Solar Physics

, Volume 82, Issue 1–2, pp 411–425 | Cite as

Variability in the power spectrum of solar five-minute oscillations

  • Frank Hill
  • Juri Toomre
  • Laurence J. November
Invited Review

Abstract

Two-dimensional power spectra of solar five-minute oscillations display prominent ridge structures in (k, ω) space, where k is the horizontal wavenumber and ω is the temporal frequency. The positions of these ridges in k and ω can be used to probe temperature and velocity structures in the subphotosphere. We have been carrying out a continuing program of observations of five-minute oscillations with the diode array instrument on the vacuum tower telescope at Sacramento Peak Observatory (SPO). We have sought to establish whether power spectra taken on separate days show shifts in ridge locations; these may arise from different velocity and temperature patterns having been brought into our sampling region by solar rotation. Power spectra have been obtained for six days of observations of Doppler velocities using the Mgiλ5173 and Feiλ5434 spectral lines. Each data set covers 8 to 11 hr in time and samples a region 256″ × 1024″ in spatial extent, with a spatial resolution of 2″ and temporal sampling of 65 s. We have detected shifts in ridge locations between certain data sets which are statistically significant. The character of these displacements when analyzed in terms of eastward and westward propagating waves implies that changes have occurred in both temperature and horizontal velocity fields underlying our observing window. We estimate the magnitude of the velocity changes to be on the order of 100 m s-1; we may be detecting the effects of large-scale convection akin to giant cells.

Keywords

Power Spectrum Velocity Structure Horizontal Velocity Temporal Frequency Doppler Velocity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© D. Reidel Publishing Co 1983

Authors and Affiliations

  • Frank Hill
    • 1
  • Juri Toomre
    • 1
  • Laurence J. November
    • 2
  1. 1.Department of Astrophysical, Planetary and Atmospheric Sciences, and Joint Institute for Laboratory AstrophysicsUniversity of ColoradoBoulderU.S.A.
  2. 2.Air Force Geophysics Laboratory and AURA, Sacramento Peak ObservatorySunspotU.S.A.

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