  We calculate the iron line profiles from accretion discs with spiral velocity
structures around Schwarzschild black holes. We find that quasi-periodic bumps
appear in the the profiles, thereby providing a test for spiral wave patterns.
This study is motivated by recent work showing that spiral density waves can
result from MHD instabilities even in non-self-gravitating discs, and by
improved spectral resolution of forthcoming X-ray missions.
