Table 1
Spatially averaged travel-time shift introduced by the perturbation to the sunspot model, ⟨ ΔQSτ(RS + pert) ⟩ − ⟨ ΔQSτ(RS) ⟩.
| Sunspot perturbation | Travel-time shift (s) | ||
| f | p1 | p2 | |
|
|
|||
| Wilson depression: | |||
| 50 km deeper | +0.4 | −2.2 | −3.8 |
| 50 km shallower | −0.3 | +1.9 | +3.2 |
|
|
|||
| Alternative magnetic field | −2.4 | −2.8 | -3.3 |
|
|
|||
| Sound-speed perturbations: | |||
| A = 0.1, h = −2 Mm | 0.0 | −0.4 | −0.8 |
| A = 0.1, h = −3 Mm | 0.0 | −0.8 | −0.6 |
| A = 0.1, h = −4 Mm | 0.0 | −0.8 | −0.2 |
| A = 0.5, h = −1.5 Mm | ... | −1.2 | ... |
Notes. Negative (positive) indicates that the waves travel faster (slower) through the perturbed model than the reference sunspot model. The systematic error introduced by the measurement procedure is ≈0.1 s. The noise level for seven days of SOHO/MDI observations for the f, p1, and p2 mode is 3.7 s, 3.5 s, and 1.6 s respectively. The travel-time shifts in bold lie above the noise level.
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