Combined helioseismic inversions for 3D vector flows and sound-speed perturbations. (arXiv:1901.01293v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Korda_D/0/1/0/all/0/1">David Korda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Svanda_M/0/1/0/all/0/1">Michal Švanda</a>
Time-distance helioseismology is the method of the study of the propagation
of waves through the solar interior via the travel times of those waves. The
travel times of wave packets contain information about the conditions in the
interior integrated along the propagation path of the wave. We introduce an
improved methodology of the time-distance helioseismology which allows us to
invert for a full 3D vector of flows and the sound-speed perturbations at once.
Using this methodology one can also derive the mean value of the vertical
component of flows and the cross-talk between the flows and the sound-speed
perturbations. We used the SOLA method with a minimisation of the cross-talk as
a tool for inverse modelling. In the forward model, we use Born approximation
travel-time sensitivity kernels with the Model S as a background. The
methodology was validated using forward-modelled travel times with both mean
and difference point-to-annulus averaging geometries applied to a snapshot of
fully self-consistent simulation of the convection. We tested the methodology
on synthetic data. We demonstrate that we are able to recover flows and
sound-speed perturbations in the near-surface layers. We have taken the
advantage of the sensitivity of our methodology to entire vertical velocity,
and not only to its variations as in other available methodologies. The
cross-talk from both the vertical flow component and the sound-speed
perturbation has only a negligible effect for inversions for the horizontal
flow components. The inversions for the vertical component of the vector flows
or for the sound-speed perturbations are affected by the cross-talk from the
horizontal components, which needs to be minimised in order to provide valid
results. It seems that there is a nearly constant cross-talk between the
vertical component of the vector flows and the sound-speed perturbations.
Time-distance helioseismology is the method of the study of the propagation
of waves through the solar interior via the travel times of those waves. The
travel times of wave packets contain information about the conditions in the
interior integrated along the propagation path of the wave. We introduce an
improved methodology of the time-distance helioseismology which allows us to
invert for a full 3D vector of flows and the sound-speed perturbations at once.
Using this methodology one can also derive the mean value of the vertical
component of flows and the cross-talk between the flows and the sound-speed
perturbations. We used the SOLA method with a minimisation of the cross-talk as
a tool for inverse modelling. In the forward model, we use Born approximation
travel-time sensitivity kernels with the Model S as a background. The
methodology was validated using forward-modelled travel times with both mean
and difference point-to-annulus averaging geometries applied to a snapshot of
fully self-consistent simulation of the convection. We tested the methodology
on synthetic data. We demonstrate that we are able to recover flows and
sound-speed perturbations in the near-surface layers. We have taken the
advantage of the sensitivity of our methodology to entire vertical velocity,
and not only to its variations as in other available methodologies. The
cross-talk from both the vertical flow component and the sound-speed
perturbation has only a negligible effect for inversions for the horizontal
flow components. The inversions for the vertical component of the vector flows
or for the sound-speed perturbations are affected by the cross-talk from the
horizontal components, which needs to be minimised in order to provide valid
results. It seems that there is a nearly constant cross-talk between the
vertical component of the vector flows and the sound-speed perturbations.
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