scholarly journals Modeling the Infrared Magnesium and Hydrogen Lines from Quiet and Active Solar Regions

1994 ◽  
Vol 154 ◽  
pp. 323-339
Author(s):  
E. H. Avrett ◽  
E. S. Chang ◽  
R. Loeser
Keyword(s):  
Cross Sections ◽  
Line Emission ◽  
Atmospheric Model ◽  
Atmospheric Temperature ◽  
Atomic Data ◽  
Atmospheric Models ◽  
Spatial Features ◽  
Highly Sensitive ◽  
Hydrogen Lines ◽  
The Continuum

The emission lines of Mg I at 7.4, 12.2, and 12.3 μm are now known to be formed in the upper photosphere; the line emission is due to collisional coupling of higher levels with the continuum together with radiative depopulation of lower levels. These combined effects cause the line source functions of high-lying transitions to exceed the corresponding Planck functions. However, there are uncertainties in a) the relevant atomic data, particularly the collisional rates and ultraviolet photoionization rates, and b) the sensitivity of the calculated results to changes in atmospheric temperature and density. These uncertainties are examined by comparing twelve calculated Mg I line profiles in the range 2.1-12.3 μm with ATMOS satellite observations. We show results based on different rates, and using different atmospheric models representing a range of dark and bright spatial features. The calculated Mg profiles are found to be relatively insensitive to atmospheric model changes, and to depend critically on the choice of collisional and photoionization rates. We find better agreement with the observations using collision rates from van Regemorter (1962) rather than from Seaton (1962). We also compare twelve calculated hydrogen profiles in the range 2.2-12.4 μm with ATMOS observations. The available rates and cross sections for hydrogen seem adequate to account for the observed profiles, while the calculated lines are highly sensitive to atmospheric model changes. These lines are perhaps the best available diagnostics of the temperature and density structure of the photosphere and low chromosphere. Further calculations based on these infrared hydrogen lines should lead to greatly improved models of the solar atmosphere.

A comparison of the microphysics dependency on the reproducibility of the MJO under different resolutions using NICAM

2021 ◽  
Author(s):  
Tamaki Suematsu ◽  
Yohei Yamada ◽  
Chihiro Kodama ◽  
Tomoki Miyakawa
Keyword(s):  
General Circulation ◽  
Atmospheric Model ◽  
Cloud Microphysics ◽  
Horizontal Resolution ◽  
Madden Julian Oscillation ◽  
Atmospheric Models ◽  
Highly Sensitive ◽  
Resolution Model ◽  
Intercomparison Project ◽  
High Resolution Model

<p>Simulation of the Madden-Julian Oscillation (MJO) has been notoriously difficult in atmospheric models. This is partly due to the fact that the reproducibility of the MJO is highly sensitive to parameters that are difficult to fix from observation or theory, and require empirical tuning based on model behaviors. Parameters regards to the cloud-microphysics are some of such parameters that simulations of the MJO are especially sensitive to.</p><p>To address this problem, we conducted a set of cloud-microphysics parameter-sweep experiments on a convection-permitting model, NICAM (Nonhydrostatic ICosahedral Atmospheric Model) at 14 km horizontal resolution to seek for a setting which best represents the MJO (MJO-tuned). We then compared the performance of the NICAM in reproducing the MJO using MJO-tuned setting with the standard NICAM setting employed for high resolution model intercomparison project (High Res MIP)-type experiments. The comparison was conducted for 14 km resolution, and for 3.5 km resolution experiments using DYAMOND (DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains) data, which is based on the MJO-tuned setting.</p><p>The comparison indicated that in the 14 km resolutions, the MJO-tuned setting reduces the excessive development of convection over the Maritime Continents which was apparent in the High Res MIP-setting. However, for the 3.5 km experiments convective activities of the MJO appeared to successfully reach the dateline for both the MJO-tuned setting and the High Res MIP-setting. The results of this study implies that a sufficient increase in the horizontal resolution has the potential to reduce the dependency of the microphysics setting on the reproducibility of the MJO, at least in the first few weeks of the simulations on NICAM.</p>

A PANORAMA OF CDCC CALCULATIONS FOR DEUTERON INDUCED REACTIONS: FROM ELASTIC CROSS SECTIONS TO INELASTIC AND TRANSFER ONES

