The 18 mag QSO 1633+382 (4C38.41, z=1.807) showed a very pronounced outburst
in 2001/2002. With a peak amplitude of more than 9 Jy at 90GHz, this flare was
brighter than any known previous flare in this source (data available since
1980).During onset, the mm-flare was particulary fast, with an increase of more
than 2 Jy at 230 GHz in less than 8 days. Since January 2002, the mm-flux of
1633+382 is decaying. During this decline, however, local flux variations with
amplitudes of 1-3 Jy were seen, indicative of underlying and more rapid source
activity on time scales of 1-2 months. After the main peak occurring in
2001.99, the 90 GHz flux showed secondary maxima at approximately half year
intervals in 2002.3, 2002.7 and 2003.13. This kind of periodicity might be
explained via the lighthouse model (Camenzind and Krockenberger 1992), which is
based on the magnetic accelerator of Blanford and Payne (1982). At present the
millimeter flux is nearly back to its quiescent level of 2-2.5 Jy, which the
source had before the flare began. Our VLBA Polarimetry monitoring started June
2002 during the onset of the flare. At cm wavelength, the flare is only
marginally detected which implies very high opacity of the source.Comment: 4 pages. 5 figures. Proceedings of the 7th European VLBI Network
Symposium held in Toledo, Spain on October 12-15, 2004. Editors: R.
Bachiller, F. Colomer, J.-F. Desmurs, P. de Vicente (Observatorio Astronomico
Nacional), p. 85-88. Needs evn2004.cl