Seismic sensitivity to sub-surface solar activity from 18 yr of GOLF/SoHO observations

Salabert, D.; García, R. A.; Turck‐Chièze, S.

doi:10.1051/0004-6361/201425236

Cited by 60 publications

(66 citation statements)

References 51 publications

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“…It can be shown that the changes between cycle 22 and 23 must occur above 2400km [26]. Salabert et al [27] showed a similar result can be obtained using GOLF data.…”

Section: Cycle-to-cycle Variationsmentioning

confidence: 53%

Seismological insights into solar and stellar magnetic activity cycles

Broomhall

2017

EPJ Web Conf.

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Abstract. The Sun's magnetic activity cycle varies primarily on a time scale of approximately 11yrs from minimum to maximum and back again. It is well-known that the properties of the Sun's acoustic oscillations are affected by the near-surface internal magnetic field: Frequencies, damping rates, and powers are all known to vary systematically with solar cycle. Careful observation of these variations, therefore, allows aspects of the Sun's internal magnetic field to be inferred. However, the Sun is just one star and, with CoROT and Kepler in particular, oscillations can now be observed for thousands of other stars. However, despite many stars showing signs of magnetic activity in their lightcurves, to date, activity cycle-like variations in the properties of asteroseimic oscillations are sparse. Nevertheless, studying the solar-stellar connection advances our understanding of solar and stellar magnetic fields. For example, placing our Sun's activity cycle in a stellar context suggests that the Sun may be unusual. Conversely, observations of quasi-periodic pulsations in stellar flares suggest the underlying physics of solar and stellar flares are the same.

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“…It can be shown that the changes between cycle 22 and 23 must occur above 2400km [26]. Salabert et al [27] showed a similar result can be obtained using GOLF data.…”

Section: Cycle-to-cycle Variationsmentioning

confidence: 53%

Seismological insights into solar and stellar magnetic activity cycles

Broomhall

2017

EPJ Web Conf.

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“…The frequencies of solar acoustic oscillations also show a well-documented solar-cycle variation (see Fossat et al 1987;Salabert et al 2015). The frequency shifts can be interpreted as arising from structural changes in the sub-surface layers, such as changes in temperature (Kuhn et al 1988) or in the size of the acoustic cavity (Dziembowski & Goode 2005).…”

Section: Introductionmentioning

confidence: 92%

“…Lefebvre et al (2009) showed that f -mode frequencies are mainly sensitive to the pressure scale height in the sub-surface layers. In a recent paper, Salabert et al (2015) analyzed eighteen A&A 595, A71 (2016) years of measurements of the GOLF experiment onboard SoHO to derive the temporal variability of the frequency shifts of the radial, dipolar, and quadrupolar modes for different frequency ranges sensitive to different layers in the solar sub-surface interior. They showed that the temporal evolution of the magnetic configuration imprints on these modes in a different way during cycle 23 and the weak on-going cycle 24.…”

Section: Introductionmentioning

confidence: 99%

Variation of the temperature gradient in the solar photosphere with magnetic activity

Faurobert

Raman

Ricort

2016

A&A

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Context. The contribution of quiet-Sun regions to the solar irradiance variability is currently unclear. Some solar-cycle variations of the quiet-Sun physical structure, such as the temperature gradient or the photospheric radius, might affect the irradiance. Aims. We intend to investigate possible variations of the photospheric temperature gradient with magnetic activity. Methods. We used high-resolution center-to-limb observations of the FeI 630.15 nm line profile in the quiet Sun performed onboard the Hinode satellite on 2007, December 19, and on 2013, December 7, that is, close to a minimum and a maximum of magnetic activity, respectively. We analyzed samples of 10 × 10 internetwork regions. The wings of the FeI 630.15 nm line were used in a non-standard way to recover images at roughly constant continuum optical depths above the continuum formation level. The image formation height is derived from measuring its perspective shift with respect to the continuum image, both observed away from disk center. The measurement relies on a cross-spectral method that is not limited by the spatial resolution of the SOT telescope and does not rely on any radiative transfer computation. The radiation temperature measured in the images is related to the photospheric temperature at their respective formation height. Results. The method allows us to investigate the temperature gradient in the low photosphere at altitudes of between 0 and 60 km above the 500 nm continuum formation height. In this layer the internetwork temperature gradient appears steeper in our 2013 sample than in the sample of 2007 in the northern hemisphere, whereas we detect no significant change in the southern hemisphere. We argue that this might be related to some strong hemispheric asymmetry of the magnetic activity at the solar maximum of cycle 24. Conclusions. Structural changes have been observed in numerical simulations of the magneto-convection at the surface of the Sun where the increase of the ambient sub-surface magnetic fields leads to some steepening of the temperature gradient in the internetwork. Hemispheric asymmetry of the activity has been reported for the last solar cycles with successive dominant north and south hemisphere during the activity maximum. Our results seem consistent with this global physical picture, but need to be confirmed by additional studies.

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“…The modes at higher frequencies show frequency shifts 30% smaller during Cycle 24, which is in agreement with the decrease observed in the surface activity between Cycles 23 and 24. The frequency tables associated with the work described in [57] are now available at the SPACEINN portal 7 . A total of 69 non-independent one-year frequency ta-bles of modes =0, 1, 2, and 3 are available.…”

Section: Comparison Of Solar Magnetic Activity Cycles 23-24mentioning

confidence: 99%

Global helioseismology (WP4.1): From the Sun to the stars & solar analogs

García

2017

EPJ Web Conf.

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Abstract. Sun-as-a star observations put our star as a reference for stellar observations. Here, I review the activities in which the SPACEINN global seismology team (Working Package WP4.1) has worked during the past 3 years. In particular, we will explain the new deliverables available on the SPACEINN seismic+ portal. Moreover, special attention will be given to surface dynamics (rotation and magnetic fields). After characterizing the rotation and the magnetic properties of around 300 solar-like stars and defining proper metrics for that, we use their seismic properties to characterize 18 solar analogues for which we study their surface magnetic and seismic properties. This allows us to put the Sun into context compared to its siblings.

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Seismic sensitivity to sub-surface solar activity from 18 yr of GOLF/SoHO observations

Cited by 60 publications

References 51 publications

Seismological insights into solar and stellar magnetic activity cycles

Seismological insights into solar and stellar magnetic activity cycles

Variation of the temperature gradient in the solar photosphere with magnetic activity

Global helioseismology (WP4.1): From the Sun to the stars & solar analogs

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