Detection of zonal shear flows beneath the Sun's surface from f-mode frequency splitting

A. G. Kosovichev; J. Schou

doi:10.1086/310708

Detection of zonal shear flows beneath the Sun's surface from f-mode frequency splitting

A. G. Kosovichev, J. Schou

Research output: Contribution to journal › Article › peer-review

81 Scopus citations

Abstract

We report on the first successful measure of the zonal variations of the Sun's differential rotation (so-called torsional oscillations) by helioseismology. Using new helioseismic data from the Michelson Doppler Imager on board SOHO, we have detected zonal flow bands with velocity variation of 5 m s^-1 at a depth of 2-9 Mm beneath the surface. The subsurface flow is inferred from rotational splitting of frequencies of the fundamental mode of solar oscillations in the range of angular degree l from 120 to 250, using a 144 day uninterrupted time series of the Sun's Doppler velocities. The structure of the subsurface shear flow resembles the pattern of the torsional oscillations observed on the surface. Comparing with previous surface measurements, we found evidence for migration of the flow bands towards the equator.

Original language	English (US)
Pages (from-to)	L207-L210
Journal	Astrophysical Journal
Volume	482
Issue number	2 PART II
DOIs	https://doi.org/10.1086/310708
State	Published - 1997
Externally published	Yes

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

Keywords

Convection
Methods: data analysis
Sun: activity
Sun: interior
Sun: oscillations
Sun: rotation

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10.1086/310708

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title = "Detection of zonal shear flows beneath the Sun's surface from f-mode frequency splitting",

abstract = "We report on the first successful measure of the zonal variations of the Sun's differential rotation (so-called torsional oscillations) by helioseismology. Using new helioseismic data from the Michelson Doppler Imager on board SOHO, we have detected zonal flow bands with velocity variation of 5 m s-1 at a depth of 2-9 Mm beneath the surface. The subsurface flow is inferred from rotational splitting of frequencies of the fundamental mode of solar oscillations in the range of angular degree l from 120 to 250, using a 144 day uninterrupted time series of the Sun's Doppler velocities. The structure of the subsurface shear flow resembles the pattern of the torsional oscillations observed on the surface. Comparing with previous surface measurements, we found evidence for migration of the flow bands towards the equator.",

keywords = "Convection, Methods: data analysis, Sun: activity, Sun: interior, Sun: oscillations, Sun: rotation",

author = "Kosovichev, {A. G.} and J. Schou",

note = "Funding Information: We thank Peter Gilman for commenting, as referee, on the original submitted version of this paper. We thank also J{\o}rgen Christensen-Dalsgaard, Tom Duvall, Douglas Gough, Phil Scherrer, and Juri Toomre for useful comments and discussions. The authors acknowledge many years of effort by the engineering and support staff of the MDI development team at the Lockheed Palo Alto Research Laboratory (now Lock-heed-Martin Advanced Technology Center) and the SOI development team at Stanford University. SOHO is a project of international cooperation between ESA and NASA. This research is supported by the SOI-MDI NASA contract NAG5-3077 at Stanford University.",

year = "1997",

doi = "10.1086/310708",

language = "English (US)",

volume = "482",

pages = "L207--L210",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2 PART II",

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TY - JOUR

T1 - Detection of zonal shear flows beneath the Sun's surface from f-mode frequency splitting

AU - Kosovichev, A. G.

AU - Schou, J.

N1 - Funding Information: We thank Peter Gilman for commenting, as referee, on the original submitted version of this paper. We thank also Jørgen Christensen-Dalsgaard, Tom Duvall, Douglas Gough, Phil Scherrer, and Juri Toomre for useful comments and discussions. The authors acknowledge many years of effort by the engineering and support staff of the MDI development team at the Lockheed Palo Alto Research Laboratory (now Lock-heed-Martin Advanced Technology Center) and the SOI development team at Stanford University. SOHO is a project of international cooperation between ESA and NASA. This research is supported by the SOI-MDI NASA contract NAG5-3077 at Stanford University.

PY - 1997

Y1 - 1997

N2 - We report on the first successful measure of the zonal variations of the Sun's differential rotation (so-called torsional oscillations) by helioseismology. Using new helioseismic data from the Michelson Doppler Imager on board SOHO, we have detected zonal flow bands with velocity variation of 5 m s-1 at a depth of 2-9 Mm beneath the surface. The subsurface flow is inferred from rotational splitting of frequencies of the fundamental mode of solar oscillations in the range of angular degree l from 120 to 250, using a 144 day uninterrupted time series of the Sun's Doppler velocities. The structure of the subsurface shear flow resembles the pattern of the torsional oscillations observed on the surface. Comparing with previous surface measurements, we found evidence for migration of the flow bands towards the equator.

AB - We report on the first successful measure of the zonal variations of the Sun's differential rotation (so-called torsional oscillations) by helioseismology. Using new helioseismic data from the Michelson Doppler Imager on board SOHO, we have detected zonal flow bands with velocity variation of 5 m s-1 at a depth of 2-9 Mm beneath the surface. The subsurface flow is inferred from rotational splitting of frequencies of the fundamental mode of solar oscillations in the range of angular degree l from 120 to 250, using a 144 day uninterrupted time series of the Sun's Doppler velocities. The structure of the subsurface shear flow resembles the pattern of the torsional oscillations observed on the surface. Comparing with previous surface measurements, we found evidence for migration of the flow bands towards the equator.

KW - Convection

KW - Methods: data analysis

KW - Sun: activity

KW - Sun: interior

KW - Sun: oscillations

KW - Sun: rotation

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JF - Astrophysical Journal

IS - 2 PART II

ER -

Detection of zonal shear flows beneath the Sun's surface from f-mode frequency splitting

Abstract

All Science Journal Classification (ASJC) codes

Keywords

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