Sound wave travel times in plage areas: The effect of abnormal granulation

K. Petrovay, R. Erdélyi, M. J. Thompson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We consider the effect that abnormal granulation observed in active regions should have on the propagation of acoustic waves. Any such effect is found to be limited to a shallow surface layer where sound waves propagate nearly vertically. The magnetically suppressed turbulence implies higher sound speeds, leading to shorter travel times. This time shift is independent of the travel distance, while it shows a characteristic dependence on the assumed plage field strength, plotted in Figure 2. As a consequence of the variation of the acoustic cutoff with height, the time shift is expected to be significantly higher for higher frequency waves within the observed regime of 3-5 mHz. The lower group velocity near the upper reflection point further leads to an increased envelope time shift, as compared to the phase shift. These characteristics of the time shifts are in accordance with observations. The calculated overall amplitude of the time shift is about ten seconds, comparable to, but still significantly less than suggested by measurements.

Original languageEnglish
Title of host publicationProceedings of SOHO-17
Subtitle of host publication10 Years of SOHO and Beyond
Edition617
Publication statusPublished - Jul 1 2006
EventSOHO-17: 10 Years of SOHO and Beyond - Sicily, Italy
Duration: May 7 2006May 12 2006

Publication series

NameEuropean Space Agency, (Special Publication) ESA SP
Number617
ISSN (Print)0379-6566

Other

OtherSOHO-17: 10 Years of SOHO and Beyond
CountryItaly
CitySicily
Period5/7/065/12/06

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Keywords

  • MHD
  • Magnetohydrodynamics
  • Sun

ASJC Scopus subject areas

  • Aerospace Engineering
  • Space and Planetary Science

Cite this

Petrovay, K., Erdélyi, R., & Thompson, M. J. (2006). Sound wave travel times in plage areas: The effect of abnormal granulation. In Proceedings of SOHO-17: 10 Years of SOHO and Beyond (617 ed.). (European Space Agency, (Special Publication) ESA SP; No. 617).