2011 ◽  
Vol 20 (04) ◽  
pp. 953-957 ◽  
Author(s):  
P. HUU-TAI CHAU
Keyword(s):  
Experimental Data ◽  
Cross Sections ◽  
Deformed Nuclei ◽  
Coupled Channels ◽  
The Continuum

An overview of calculations performed within the Continuum Discretized Coupled Channels (CDCC) approach for deuteron induced reactions is given. We briefly present an extension of the CDCC formalism which accounts for the target excitations allowing us to determine ( d , d ') cross sections off deformed nuclei. We compare some calculated inelastic cross sections with experimental data. Then it is shown that the CDCC formalism can also be a useful tool to determine ( d , p ) cross sections. This point is illustrated with 54 Cr ( d , p )55 Cr reactions.

scholarly journals Water maser and radio continuum emission towards IRAS 23139+5939

2007 ◽  
Vol 3 (S242) ◽  
pp. 180-181
Author(s):  
M. A. Trinidad ◽  
S. Curiel ◽  
J. M. Torrelles ◽  
L. F. Rodríguez ◽  
V. Migenes ◽  
...  
Keyword(s):  
Flux Density ◽  
Line Emission ◽  
The Other ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Maser Line ◽  
Water Masers ◽  
Water Maser ◽  
The Continuum

AbstractWe present simultaneous observations of continuum (3.5 and 1.3cm) and water maser line emission (1.3cm) carried out with the VLA-A toward the high-mass object IRAS 23139+5939. We detected two radio continuum sources at 3.5cm separated by 0”5 (~2400 AU), I23139 and I23139S. Based on the observed continuum flux density and the spectral index, we suggest that I23139 is a thermal radio jet associated with a high-mass YSO. On the other hand, based on the spatio-kinematical distribution of the water masers, together with the continuum emission information, we speculate that I23139S is also a jet source powering some of the masers detected in the region.

scholarly journals ESTUDO AVALIATIVO DA PREVISÃO NUMÉRICA DO TEMPO DE CURTO PRAZO PARA O MUNICÍPIO DE MACEIÓ/AL, UTILIZANDO O MODELO WRF

2020 ◽  
Vol 12 (6) ◽  
pp. 2121
Author(s):  
Rosiberto Salustiano Silva Junior ◽  
Bruno César Teixeira Cardoso ◽  
Hugo Cainã Ferreira Monteiro ◽  
Ewerton Hallan de Lima Silva
Keyword(s):  
Weather Forecast ◽  
Atmospheric Model ◽  
Weather Research And Forecasting ◽  
Atmospheric Models ◽  
Economic Activities ◽  
Land User ◽  
The City ◽  
Model Topography ◽  
Better Than ◽  
Weather Research

Sendo as diferentes atividades econômicas fortemente influenciadas pela condição do tempo, faz-se necessário antever com dias de antecedência a situação meteorológica favorável ou não para o cotidiano da sociedade. E os modelos atmosféricos são ferramentas amplamente utilizados para avaliar o estado futuro da atmosfera, neste contexto, avaliar a precisão das previsões realizadas por estas ferramentas, tem sido cada fez mais recorrente. Neste trabalho foi utilizado o modelo atmosférico WRF (Weather Research and Forecasting) para realizar previsões diárias com duração de 72h, durante o período de 10 a 19 de julho de 2017 para a cidade de Maceió/AL. Para validar as previsões foram utilizados os dados observados da estação meteorológica automática do INMET (Instituto Nacional de Meteorologia). Para este estudo também foi proposto a atualização da topografia e uso do solo da área de estudo em questão, que gerou melhorias nas comparações realizadas para todas as variáveis analisadas, em destaque a previsão da variável pressão atmosférica, quando atualizada a topografia houve sensíveis melhorias nos indicadores estatísticos em comparação aos demais testes que não contaram com mesma atualização. Além disso, as análises estatísticas e os gráficos apresentados comprovam que o modelo previu melhor para 24h do que para 48h e nesta sequência melhor que 72h, ou seja, existiu a depreciação das previsões com o aumento da duração das previsões. Study of the Efficiency of the Short-Term Numerical Forecast for the City of Maceió / Al, Using the WRF ModelA B S T R A C TThe different economic activities are strongly influenced by the condition of the weather, it is necessary to forecast with days in advance the meteorological situation favorable or not for the daily life of the society. The atmospheric models are tools widely used to assess the future state of the atmosphere, in this context, assess the accuracy of the forecasts made by these tools, has been each made more recurrent. In this work the atmospheric model WRF (Weather Research and Forecasting) was used to make daily forecasts with a duration of 72h during the period from July 10 to 19, 2017 for the city of Maceió / AL, to validate the forecasts were used the observed data of the INMET (National Meteorological Institute) automatic weather station. For this study it was also proposed to update the topography and land user of the study area, which generated improvements in the comparisons made for all variables analyzed, in particular the prediction of the variable atmospheric pressure, when updated the topography there were sensible improvements in statistical indicators compared to the other tests that did not have the same update. In addition, the statistical analyzes and the graphs presented show that the model predicted better for 24h than for 48h and in this sequence better than 72h, that is, there was depreciation of the forecasts with the increase of the forecast duration.Keywords: Weather Forecast, Atmospheric Model, Topography, Land User.

