Bibcode
Braun, D.; Felipe, T.; Birch, A.; Crouch, A. D.
Referencia bibliográfica
American Astronomical Society, SPD meeting #47, id.#7.01
Advertised on:
5
2016
Número de citas
0
Número de citas referidas
0
Descripción
The interpretation of local helioseismic measurements of sunspots has
long been a challenge, since waves propagating through sunspots are
potentially affected by both mode conversion and changes in the thermal
structure of the spots. We carry out numerical simulations of wave
propagation through a variety of models which alternately isolate either
the thermal or magnetic structure of the sunspot or include both of
these. We find that helioseismic holography measurements made from the
resulting simulated wavefields show qualitative agreement with
observations of real sunspots. Using insight from ray theory, we find
that travel-time shifts in the thermal (non-magnetic) sunspot model are
primarily produced by changes in the wave path due to the Wilson
depression rather than variations in the wave speed. This shows that
inversions for the subsurface structure of sunspots must account for
local changes in the density. In some ranges of horizontal phase speed
and frequency there is agreement (within the noise level of the
measurements) between the travel times measured in the full magnetic
sunspot model and the thermal model. If this conclusion proves to be
robust for a wide range of models, it suggests a path towards inversions
for sunspot structure. This research has been funded by the Spanish
MINECO through grant AYA2014-55078-P, by the NASA Heliophysics Division
through NNX14AD42G and NNH12CF23C, and the NSF Solar Terrestrial program
through AGS-1127327.