  The high-quality, full-disk helioseismic observations continuously collected
by the spectrophotometer GOLF and the three photometers VIRGO/SPMs onboard the
SoHO spacecraft for 17 years now (since April 11, 1996, apart from the SoHO
"vacations") are absolutely unique for the study of the interior of the Sun and
its variability with magnetic activity. Here, we look at the differences in the
low-degree oscillation p-mode frequencies between radial velocity and intensity
measurements taking into account all the known features of the p-mode profiles
(e.g., the opposite peak asymmetry), and of the power spectrum (e.g., the
presence of the higher degrees l= 4 and 5 in the signal). We show that the
intensity frequencies are higher than the velocity frequencies during the solar
cycle with a clear temporal dependence. The response between the individual
angular degrees is also different. Time delays are observed between the
temporal variations in GOLF and VIRGO frequencies. Such analysis is important
in order to put new constraints and to better understand the mechanisms
responsible for the temporal variations of the oscillation frequencies with the
solar magnetic activity as well as their height dependences in the solar
atmosphere. It is also important for the study of the stellar magnetic activity
using asteroseismic data.
