PROBING 5-MINUTE OSCILLATIONS IN THE SOLAR-WIND WITH COMET HALE-BOPP (C 1995 O1)/

This study aims at short-period fluctuations of the solar wind by usin g comet Hale-Bopp (C/1995 O1) as a probe. The comet's intensity fluctu ations due to changes in the reflectivity and emission of molecular li nes are investigated both in the coma and the tails at about 1 AU heli ocentric distance. The existence of oscillations with periods of a few minutes as an already suggested by Isserstedt & Schlosser (1975) on t he basis of observations of comet 1973f (Kohoutek). We focus here on t he time scale of the solar p-modes (5 min.); Thomson et al. (1995) hav e recently claimed to observe these periods in the flux density of the solar wind. Both in the comet's coma and in the ion tail we found osc illations on the time scale of minutes if mainly the stimulated emissi on of the C-3 line was observed through a 'narrow-band' filter. No com parable oscillations were seen through a 'broad band' filter where ref lected sunlight dominates the intensity. We show that the observed flu ctuations are neither induced by the earth's atmosphere nor due to gen uine comet activity.