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High-frequency acoustic waves are not sufficient to heat the solar chromosphere

Nature volume 435, pages 919–921 (2005)Cite this article

Abstract

One of the main unanswered questions in solar physics is why the Sun's outer atmosphere is hotter than its surface. Theory predicts abundant production of high-frequency (10–50 mHz) acoustic waves in subsurface layers of the Sun1, and such waves are believed by many to constitute the dominant heating mechanism of the chromosphere (the lower part of the outer solar atmosphere) in non-magnetic regions2,3,4. Such high-frequency waves are difficult to detect because of high-frequency disturbances in Earth's atmosphere (seeing) and other factors. Here we report the detection of high-frequency waves, and we use numerical simulations to show that the acoustic energy flux of these waves is too low, by a factor of at least ten, to balance the radiative losses in the solar chromosphere. Acoustic waves therefore cannot constitute the dominant heating mechanism of the solar chromosphere.

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Figure 1: Power of observed 1,600 Å TRACE relative intensity fluctuations.
Figure 2: Power of the acoustic energy fluxes in the simulations.
Figure 3: Simulated and observed 1,600 Å TRACE intensity fluctuations.
Figure 4: Simulated and derived acoustic energy fluxes at a height of 400 km.

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Acknowledgements

This work was supported by the Research Council of Norway and by a grant of computing time from the Program for Supercomputing. We thank T. Tarbell, B. De Pontieu and the TRACE instrument team for their support.

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  1. Institute of Theoretical Astrophysics, University of Oslo, PB 1029, 0315, Blindern, Oslo, Norway

    Astrid Fossum & Mats Carlsson

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  1. Astrid Fossum
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Correspondence to Astrid Fossum.

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Fossum, A., Carlsson, M. High-frequency acoustic waves are not sufficient to heat the solar chromosphere. Nature 435, 919–921 (2005). https://doi.org/10.1038/nature03695

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