Local Fractional Frequency Shifts Used as Tracers of Magnetic Activity

  • Bradley Hindman
  • Deborah Haber
  • Juri Toomre
  • Rick Bogart

Abstract

Using data from SOI-MDI (Haber et al, 2000), we compute the local frequencies of high-degree p modes and f modes. The frequencies are obtained through ring-diagram mode fitting. The Dense-Pack data set consists of a mosaic of 189 overlapping tiles, each tracked separately at the surface rotation rate over 1664-min time intervals during the Dynamics Programs. Each tile is 16° square and the tile centers are separated by 7.5° in latitude and longitude. For each sampling day and for each tile, we have computed the frequency shift measured relative to the temporal and spatial average of the entire set of frequencies. The motion of active regions as they rotate across the solar disk is vividly traced by these measurements. Active regions appear as locations of large positive frequency shifts. If the shifts are averaged over the solar disk and are scaled down to the appropriate wave number regime, the magnitude and frequency dependence of the shifts are consistent with the measured changes in global oscillation frequencies that occur over the solar cycle. As with the frequency shifts of low-degree global oscillations, the frequency dependence of the shifts indicates that the physical phenomena inducing the shifts is confined to the surface layers of the Sun.

Keywords

Dynamics Program Frequency Shift Solar Cycle Mode Order Solar Disk 
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

© Springer Science+Business Media Dordrecht 2000

Authors and Affiliations

  • Bradley Hindman
    • 1
  • Deborah Haber
    • 1
  • Juri Toomre
    • 1
  • Rick Bogart
    • 2
  1. 1.JILA, University of ColoradoBoulderUSA
  2. 2.CSSA, Stanford UniversityStanfordUSA

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