Abstract
Results from narrow-band photoelectric photometry of comet Halley after its perihelion passage are presented. The mean atmospheric extinction coefficients determined at Bosque Alegre for six bands between 3600 and 5200 Å are consistent with those of the UBV and DD0 systems. The largest fluxes measured successively correspond to the molecules of C2 , CN, and C3 . The CN emission is typically 70% of the one C2, while the one of C3 is about 20% . The observations show that : (i) There is no detectable contribution of molecular ions CO+ during the period in consideration. (ii) Between March 15 and 22 of 1986 there is a decrease in the proportion of molecules of C2,CN,andC3, with respect to the presence of dust indicate by the continuum. Similar decreases, observed with a P = 6d.1 ± 0d.2, coincide with disconnection events detected from Bosque Alegre and other observatories. If they correspond to the frequency of passage of magnetic solar sectors by the comet, a solar "synodic" rotation Pc = 4P = 24d.4±0d.8, with respect to the comet, is deduced. This value is in excellent agreement with the mean value of the apparent solar rotation with respect to the comet.
