Dayside pulsed aurora intensifications, observed by ITACA during constant IMF Bz ~ 0 and By << 0

On November 30th, 1999, the Italian all-sky camera ITACA (Ny-Ålesund, Svalbard), observed one of the strongest dayside aurora events occurred during the 1999/2000 winter season. In the postnoon, the red auroral activity was characterized mainly by four quasi-periodic pulsed activations, with brightness, period and latitudinal extent increasing monotonously with time. During this period, the WIND satellite was well positioned upstream in the solar wind and measured a IMF Bz close to zero, together with a constantly negative IMF By ~ -10 nT. A detailed description of the phenomenon is presented, together with a preliminary analysis of the data. This work underlines that it is difficult to identify, among the parameters usually involved in the solar wind – magnetosphere coupling, the source of the modulation(s) observed in the aurora development.