Linear sensitivity of helioseismic travel times to local flows

A. C. Birch, L. Gizon

Research output: Contribution to journalArticlepeer-review

Abstract

Time-distance helioseismology is a technique for measuring the time for waves to travel from one point on the solar surface to another. These wave travel times are affected by advection by subsurface flows. Inferences of plasma flows based on observed travel times depend critically on the ability to accurately model the effects of subsurface flows on time-distance measurements. We present a Born-approximation based computation of the sensitivity of time-distance travel times to weak, steady, inhomogeneous subsurface flows. Three sensitivity functions are obtained, one for each component of the 3D vector flow. We show that the depth sensitivity of travel times to horizontally uniform flows is given approximately by the kinetic energy density of the oscillation modes which contribute to the travel times. For flows with strong depth dependence, the Born approximation can give substantially different results than the ray approximation.

Original languageEnglish (US)
Pages (from-to)228-233
Number of pages6
JournalAstronomische Nachrichten
Volume328
Issue number3-4
DOIs
StatePublished - Mar 2007

Keywords

  • Sun: helioseismology
  • Sun: interior

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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