Hi all! In Ruth Durrer's book "The Cosmic Microwave Background" there is this picture (Fig. 5.2 page 193) about the E and B mode of the CMB polarization: http://imageshack.us/photo/my-images/11/s7o6.png/ http://imageshack.us/photo/my-images/11/s7o6.png/ They represent the E and B pattern around the photon direction. I probably don't fully understand what the E and B mode represent, because the tangential E mode looks like circular polarization to me, whereas circular polarization is not expected in the CMB and the E and B mode definitely describe linear polarization only. As for the B mode, I can't see how one can have the electric field oscillating in so many different directions. Summing up: do those lines represent oscillating electric field? If so, how can the E mode be tangential without circular polarization? How can there be multiple directions of oscillations for the B mode? Thanks in advance!