  We used long high-quality unresolved (Sun-as-a-star observations) data
collected by GOLF and VIRGO instruments on board the ESA/NASA SOHO satellite to
investigate the amplitude variation with solar cycle 23 in the high-frequency
band (5.7 < nu< 6.3 mHz). We found an enhancement of acoustic emissivity over
the ascending phase of about 18+-3 in velocity observations and a slight
enhancement of 3+-2 in intensity. Mode conversion from fast acoustic to fast
magneto-acoustic waves could explain the enhancement in velocity observations.
These findings open up the possibility to apply the same technique to stellar
intensity data, in order to investigate stellar-magnetic activity.
