The global oscillation network group site survey

Hill, F.; Fischer, George R.; Grier, J. A.; Leibacher, J. W.; Jones, H. P.; Jones, Patricia P.; Kupke, Renate; Stebbins, R. T.

doi:10.1007/bf00680443

Cited by 40 publications

(22 citation statements)

References 16 publications

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“…The selection procedure of Oukaïmeden as a potential site for astronomical observations was presented by Benkhaldoun et al (1991) and Benkhaldoun (1994). The studies of photometric and meteorological qualification were also treated in several publications: Benkhaldoun, Kadiri & Vernin (1993), Hill et al (1994a,b), Jabiri et al (2000), Benkhaldoun (2002) and Benkhaldoun et al (2005). Measurements of seeing were also carried out by the Generalized Seeing Monitor (GSM) instrument but over a very short period, 1 and the results of this campaign were published by Ziad et al (2001).…”

Section: Introductionmentioning

confidence: 99%

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Hach¹,

Jabiri²,

Ziad³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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In this paper, we have used the National Centers for Environmental Prediction (NCEP)/National Centers for Atmospheric Research (NCAR) Reanalysis data base to study, first, a comparison between balloon sounding made at different stations with coinciding model‐based meteorological analysis. The comparison allows the assessment of reliability of the analysis in the studied period and to highlight NCEP/NCAR Reanalysis as an interesting data base for site characterization. Using the same system of Reanalysis, we present, secondly, the first complete characterization of main meteorological parameters at Oukaïmeden Observatory: wind speed, its direction, temperature and pressure. The statistical treatment of data will cover the years between 1990 and 2009. Monthly, seasonal and annual results are analysed. The comprehensive and reliable statistics of tropospheric wind speeds at Oukaïmeden are presented. We found a clear annual periodicity of 200 mbar wind speed. This periodicity could be related to the seasonal dependence of seeing that is affected by the existence of cloud sea during the period around autumn–winter and by high wind speed regimes during spring. The connection of high‐ to low‐altitude tropospheric winds has been explored. We found a high correlation comparable to the ones found at La Silla and La Palma sites. The local parameters in particular topography and stratocumulus formations might affect 700 mbar wind roses. Richardson numbers calculated for each month at Oukaïmeden and La Palma are presented. By analysing the values, we found out that the periods and the regions of development of turbulence in relative terms of stability for the two locations are very similar. In addition, we present the first example of a profile estimated from NCEP/NCAR Reanalysis. We found that this profile presents a tendency very similar to the same averaged profile measured by the balloon‐born radiosondes.

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Section: Introductionmentioning

confidence: 99%

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Hach¹,

Jabiri²,

Ziad³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…Effectively the extraction of the internal radial sound speed from a great number of acoustic modes determined by ground networks GONG (Hill et al 1994(Hill et al , 1996, IRIS (Grec et al 1991, BiSON (Elsworth et al 1994, Chaplin et al 1996a and LOWL (Tomczyk et al 1995), has allowed the determination of the base of the convection zone ( r bcz = 0.713 ± 0.003R ⊙ : Christensen-Dalsgaard, Thompson 1991, Basu andAntia 1997), the verification of the equation of state for light elements, with the precise determination of photospheric helium content Y ph = 0.249 ± 0.003 ( Vorontsov, Baturin andPamyatnykh 1992, Basu andAntia 1995), thus compelling the introduction of the slow microscopic diffusion process.…”

Section: Introductionmentioning

confidence: 99%

Standard Solar Models in the Light of New Helioseismic Constraints. I. The Solar Core

Brun

Turck‐Chièze

Morel

1998

ApJ

131

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In this paper, we examine a new, updated solar model that takes advantage of the recent reexamination of nuclear reaction rates and the microscopic di †usion of helium and heavy elements. Our best model Ðts the helioseismic data reasonably well, giving the base of the convective zone at R bcz \ 0.715, the photospheric helium in mass fraction as 0.243, and the sound-speed square di †erence between the Sun and the model as dc2/c2 \ 1%. This model leads to a reestimate of neutrino Ñuxes, giving 7.18 SNU for the chlorine experiment, 127.2 SNU for the gallium detector, and 4.82 106 cm~2 s~1 for the 8B neutrino Ñux. Acoustic-mode predictions are also estimated. We then consider the radiative zone and discuss what we learn from such a model when confronted with the present helioseismic constraints from space experiments aboard SOHO. We present three models that respect these constraints and better Ðt the seismic observations by taking advantage of the known physical uncertaintiesÈnuclear reaction rates, CNO abundances, and microscopic di †usion. We also study some current questions, such as the possibility of mixing in the nuclear core, the revision of the solar radius, and the inÑuence of the solar age. We conclude that the standard model, inside its inherent uncertainties, is robust in light of the present acoustic-mode detection and that mixing in the core is not really favored, even though a proper understanding of the angular momentum evolution with time has not yet been reached. The initial solar helium abundance seems more and more constrained ; this study supports an initial abundance between 0.273 and 0.277 in mass fraction. This analysis allows us to deÐne minimal values for neutrino predictions, compatible with present seismic results. We note that a reduction of about 30% in chlorine and water detectors, which is more than half the discrepancy with the experimental results, is still supported by the present study. This work also emphasizes the fact that acoustic-mode determination does not put strong constraints on the nuclear plasma characteristics. Finally, we estimate g-mode frequencies in a range that may be accessible to the satellite SOHO ; these results emphasize the substantially improved sensitivity of these modes to details of the nuclear solar core, and show the frequency dependence of these modes for the di †erent models previously discussed.

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“…To put the observations in context, we have made use of data provided by some of the band-pass filters (AIA; Lemen et al 2012) on board NASA's Solar Dynamics Observatory (SDO; Pesnell et al 2012), by the Global Oscillation Network Group (GONG; Hill et al 1994) and from the Chromospheric Telescope (Chrotel; Bethge et al 2011). We display in Fig.…”

Section: Solar Contextmentioning

confidence: 99%

Diagnostic potential of the Ca II 8542 Å line for solar filaments

Baso

González

Ramos

et al. 2019

A&A

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Aims. In this study we explore the diagnostic potential of the chromospheric Ca ii line at 8542 Å for studying the magnetic and dynamic properties of solar filaments. We have acquired high spatial resolution spectropolarimetric observations in the Ca ii 8542 Å line using the CRISP instrument at the Swedish 1-m Solar Telescope. Methods. We use the NICOLE inversion code to infer physical properties from observations of a solar filament. We discuss the validity of the results due to the assumption of hydrostatic equilibrium. We have used observations from other telescopes such as Chrotel and SDO, in order to study large scale dynamics and the long term evolution of the filament. Results. We show that the Ca ii 8542 Å line encodes information of the temperature, line-of-sight velocity and magnetic field vector from the region where the filament is located. The current noise level only allow us to estimate an upper limit of 260 G for the total magnetic field of the filament. Our study also reveals that if we only consider information from the aforementioned spectral line, the geometric height, the temperature and the density can be degenerated parameters outside the hydrostatic equilibrium approach.

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The global oscillation network group site survey

Cited by 40 publications

References 16 publications

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Standard Solar Models in the Light of New Helioseismic Constraints. I. The Solar Core

Diagnostic potential of the Ca II 8542 Å line for solar filaments

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The global oscillation network group site survey

Cited by 40 publications

References 16 publications

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

Standard Solar Models in the Light of New Helioseismic Constraints. I. The Solar Core

Diagnostic potential of the Ca II 8542 Å line for solar filaments

Contact Info

Product

Resources

About

Diagnostic potential of the Ca II 8542 Å line for solar filaments