We evaluate the possible use of three-dimensional, time-dependent simulations for the generation of artificial data to be used to develop and calibrate helioseismology inversion methods. We analyze flow fields from the simulations of Stein & Nordlund for the upper convection layer by splitting the velocity field into a rotational component and a potential component. The aim is to separate the turbulence from the acoustics. In general, turbulence is defined to be vortical while acoustics is potential. We find that the two fields are weakly coupled. The vorticity temporal normalized power shows a weak resonance at the fundamental frequency. We find that most of the (kinetic) energy is in the vortical component indicating that the potential component can be treated as a small perturbation relative to the vortical field. However, for a given mode we find that the temporal power is mostly in the potential component. These results indicate that we can treat the potential component as a small perturbation. They also show why helioseismology works even in a highly turbulent environment. To generate artificial helioseismic data, we plan to propagate acoustic waves through frozen fields from simulations of the solar convection zone. We show preliminary results where we follow an acoustic wave as it interacts with a frozen speed of sound perturbation in full spherical geometry. A series of near-circular scattered waves diverge from the perturbation, extracting energy from the original wave.
|Original language||English (US)|
|Number of pages||8|
|Journal||European Space Agency, (Special Publication) ESA SP|
|State||Published - Dec 1 2004|
All Science Journal Classification (ASJC) codes
- Aerospace Engineering