The Acoustic Showerglass. II. Imaging Active Region Subphotospheres

Details The Acoustic Showerglass. II. Imaging Active Region Subphotospheres The Acoustic Showerglass. II. Imaging Active Region Subphotospheres

Feb 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005apj...620.1118l&link_type=abstract

The Astrophysical Journal, Volume 620, Issue 2, pp. 1118-1131.

Astronomy and Astrophysics

Astronomy

31

Sun: Activity, Sun: Helioseismology, Sun: Magnetic Fields, Sun: Oscillations, Sun: Sunspots

Scientific paper

Seismic diagnostics of the shallow subphotospheres of strong active regions are substantially impacted by large amplitude and phase perturbations introduced by overlying surface magnetic fields. These function as an ``acoustic showerglass'' that impairs the coherence of acoustic waves impinging onto the solar surface from below, degrading images of subsurface anomalies derived by phase-coherent seismic reconstruction. In an independent study we have developed a rough proxy to characterize showerglass phase errors based on maps of the square magnitude of the vector magnetic field at the surface. In this study we apply the proxy to correct helioseismic observations of active region photospheres from the Michelson Doppler Imager aboard the Solar and Heliospheric Observatory. We apply phase-correlation seismic holography to the corrected observations to image the underlying 5-10 Mm subphotosphere. The corrected phase maps show no consistent evidence for sound-speed anomalies more than 5 Mm beneath a moderately large, isolated sunspot. Forward-modeling computations applied to simple models suggest sound-speed anomalies limited to approximately +/-250 m s-1 for depths from 5 to 10 Mm, averaged over the horizontal extent of the sunspot. For complex active regions, uncertainties are considerably greater. However, results of this study suggest that more careful modeling of the acoustic showerglass will lead to substantially improved seismic diagnostics of active region subphotospheres. Detailed hydromechanical computations of acoustics models of active region photospheres and subphotospheres are needed to facilitate the interpretation of showerglass-corrected holographic signatures.

Affiliated with

Also associated with

No associations

Rating

The Acoustic Showerglass. II. Imaging Active Region Subphotospheres does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Acoustic Showerglass. II. Imaging Active Region Subphotospheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Acoustic Showerglass. II. Imaging Active Region Subphotospheres will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1749240