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Title:
Simulations of Acoustic Excitation
Authors:
Lindsey, C.; Birch, A. C.; Donea, A.-C.
Publication:
Solar MHD Theory and Observations: A High Spatial Resolution Perspective ASP Conference Series, Vol. 354, Proceedings of the Conference Held 18-22 July, 2005, at the National Solar Observatory, Sacramento Peak, Sunspot, New Mexico, USA. Edited by J. Leibacher, R. F. Stein, and H. Uitenbroek. San Francisco: Astronomical Society of the Pacific, 2006., p.174
Publication Date:
12/2006
Origin:
ASP
Bibliographic Code:
2006ASPC..354..174L

Abstract

Acoustic emission from solar granulation is thought to be relatively localized and episodic, emanating largely as relatively discrete wavepackets emitted from convective plumes falling into the solar interior from near-surface layers at which granular convection takes place. We devise preliminary simulated sound computations to characterize the range of acoustic signatures that can be expected from random localized emission for a range of surface densities and mean episodic frequencies. In the simple models studied here wave excitation is represented by dipole emitters at a depth of one~Mm randomly distributed in time and location over the surface of a standard solar model. We apply holographic regressions to the resulting surface acoustic fields and compile acoustic power statistics on the resulting helioseismic signatures. Acoustic power statistics of random, stationary Gaussian noise are characterized by an exponential distribution. The relatively localized and episodic nature of acoustic emission expected from downfalling plumes should be distinguishable from Gaussian noise by a characteristic deviation from the exponential distribution. If the episodes are relatively dense and frequent compared to the temporal and spatial discrimination of the helioseismic diagnostics, the deviation from Gaussian statistics becomes small. Simulations of acoustic emission, then, allow us to assess the potential of local helioseismic diagnostics for recognizing episodic excitation of acoustic waves.

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