  We present observations and results of radiance and irradiance studies
completed by SoHO-SUMER during the past solar cycle. We find that the cycle
variation in Ly-alpha irradiance as observed by e.g. UARS-SOLSTICE can not be
explained by quiet sun radiance data, and conclude that the explanation must be
related to differences in the Ly-alpha radiance of various solar features and
changes in their fractional distribution over the solar cycle. Consequently, we
studied the emission of the hydrogen Ly-alpha line in various solar features -
for the first time observed by SUMER on disk in full resolution - to
investigate the imprint of the magnetic field on line profile and radiance
distribution. We also compare quasi-simultaneous Ly-alpha and Ly-beta line
profiles. Such high-resolution observations - not hampered by geocoronal
absorption - have never been completed before.
