Fig. 5(a) of T.B. Mitchell, J.J. Bollinger, X.-P. Huang, and W.M. Itano, "Doppler imaging of plasma modes in a Penning trap,"
Optics Express 2, 314-322 (1998). Movie of sideview image data obtained on a plasma while driving at a frequency near a crossing of a (2,0) mode and a (8,0) mode. See text for details.