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We present evidence for the dependence of helioseismic Doppler signatures in active regions on the line-ofsight angle in inclined magnetic fields. Using data from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory, we performed phase-sensitive holography in the penumbrae of sunspots over the course of several days as the spots traversed the solar disk. Control correlations, which comprise a correlation of the surface wave amplitude with the incoming acoustic wave amplitude from a surrounding region, were mapped. There is a direct dependence of control-correlation phase signatures on the line-of-sight angle in the plane defined by the vertical and magnetic field vectors. The phase shift of waves observed along directions close to the orientation of the magnetic field is smaller than the phase shift observed when the line of sight is at a significant angle with respect to the field orientation. These findings have important implications for local helioseismology. The variation in phase shift (or the equivalent acoustic travel-time perturbations) with line-ofsight direction suggests that a substantial portion of the phase shift occurs in the photospheric magnetic field. Observations of the vector components of the field may be used to develop a proxy to correct these phase perturbations (known as the acoustic showerglass) that introduce uncertainties in the signatures of acoustic perturbations below the surface.

We have used helioseismic holography to render seismic images of the solar flare of 1996 July 9, whose helioseismic signature was recently reported by Kosovichev & Zharkova. We computed time series of "egression power maps" in 2 mHz bands centered at 3.5 and 6 mHz. These images suggest an oblong acoustic source associated with the flare some 18 Mm in the north-south direction and approximately 15 Mm in the east-west direction. The considerable preponderance of the flare acoustic power emanates in the 3.5 mHz band. However, because the ambient noise in the 6 mHz band is much lower and the diffraction limit for 6 mHz waves is much finer, the flare is rendered far more clearly in the 6 mHz band. The 6 mHz flare signature lags the 3.5 mHz by approximately 4 minutes.

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