Transient Light Emissions from a Laser Perturbed Plasma

1972 ◽  
Vol 50 (19) ◽  
pp. 2338-2347 ◽  
Author(s):  
H. A. Baldis ◽  
R. A. Nodwell ◽  
J. Meyer
Keyword(s):  
Laser Pulse ◽  
Electron Density ◽  
Laser Light ◽  
Line Emission ◽  
Argon Plasma ◽  
Stark Broadening ◽  
Excited Atoms ◽  
Electron Density Gradient ◽  
Transient Plasma ◽  
The Continuum

The interaction between a 20 MW Q-switched ruby laser pulse and a partially ionized argon plasma has been studied experimentally. When the focused laser pulse is fired into the plasma, a transient emission from the plasma may be observed both in the continuum and line emission. From measurements of the absolute intensities of this transient radiation, estimates have been made of the population density of the excited atoms and of the electron densities. The Stark broadening of the Ar II lines has also been measured to obtain the electron density in the transient plasma and data obtained in this way are consistent with those obtained from the continuum radiation. During the time when the laser light is incident on the plasma the Ar II lines show a strong asymmetry which disappears quickly after the laser pulse has terminated. This asymmetry can be explained in terms of the electron density gradient present in the expanding perturbed plasma.

scholarly journals Spectropolarimetric monitoring of WR140

1995 ◽  
Vol 163 ◽  
pp. 506-507
Author(s):  
R.E. Schulte-Ladbeck ◽  
K. H. Nordsieck ◽  
K. S. Bjorkman ◽  
M. R. Meade ◽  
B. L. Babler
Keyword(s):  
Detection Limit ◽  
Linear Polarization ◽  
Broad Band ◽  
Line Emission ◽  
Intrinsic Polarization ◽  
The Continuum

We report on eight years of spectropolarimetric monitoring of the WR140 binary. The broad-band linear polarization decreased systematically after the 1985 periastron passage. By 1991, it settled to a constant value at which it has remained through the 1993 periastron passage. We do not detect, in data taken after 1989, a line-effect in He II Λ4686. This suggests either that the continuum and the line emission scatter at the same region, or that any intrinsic polarization has been below our detection limit. We conclude that the presently observed polarization of WR140 is consistent with interstellar foreground polarization.

scholarly journals 12-μM Observations at the 1991 Eclipse

1994 ◽  
Vol 154 ◽  
pp. 151-160
Author(s):  
D. E. Jennings ◽  
D. Deming ◽  
G. Mccabe ◽  
R. Noyes ◽  
G. Wiedemann ◽  
...  
Keyword(s):  
Line Emission ◽  
Emission Feature ◽  
Hydrostatic Equilibrium ◽  
Infrared Telescope ◽  
Model Predictions ◽  
Theoretical Predictions ◽  
Telescope Facility ◽  
Density Inhomogeneities ◽  
Infrared Telescope Facility ◽  
The Continuum

The 11 July 1991 total solar eclipse over Mauna Kea was a unique opportunity to study the limb profile of the 12.32 μm MgI emission line. Our observations used the NASA 3-meter Infrared Telescope Facility,1 and a new Goddard large cryogenic grating spectrometer. Spectra of the line were taken in the slitless mode at second contact. The results show that the emission peaks within ~ 300 km of the 12-μm continuum limb. This agrees with recent theoretical predictions for this line as a NLTE upper photospheric emission feature. However, the increase in optical depth for this extreme limb-viewing situation means that most of the observed emission arises from above Tmin, and we find that this emission is extended to altitudes well in excess of the model predictions. The line emission can be traced to altitudes as high as 2000 km above the 12-μm continuum limb, whereas theory predicts it to remain observable no higher than 500 km above the continuum limb. The substantial limb-extension observed in this line is qualitatively consistent with limb-extensions seen by other observers in the far-IR continuum, and may be indicative of departures from gravitational hydrostatic equilibrium in the upper solar atmosphere, and/or may result from temperature and density inhomogeneities. The extended altitude of formation of this line enhances its value as a Zeeman probe of magnetic fields.

