First measurement of the polarization of the flash spectrum during a total solar eclipse.

Total solar eclipses offer the unique opportunity for a clean observation of the light emitted by different chromospheric layers without being disturbed by photospheric stray light, since the moon is operating as a sharp knife edge. During the 29th March 2006 total solar eclipse we thus performed a pioneering measurement of the polarization of the flash spectrum from UV to the near IR with a spectral resolution of order 0.6 nm. The measurement has been obtained with a dedicated instrument composed of an 8-inch Dall-Kirkham type telescope and a slitless spectropolarimeter. The complete flash phase at the second contact was observed with a cadence of 25 frames per second corresponding to a height resolution of about 20 km in the solar atmosphere. We could nicely register the dramatic transition from an absorption-line spectrum to an emission spectrum dominated by the strong chromospheric resonance lines. At the third contact we recorded the opposite transition with a variable frame ratereaching up to 75 frames per second. The results of our spectacular and interesting observations will be presented.