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Accurate Mapping of the Torsional Oscillations: a Trade-Off Study between Time Resolution and Mode Characterization Precision

Auteur

Korzennik Sylvain

Institution

Harvard-Smithsonian Center for Astrophysics

Theme

Convection, dynamo and flows
Auteur(s) supplémentaire(s)Eff-Darwich, Antonio
Institution(s) supplémentaire(s)Instituto de Astrofisica de Canarias, Tenerife, Spain

Abstract

One salient result of global helioseismology is the mapping of the so-called
torsional oscillations below the solar surface. These subsurface flows are
inferred by inverting rotational frequency splitting sets of global
modes. These flows extent down to a depth of at least 0.8 R, and are likely
associated with the activity cycle of our star. To better understand the
mechanisms that drive the solar cycle we need to accurately map these flows,
and characterize precisely their penetration depth and their temporal behavior.

We present a detailed study of the spatio-temporal variation of the solar
rotation rate associated with the torsional oscillation based on
state-of-the-art mode fitting of time series of various lengths of MDI
observations. The times-series analyzed cover a full solar cycle, or 4608 days.
That epoch was fitted using various length overlapping segments. Such approach
allows us to better estimate how much significant information can be extracted
from the different time spans and hence trade-off time resolution for
precision in the inverted profiles resulting from the different mode sets.
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