of different mass. As a neutrino propagates through space, the different mass eigenstates interfere, resulting in time-dependent flavor oscillation. Though matter is transparent to neutrinos, the flavor oscillation probability is modified when neutrinos travel through matter. Herein, we present an introduction to neutrino propagation through matter in a manner accessible to advanced undergraduate students. As an interesting application, we consider neutrino propagation through matter with a piecewise-constant density profile. This scenario has relevance in neutrino tomography, in which the density profile of matter, like the Earth\u27s interior, can be probed via a broad-spectrum neutrino beam. We provide an idealized example to demonstrate the principle of neutrino tomography
A General Theory of Non-equilibrium Dynamics of Lipid-protein Fluid Membranes
We present a general and systematic theory of non-equilibrium dynamics of
multi-component fluid membranes, in general, and membranes containing
transmembrane proteins, in particular. Developed based on a minimal number of
principles of statistical physics and designed to be a meso/macroscopic-scale
effective description, the theory is formulated in terms of a set of equations
of hydrodynamics and linear constitutive relations. As a particular emphasis of
the theory, the equations and the constitutive relations address both the
thermodynamic and the hydrodynamic consequences of the unconventional material
characteristics of lipid-protein membranes and contain proposals as well as
predictions which have not yet been made in already existed work on membrane
hydrodynamics and which may have experimental relevance. The framework
structure of the theory makes possible its applications to a range of
non-equilibrium phenomena in a range of membrane systems, as discussions in the
paper of a few limit cases demonstrate.Comment: 22 pages, 2 figures, minor changes and addition
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