The Interpretation of EUV Spectra of Sunspots

1983 ◽  
Vol 71 ◽  
pp. 325-326
Author(s):  
J.G. Doyle ◽  
J.C. Raymond ◽  
R.W. Noyes ◽  
A.E. Kingston
Keyword(s):  
Observational Data ◽  
Electron Density ◽  
Constant Pressure ◽  
Wavelength Region ◽  
Constant Density ◽  
Ionization Equilibrium ◽  
Sensitive Line ◽  
Temperature Diagnostic

We report here on EUV observations of a sunspot observed by the Harvard instrument on Skylab. The observational data used here have been presented in a previous paper by Noyes et al. (1982), in which line identifications and intensities for the wavelength region 350 – 1350 A were given. Several electron density sensitive line ratios suggest a constant density, rather than constant pressure, emitting region, while temperature diagnostic line ratios of several ions yield temperatures below the temperatures expected in ionization equilibrium.

FIRST SOUND IN LIQUID HELIUM AT HIGH PRESSURES

1953 ◽  
Vol 31 (7) ◽  
pp. 1156-1164 ◽  
Author(s):  
K. R. Atkins ◽  
R. A. Stasior
Keyword(s):  
Specific Heat ◽  
Liquid Helium ◽  
Carrier Frequency ◽  
High Pressures ◽  
Constant Pressure ◽  
Constant Density ◽  
Pulse Technique ◽  
Temperature Range ◽  
Specific Heats ◽  
First Sound

The velocity of ordinary sound in liquid helium has been measured in the temperature range from 1.2 °K. to 4.2 °K. at pressures up to 69 atm. A pulse technique was used with a carrier frequency of 12 Mc.p.s. Curves are given for the variation of velocity with temperature at constant pressure and also at constant density. There is no detectable discontinuity along the λ-curve. The results are used to discuss the ratio of the specific heats, the coefficient of expansion below 0.6 °K., and the specific heat above 3 °K.

Shocks

2018 ◽  
Author(s):  
S. G. Rajeev
Keyword(s):  
Burgers Equation ◽  
Constant Pressure ◽  
Initial Density ◽  
One Dimension ◽  
Constant Density ◽  
Problem Of Time ◽  
Small Viscosity ◽  
Maxwell Construction ◽  
Zero Viscosity ◽  
Basic Intuition

When the speed of a fluid exceeds that of sound, discontinuities in density occur, called shocks.The opposite limit from incompressibility (constant density) is constant pressure. In this limit, we get Burgers equation. It can be solved exactly in one dimension using the Cole–Hopf transformation. The limit of small viscosity is found not to be the same as zero viscosity: there is a residual drag no matter how small it is. The Maxwell construction of thermodynamics was adapted by Lax and Oleneik to derive rules for shocks in this limit. The Riemann problem of time evolution with a discontinuous initial density is solved in one dimension. These simple solutions provide the basic intuition for more complicated shocks.

scholarly journals Solar EUV Rocket Telescope and Spectrograph (SERTS) Observations of Fe XII Emission Lines

1996 ◽  
Vol 152 ◽  
pp. 531-536
Author(s):  
F.P. Keenan ◽  
R.J. Thomas ◽  
W.M. Neupert ◽  
V.J. Foster ◽  
C.J. Greer ◽  
...  
Keyword(s):  
Active Region ◽  
Emission Line ◽  
Electron Temperature ◽  
Observational Data ◽  
Electron Density ◽  
Wavelength Range ◽  
Solar Spectrum ◽  
Emission Lines ◽  
First Time ◽  
Good Agreement

Abstract.Theoretical electron density sensitive emission line ratios involving transitions in the 186–383 Å wavelength range are compared with observational data for a solar active region and a subflare, obtained by the Solar EUV Rocket Telescope and Spectrograph (SERTS). Electron densities derived from the majority of the ratios are consistent with one another, and are also in good agreement with the values of density estimated from diagnostic lines in other species formed at similar temperatures to Fe XII. These results provide observational support for the general accuracy of the diagnostic calculations. In addition, our analysis indicates that a line at 283.70 Å in the active region spectrum is the 3s23p32D3/2−3s3p42P1/2 transition in Fe XII, the first time (to the best of our knowledge) that this line has been identified in the solar spectrum. Several of the line ratios considered are predicted to be relatively insensitive to the adopted electron temperature and density, and the generally good agreement found between theory and observation for these provides evidence for the reliability of the SERTS instrument calibration. The application of the Fe XII diagnostics to EUVE observations of the F5 subgiant Procyon is briefly discussed.

