Subwavelength Resolution Imaging of the Solar Deep Interior
Abstract
We derive expectations for signatures in the measured travel times of waves that interact with thermal anomalies and jets. A series of numerical experiments that involve the dynamic linear evolution of an acoustic wave field in a solarlike stratified spherical shell in the presence of fully three-dimensional time-stationary perturbations are performed. The imprints of these interactions are observed as shifts in wave travel times, which are extracted from these data through methods of time-distance helioseismology (Duvall et al.). In situations where at least one of the spatial dimensions of the scatterer was smaller than a wavelength, oscillatory time shift signals were recovered from the analyses, pointing directly to a means of resolving subwavelength features. As evidence for this claim, we present analyses of simulations with spatially localized jets and sound-speed perturbations. We analyze one year's worth solar observations to estimate the noise level associated with the time differences. Based on theoretical estimates, Fresnel zone time shifts associated with the (possible) sharp rotation gradient at the base of the convection zone are on the order of 0.01-0.1 s, well below the noise level that could be reached with the currently available amount of data (~0.15 - 0.2 s with 10 yr of data).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2009
- DOI:
- 10.1088/0004-637X/693/2/1678
- arXiv:
- arXiv:0812.0119
- Bibcode:
- 2009ApJ...693.1678H
- Keywords:
-
- Sun: helioseismology;
- Sun: interior;
- Sun: oscillations;
- waves;
- hydrodynamics;
- Astrophysics
- E-Print:
- Accepted, ApJ