Seismic halos around active regions: A magnetohydrodynamic theory

Research output: Contribution to journalArticle

Abstract

Comprehending the manner in which magnetic fields affect propagating waves is a first step toward constructing accurate helioseismic models of active region subsurface structure and dynamics. Here we present a numerical method for computing the linear interaction of waves with magnetic fields embedded in a solar-like stratified background. The ideal magnetohydrodynamic (MHD) equations are solved in a three-dimensional box that straddles the solar surface, extending from 35 Mm below the photosphere to 1.2 Mm into the atmosphere. One of the challenges in performing these simulations involves generating a magnetohydrostatic (MHS) state wherein the stratification assumes horizontal inhomogeneity in addition to the strong vertical stratification associated with the near-surface layers. Keeping in mind that the aim of this effort is to understand and characterize linear MHD interactions, we discuss a means of computing statically consistent background states. Power maps computed from simulations of waves interacting with thick flux tubes that have peak photospheric field strengths of 600 and 3000 G are presented. Strong modal power reduction in the "umbral" regions of the flux tube enveloped by a halo of increased wave power is seen in the simulations with the thick flux tubes. These enhancements are also seen in Doppler velocity power maps of active regions observed in the Sun, which leads us to propose that the halo has MHD underpinnings.

Original languageEnglish (US)
Pages (from-to)1457-1466
Number of pages10
JournalAstrophysical Journal
Volume680
Issue number2
DOIs
StatePublished - Jun 20 2008

Fingerprint

magnetohydrodynamics
halos
stratification
tubes
magnetic field
simulation
wave power
magnetohydrostatics
inhomogeneity
numerical method
surface layer
photosphere
magnetic fields
boxes
field strength
surface layers
sun
atmosphere
interactions
atmospheres

Keywords

  • Hydrodynamics
  • Sun: helioseismology
  • Sun: interior
  • Sun: oscillations
  • Waves

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Space and Planetary Science

Cite this

Seismic halos around active regions : A magnetohydrodynamic theory. / Hanasoge, Shravan.

In: Astrophysical Journal, Vol. 680, No. 2, 20.06.2008, p. 1457-1466.

Research output: Contribution to journalArticle

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