Helioseismic and Magnetic Imager Multi-height Dopplergrams
  We study Doppler velocity measurements at multiple heights in the solar atmosphere using a set of six filtergrams obtained by the Helioseismic magnetic Imager on board the Solar Dynamics Observatory. There are clear and significant phase differences between core and wing Dopplergrams in the frequency range above the photospheric acoustic cutoff frequency, which indicates that these are really "multi-height" datasets. 
Kaori Nagashima (1), Laurent Gizon (1,2), Aaron Birch (1), Bj\"orn   L\"optien (2), Sebastien Couvidat (3), Bernhard Fleck (...
astro-ph.SR