GOLF
Global Oscillations at Low Frequency

GOLF

 

Global Oscillations at Low Frequency

 

GOLF (Global Oscillations at Low Frequencies) est une expérience d'héliosismologie franco-espagnole qui mesure les modes d'oscillations du Soleil en observant l'étoile globalement. Ce spectromètre à résonance mesure en fait la vitesse Doppler entre le satellite et le Soleil dans la raie d'absorption du sodium. Nous détectons ainsi les modes les plus pénétrants: modes radiaux, monopolaires et dipolaires... Ces modes sont riches d'information sur la région nucléaire du Soleil. Cet instrument a pour objectif de tester la modélisation stellaire dans la première phase d'évolution en y introduisant des phénomènes dynamiques absents de l'évolution stellaire classique.

 

Sismologie : généralités
Objectifs scientifiques
Principe de fonctionnement
Caractéristiques et performances
Autres informations : statut, collaborations...
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Download the GOLF data

The GOLF velocity time series were obtained following Garcia et al. (2005). Download the GOLF data from April 11, 1996 to December 31, 2013 below. Data from both PMs (PM1 and PM2) are available, as well as the mean of the two PMs. The temporal cadence of the time series is of 60 seconds and the starting date on April 11, 1996. The duty cycle is of 96%.

Please cite Garcia et al. (2005) when publishing results using these data.

Also use the following in your acknowledgements in publication: "The GOLF instrument onboard SoHO is a cooperative effort of scientists, engineers, and technicians, to whom we are indebted. SoHO is a project of international collaboration between ESA and NASA."

 

Download the GOLF frequencies

The GOLF frequencies provided here are part of the online material of the paper Salabert et al. (2015). They were extracted from one-year (365 days) GOLF time series, with a four-time overlap (91.25 days). A total of 69 non-independent one-year frequency tables covering 18 years of GOLF observations are then available below. The zipped ascii files contain [radial order, angular degree, frequency in μHz, error_on_frequency in μHz]. It contains as well an .info file with:

- column 1: the series index associated to the frequency table;

- column 2: the Julian Date of the starting date of each 365-day time series;

- column 3: the associated duty cycle in %;

- column 4: the corresponding radio flux averaged over the same 365-day periods.

Please cite Garcia et al. (2005) and Salabert et al. (2015) when publishing results using these data.

Also use the following in your acknowledgements in publication: "The GOLF instrument onboard SoHO is a cooperative effort of scientists, engineers, and technicians, to whom we are indebted. SoHO is a project of international collaboration between ESA and NASA."

 

Download the GOLF frequency shifts

The GOLF frequency shifts provided here were obtained and analyzed in Salabert et al. (2015). They were extracted from one-year (365 days) GOLF time series, with a four-time overlap (91.25 days). They were calculated for 4 different frequency ranges: [1800-3790μHz]; the low-frequency range [1800-2450μHz]; the mid-frequency range [2450-3110μHz]; and the high-frequency range [3110-3790μHz]. Oscillation modes from each frequency range are sensitive to different layers in the solar sub-surface interior. The frequency shifts of modes at individual angular degree l=0, l=1, and l=2 are provided, as well as the mean frequency shifts for . We note that we did not use the l=3 mode because of its lower signal-to-noise ratio over most of the oscillation frequency range. However, we provide in the corresponding table the l=3 frequency shifts for the range [2450-3110muHz] as their SNR is sufficient enough to give realiable results.

The zipped ascii files contain

[year, month, day, fshift_l0, e_fshift_l0, fshift_l1, e_fshift_l1, fshift_l2, e_fshift_l2 {, fshift_l3, e_fshift_l3}, radio_flux].

The frequency shifts and their 1σ uncertainties are given in nHz.

Please Salabert et al. (2015) when publishing results using these data, and the following acknowledgements: "The GOLF instrument onboard SoHO is a cooperative effort of scientists, engineers, and technicians, to whom we are indebted. SoHO is a project of international collaboration between ESA and NASA."

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Download the 365-day GOLF frequencies

Download the 365-day GOLF frequency shifts

 

maj : 28-04-2015 (1130)

 

À l'écoute du Soleil
Qu'est ce que l'héliosismologie ? Tout comme la sismologie étudie les tremblements de Terre, l'héliosismologie étudie les tremblements du Soleil. Comme presque toutes les étoiles, la surface du Soleil est animée de mouvements d'oscillations. Ces pulsations naturelles et permanentes engendrent des ondes sonores ou de gravité qui se propagent dans l'étoile et permettent de l' étudier de la surface au coeur.  La source ... Lire la suite »
La sismologie : Qu'est-ce que c'est ? A quoi cela sert ?
P.A.P. Nghiem et R.A. García
POURQUOI LA SISMOLOGIE ? Le but est de sonder, d'étudier l'intérieur du Soleil (Héliosismologie) et des étoiles (Astérosismologie). A première vue, ce but peut sembler tout à fait rédhibitoire. Comment aller voir ce qui se passe à des millions de kilomètres à l'intérieur de ces gigantesque boules de feu où la température dépasse le million de degrés ? Justement, il ne faut pas chercher ... Lire la suite »
Le satellite SOHO
Fruit d'une collaboration entre la NASA et l'ESA, la sonde spatiale SOHO (Solar and Héliospheric Observatory) observe le soleil depuis 1996 à l'aide de 12 instruments complémentaires. Le Département d'Astrophysique, de Physique des Particules, de Physique Nucléaire et de l'Instrumentation associée (DAPN IA)  a participé à la construction de l'un d'entre eux, GOLF, pour étudier la sismologie solaire. Le satellite SOHO a une hauteur de 3.65 m, une ... Lire la suite »
 
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