Meridional Circulation and Global Solar Oscillations

Roth, Markus; Stix, M.

doi:10.1007/s11207-008-9232-6

Cited by 43 publications

(46 citation statements)

References 32 publications

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“…frequencies of global p-modes are insensitive (to first order) to the meridional circulation, the flows have been detected with a variety of local seismic methods (e.g., Giles et al 1997;Braun & Fan 1998;González Hernández et al 1999;Haber et al 2002;Hughes & Thompson 2003;Zhao & Kosovichev 2004;Chou & Ladenkov 2005;Roth & Stix 2008). Many of these studies have focused their attention on the meridional circulation near the surface (e.g., within a few tens of Mm below the surface), and only a few attempts have been made to deduce the properties of the deeper components.…”

mentioning

confidence: 99%

Prospects for the Detection of the Deep Solar Meridional Circulation

Braun

Birch

2008

ApJ

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We perform helioseismic holography to assess the noise in p-mode travel-time shifts which would form the basis of inferences of large-scale flows throughout the solar convection zone. We also derive the expected travel times from a parameterized return (equatorward) flow component of the meridional circulation at the base of the convection zone from forward models under the assumptions of the ray and Born approximations. From estimates of the signal-to-noise ratio for measurements focused near the base of the convection zone, we conclude that the helioseismic detection of the deep meridional flow including the return component may not be possible using travel-time measurements spanning an interval less than a solar cycle. We speculate that this conclusion may be generally true for other helioseismic methods under the assumption that the underlying measurements are equivalently limited by solar realization noise.

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confidence: 99%

Prospects for the Detection of the Deep Solar Meridional Circulation

Braun

Birch

2008

ApJ

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“…According to theoretical forward calculations by Roth & Stix (2008) and Gough & Hindman (2010), the frequency shifts introduced by a meridional flow should be negligible. Given the results by Gough & Hindman (2010), the meridional flow should introduce a power redistribution among affected modes.…”

Section: Power Leaksmentioning

confidence: 99%

Verification of the helioseismic Fourier-Legendre analysis for meridional flow measurements

Roth

Doerr

Hartlep

2016

A&A

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Context. Measuring the Sun's internal meridional flow is one of the key issues of helioseismology. Using the Fourier-Legendre analysis is a technique for addressing this problem. Aims. We validate this technique with the help of artificial helioseismic data. Methods. The analysed data set was obtained by numerically simulating the effect of the meridional flow on the seismic wave field in the full volume of the Sun. In this way, a 51.2-h long time series was generated. The resulting surface velocity field is then analyzed in various settings: Two 360• × 90• halfspheres, two 120• × 60• patches on the front and farside of the Sun (North and South, respectively) and two 120• × 60• patches on the northern and southern frontside only. We compare two possible measurement setups: observations from Earth and from an additional spacecraft on the solar farside, and observations from Earth only, in which case the full information of the global solar oscillation wave field was available. Results. We find that, with decreasing observing area, the accessible depth range decreases: the 360• × 90• view allows us to probe the meridional flow almost to the bottom of the convection zone, while the 120• × 60• view means only the outer layers can be probed. Conclusions. These results confirm the validity of the Fourier-Legendre analysis technique for helioseismology of the meridional flow. Furthermore these flows are of special interest for missions like Solar Orbiter that promises to complement standard helioseismic measurements from the solar nearside with farside observations.

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“…Since unperturbed eigenfrequencies are not purely equidistant along the p-mode ridge, the meridional circulation can contribute slightly to the frequency splittings; this contribution has been addressed recently by Roth and Stix [9]. A weak point of the analysis reported in [9] is that when addressing the effects of the meridional flows, the differential rotation has been discarded.…”

Section: Mode Couplingmentioning

confidence: 99%

“…A weak point of the analysis reported in [9] is that when addressing the effects of the meridional flows, the differential rotation has been discarded. It is a distinctive property of the quasi-degenerate perturbation analysis that the result is not necessarily linear (additive) in the perturbation.…”

Section: Mode Couplingmentioning

confidence: 99%