HOP 0102

abstract of observational proposal

During this observation, the SOT observes a sunspot continuously for at least 12 hours with a constant cadence (about 1 min). Taking continuous ‘non-magnetic’ photospheric Dopplergrams of a sunspot is important for sunspot diagnostic by local helioseismology; since the Dopplergrams are not contaminated by magnetic fields, to investigate subsurface structure of the region where magnetic flux is strong, such as sunspots, it is useful. According to our previous works using the Dopplergrams, we need a continuous observation at least 12 hours to achieve sufficient S/N ratio. Coordination with MDI will be attempted.

request to SOT

-~1-min cadence. Constant cadence is highly required for our helioseismology analyses.
-Continuous observation for 12 hours at least.
-NFI: Fe I 557.6nm Dopplergram
-BFI: Ca II H
-If NFI takes 1024x512 Dopplergrams with 4x4 summing (Q65) and BFI takes 2048x1024 images with 2x2 summing (Q50) by using program ID:0x1f5( Mar 15 and Oct 11, 2008), estimated data volume is ~211Mbits per hour. We want to continue the observation at least 12 hours as long as telemetry permits.
-Another choice is: only NFI takes 2048x1024 Dopplergrams with 2x2 summing for 12 hours. If the compression factor is set at Q75, estimated data volume is about 450Mbits per hour in this case.

remarks

Target of interest: Sunspots. (TOO)

Abstract of Lindsay

Discriminating Helioseismic Signatures of Fast- and Slow-Mode Coupling in Inclined-Magnetic Regions

A critical element of active-region helioseismology is understanding the effects of the near-surface layers of magnetic regions on seismic signatures in active-region photospheres. Major theoretical developments have come from recognition of the connection between wave absorption by active regions and a strong inequality between in-going and out-going acoustic travel times therefrom. A major contributor to the travel-time inequality is now thought to be strong coupling between fast and slow magnetoacoustic modes in inclined-field regions, such as sunspot penumbrae. A crucial diagnostic development has been the recognition by Schunker et al. of the vantage dependence of helioseismic signatures in sunspot penumbrae, particularly a behavior we sometimes call ``phase parallax.'' A clear understanding of mode coupling that accommodates phase parallax is imperative for detailed modeling of the subphotospheres of magnetic regions based on helioseismic signatures. However, an additional likely contributor to phase parallax in Doppler maps made in magnetically sensitive lines is radiative-transfer (RT) effects due to Zeeman splitting recognized by Rajaguru et al. These RT effects are understood to be null in magnetically insensitive lines. An extension of the experiments of Schunker et al. with seismic observations of sunspot penumbrae in a magnetically insensitive line is needed to discriminate travel-time perturbations due to mode coupling from the RT effects. This can be accomplished with simultaneous, co-aligned helioseismic observations of active regions from {\it SDO}/HMI and Hinode.