Photospheric Origin of Three-minute Oscillations in a Sunspot

Jongchul Chae, Jeongwoo Lee, Kyuhyoun Cho, Donguk Song, Kyungsuk Cho, Vasyl Yurchyshyn

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The origin of the three-minute oscillations of intensity and velocity observed in the chromosphere of sunspot umbrae is still unclear. We investigated the spatio-spectral properties of the 3 minute oscillations of velocity in the photosphere of a sunspot umbra as well as those in the low chromosphere using the spectral data of the Ni i λ5436, Fe i λ5435, and Na i D2 λ5890 lines taken by the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope at the Big Bear Solar Observatory. As a result, we found a local enhancement of the 3 minute oscillation power in the vicinities of a light bridge (LB) and numerous umbral dots (UDs) in the photosphere. These 3 minute oscillations occurred independently of the 5 minute oscillations. Through wavelet analysis, we determined the amplitudes and phases of the 3 minute oscillations at the formation heights of the spectral lines, and they were found to be consistent with the upwardly propagating slow magnetoacoustic waves in the photosphere with energy flux large enough to explain the chromospheric oscillations. Our results suggest that the 3 minute chromospheric oscillations in this sunspot may have been generated by magnetoconvection occurring in the LB and UDs.

Original languageEnglish (US)
Article number18
JournalAstrophysical Journal
Volume836
Issue number1
DOIs
StatePublished - Feb 10 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Sun: atmosphere
  • Sun: chromosphere
  • Sun: magnetic fields
  • Sun: oscillations
  • hydrodynamics
  • waves

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