scholarly journals O and Of Stars

1973 ◽  
Vol 49 ◽  
pp. 93-107
Author(s):  
Peter S. Conti
Keyword(s):  
Visible Spectrum ◽  
Emission Lines ◽  
Absorption Lines ◽  
Evolutionary Status ◽  
Be Stars ◽  
Type B ◽  
No Emission ◽  
Hot Stars ◽  
Hydrogen Lines ◽  
The Continuum

My intention here is to discuss the ‘high temperature’ portion of this symposium and call attention to those stars that are called Of. There are some similarities in spectral appearance to WR stars, e.g. emission lines. I should first like to define what I think are the essential differences among four groups of hot stars;O stars: Stars that have only absorption lines in the visible spectrum. Type O is distinguished from type B by the presence of He ii 4541 at MK dispersion. It may be that some (supergiants) O stars will have emission lines in the rocket UV region but this description will be primarily concerned with ground based observations.Of stars: These are O type stars that also have λλ 4634,40 N iii in emission above the continuum. In addition to normal O star absorption lines and N iii emission, they may also have other lines in emission. I will discuss this further below.Oe stars: These are O type stars that have emission in the hydrogen lines (or at least at Hα), but with no emission in N iii or in other lines. I personally think that this small class of objects is related to the Be stars in their evolutionary status and in their emission mechanism.WR stars: These stars are primarily characterized by emission lines. The only absorption lines seen are violet shifted (P Cyg type). Although in some cases emission lines appear which are similar to those found in some Of stars, the latter types always have some unshifted absorption lines present. Several Of stars have P Cyg profiles in some lines.

COUPLED-CHANNELS ANALYSES OF 6He BREAKUP REACTIONS

2009 ◽  
Vol 24 (11) ◽  
pp. 2191-2197 ◽  
Author(s):  
T. MATSUMOTO ◽  
T. EGAMI ◽  
K. OGATA ◽  
Y. ISERI ◽  
M. KAMIMURA ◽  
...  
Keyword(s):  
Cross Sections ◽  
Reaction System ◽  
Basis Functions ◽  
Coulomb Breakup ◽  
Body Model ◽  
Coupled Channels ◽  
Gaussian Basis Functions ◽  
Three Body ◽  
Good Agreement ◽  
The Continuum

We present analyses of breakup effects of 6 He on the elastic scattering by the continuum-discretized coupled-channels method, in which the reaction system is described as a four-body model, n+n+4 He +target. In this analysis, three-body breakup continuum of 6 He is discretized by daiagonalizing the internal Hamiltonian of 6 He in a space spanned by the Gaussian basis functions. The calculated elastic cross sections are in good agreement with the experimental data, which shows that nuclear and Coulomb breakup effects are significant.

Photoelectric cross sections derived from the total absorption cross sections in the energy range 5–130 keV

1979 ◽  
Vol 57 (1) ◽  
pp. 92-98 ◽  
Author(s):  
K. S. Puttaswamy ◽  
Ramakrishna Gowda ◽  
B. Sanjeevaiah
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Proportional Counter ◽  
Atomic Data ◽  
Total Absorption ◽  
Absorption Cross ◽  
Total Cross Sections ◽  
Scattering Cross ◽  
Data Tables ◽  
Scattering Cross Sections

Total absorption cross sections in the elements C, Al, S, Cu, Zr, Ag, Sn, Ta, Au, and Pb for photons of energies 5.0, 5.9, 6.4, 8.1, 10.6, 14.4, 24.7, 32.9, 36.9, 66.6, and 129 keV are measured using a krypton-filled proportional counter in the energy range 5 to 25 keV and a thin NaI(Tl) detector in the energy range 30 to 130 keV. The measured total absorption cross sections are compared with those of Miller and Greening and McCrary, Plassman, Paekett, Conner, and Zimmermann. The scattering cross sections obtained by interpolation using the Atomic Data Tables are subtracted from the total cross sections to obtain the photoelectric cross sections and these are further compared with the recent theoretical values of Scofield.

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