Talk at IAC solar seminar

At the IAC solar seminar I gave a talk on fast horizontal flows in solar granulation and their spectroscopic signatures. The pdf file with the presentation is here. Most of that work was done in collaboration with my Utrecht colleagues Catherine Fischer, Alexander Vogler and Christoph Keller and it has already been published in A&A (Vitas et al, 2011). Thanks those who attended the talk for a nice and lively discussion!

Figure shows profiles of Fe I 6301.5 A computed at the location of a large supersonic event that produced a shock front. They are computed at $\mu = 0.4$ (a position away from the center of the solar disk) and for 8 azimuthal directions. It's like we've been moving around the shock. The profiles are computed at high resolution, but degraded in both spatial and spectral domain to mimic the capabilities of the SP/SOT instrument at Hinode spacecraft. It is interesting to note how the asymmetry of the line changes with azimuth. When we see the flow is moving toward us (0 degrees), the blue wing of the profile is extended and distorted. When it is moving away from us (180 degrees), the red wing is affected. That behavior is due to the well-known Doppler effect. The figure tells us that the high velocity is not sufficient for the supersonic flows to be identified through line deformation. The velocity had to be roughly aligned with the line of sight of the observer.