EUV Line Diagnostics for CDS and Sumer on SOHO

1994 ◽  
Vol 144 ◽  
pp. 625-630
Author(s):  
B. N. Dwivedi
Keyword(s):  
Active Region ◽  
Electron Density ◽  
Line Ratio ◽  
Theoretical Curve ◽  
Line Intensities ◽  
Sensitive Line ◽  
Electron Density And Temperature

AbstractThe EUV line diagnostics for the CDS and the SUMER instruments, to be flown onboard the SOHO mission, are discussed. Serts observations of EUV line intensities in an active region, reported by Thomas and Neupert (1993), have been used to determine the electron density and temperature from a theoretical curve of Mg VIII density-sensitive line ratio.

scholarly journals Electron-density-sensitive Line Ratios of Fe xiii– xvi from Laboratory Sources Compared to CHIANTI

2018 ◽  
Vol 854 (2) ◽  
pp. 102 ◽  
Author(s):  
M. E. Weller ◽  
P. Beiersdorfer ◽  
V. A. Soukhanovskii ◽  
F. Scotti ◽  
B. P. LeBlanc
Keyword(s):  
Electron Density ◽  
Sensitive Line

scholarly journals A new global model for the ionospheric F2 peak height for radio wave propagation

2012 ◽  
Vol 30 (5) ◽  
pp. 797-809 ◽  
Author(s):  
M. M. Hoque ◽  
N. Jakowski
Keyword(s):  
Observational Data ◽  
Electron Density ◽  
Temporal Variations ◽  
Global Scale ◽  
Peak Height ◽  
Frequency Planning ◽  
Spatial Dependencies ◽  
Planning And Operation ◽  
Height Model ◽  
Model Approach

Abstract. The F2-layer peak density height hmF2 is one of the most important ionospheric parameters characterizing HF propagation conditions. Therefore, the ability to model and predict the spatial and temporal variations of the peak electron density height is of great use for both ionospheric research and radio frequency planning and operation. For global hmF2 modelling we present a nonlinear model approach with 13 model coefficients and a few empirically fixed parameters. The model approach describes the temporal and spatial dependencies of hmF2 on global scale. For determining the 13 model coefficients, we apply this model approach to a large quantity of global hmF2 observational data obtained from GNSS radio occultation measurements onboard CHAMP, GRACE and COSMIC satellites and data from 69 worldwide ionosonde stations. We have found that the model fits to these input data with the same root mean squared (RMS) and standard deviations of 10%. In comparison with the electron density NeQuick model, the proposed Neustrelitz global hmF2 model (Neustrelitz Peak Height Model – NPHM) shows percentage RMS deviations of about 13% and 12% from the observational data during high and low solar activity conditions, respectively, whereas the corresponding deviations for the NeQuick model are found 18% and 16%, respectively.

Properties of a Lattice Gas Model for 3He–4He Mixtures II: Analysis of High Temperature Series for the f.c.c. Lattice

1975 ◽  
Vol 53 (10) ◽  
pp. 987-1002 ◽  
Author(s):  
M. Plischke ◽  
D. D. Betts
Keyword(s):  
High Temperature ◽  
Specific Heat ◽  
Lattice Gas ◽  
Chemical Potential ◽  
Constant Pressure ◽  
Temperature Series ◽  
Adjustable Parameter ◽  
Constant Density ◽  
Constant Concentration ◽  
Chemical Potential Difference

For the Cheng–Schick model of 3He–4He mixtures high temperature series expansions at (a) constant density and constant concentration and (b) constant pressure and constant chemical potential difference are presented for the f.c.c. lattice for the fluctuation in the superfluid order parameter, the concentration susceptibility, and the specific heat at constant chemical potential. Analysis of the fluctuation series yields well defined lambda temperatures. In addition analysis of the concentration susceptibility series provides a less precise estimate of the tricritical concentration. The specific heat series have not proved very amenable to analysis. Upon fixing a single adjustable parameter the lambda curve of the model agrees precisely with experiment for all 3He concentrations. Estimates of tricritical exponents could not be obtained.

scholarly journals Heat Flow Birefringence in Liquids and Liquid Crystals

1985 ◽  
Vol 40 (1) ◽  
pp. 3-7
Author(s):  
D. R. Baalss ◽  
S. Hess
Keyword(s):  
Heat Flow ◽  
Constant Pressure ◽  
Planck Equation ◽  
Pressure Variation ◽  
Flow Birefringence ◽  
Isotropic Phase ◽  
Constant Density ◽  
Collision Term ◽  
Nonspherical Particles ◽  
Physical Mechanisms

The alignment of nonspherical particles is inferred from the solution of a Fokker-Planck equation where a thermal torque has been taken into account which is proportional to the second spatial derivative of the temperature field. A pretransitional enhancement of the effect is predicted for the isotropic phase of a liquid crystal. Two distinct physical mechanisms are considered in order to estimate the magnitude of the thermal torque. One of them is due to the pressure variation at constant density. For constant pressure, the torque is inferred from the collision term of an Enskog-Boltzmann equation generalized to (strongly) nonspherical particles. In both cases, the resulting heat flow birefringence is of measurable size.

Electron density sensitive line ratios for Fe XVIII in tokamak plasmas

1987 ◽  
Vol 122 (3-4) ◽  
pp. 170-172 ◽  
Author(s):  
F.P. Keenan ◽  
M. Mohan ◽  
K.L. Baluja ◽  
K.A. Berrington ◽  
A. Hibbert
Keyword(s):  
Electron Density ◽  
Tokamak Plasmas ◽  
Sensitive Line
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