Five-minute oscillation power within magnetic elements in the solar atmosphere
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AbstractIt has long been known that magnetic plage and sunspots are regions in which the power of acoustic waves is reduced within the photospheric layers. Recent observations now suggest that this suppression of power extends into the low chromosphere and is also present in small magnetic elements far from active regions. In this paper we investigate the observed power suppression in plage and magnetic elements, by modeling each as a collection of vertically aligned magnetic fibrils and presuming that the velocity within each fibril is the response to buffeting by incident p modes in the surrounding field-free atmosphere. We restrict our attention to modeling observations made near the solar disk center, where the line-of-sight velocity is nearly vertical and hence, only the longitudinal component of the motion within the fibril contributes. Therefore, we only consider the excitation of axisymmetric sausage waves and ignore kink oscillations as their motions are primarily horizontal. We compare the vertical motion within the fibril with the vertical motion of the incident p mode by constructing the ratio of their powers. In agreement with observational measurements we find that the total power is suppressed within strong magnetic elements for frequencies below the acoustic cut-off frequency. However, further physical effects need to be examined for understanding the observed power ratios for stronger magnetic field strengths and higher frequencies. We also find that the magnitude of the power deficit increases with the height above the photosphere at which the measurement is made. Furthermore, we argue that the area of the solar disk over which the power suppression extends increases as a function of height.
CitationFive-minute oscillation power within magnetic elements in the solar atmosphere, The Astrophysical Journal, 796 (2):72
JournalThe Astrophysical Journal
DescriptionThis is an accepted manuscript of an article published by American Astronomical Society in Astrophysical Journal on 06/11/2014, available online: https://doi.org/10.1088/0004-637X/796/2/72 The accepted version of the publication may differ from the final published version.
SponsorsSTFC (UK) and NASA grants NNX09AB04G, NNX14AC05G, and NNX14AG05G
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