STRATEGIES in SEISMIC INFERENCE of SUPERGRANULAR FLOWS on the SUN

Jishnu Bhattacharya, Shravan Hanasoge

    Research output: Contribution to journalArticle

    Abstract

    Observations of the solar surface reveal the presence of flows with length scales of around 35 Mm, commonly referred to as supergranules. Inferring the subsurface flow profile of supergranules from measurements of the surface and photospheric wavefield is an important challenge faced by helioseismology. Traditionally, the inverse problem has been approached by studying the linear response of seismic waves in a horizontally translationally invariant background to the presence of the supergranule; following an iterative approach that does not depend on horizontal translational invariance might perform better, since the misfit can be analyzed post iterations. In this work, we construct synthetic observations using a reference supergranule and invert for the flow profile using surface measurements of travel times of waves belonging to modal ridges f (surface gravity) and p 1 through p 7 (acoustic). We study the extent to which individual modes and their combinations contribute to infer the flow. We show that this method of nonlinear iterative inversion tends to underestimate the flow velocities, as well as inferring a shallower flow profile, with significant deviations from the reference supergranule near the surface. We carry out a similar analysis for a sound-speed perturbation and find that analogous near-surface deviations persist, although the iterations converge faster and more accurately. We conclude that a better approach to inversion would be to expand the supergranule profile in an appropriate basis, thereby reducing the number of parameters being inverted for and appropriately regularizing them.

    Original languageEnglish (US)
    Article number105
    JournalAstrophysical Journal
    Volume826
    Issue number2
    DOIs
    StatePublished - Aug 1 2016

    Fingerprint

    profiles
    iteration
    inversions
    deviation
    helioseismology
    acoustics
    seismic waves
    subsurface flow
    inverse problem
    seismic wave
    flow velocity
    travel time
    travel
    ridges
    invariance
    perturbation
    gravity
    gravitation
    inversion
    analysis

    Keywords

    • Sun: granulation
    • Sun: helioseismology
    • Sun: interior
    • Sun: oscillations

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    STRATEGIES in SEISMIC INFERENCE of SUPERGRANULAR FLOWS on the SUN. / Bhattacharya, Jishnu; Hanasoge, Shravan.

    In: Astrophysical Journal, Vol. 826, No. 2, 105, 01.08.2016.

    Research output: Contribution to journalArticle

    Bhattacharya, Jishnu ; Hanasoge, Shravan. / STRATEGIES in SEISMIC INFERENCE of SUPERGRANULAR FLOWS on the SUN. In: Astrophysical Journal. 2016 ; Vol. 826, No. 2.
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