Comet Ion Tail Observations Far From the Nucleus

Sammanfattning: On may 1, 1996, Ulysses spacecraft crossed the ion tail of comet Hyakutake, revealing an ion tail length of more than 3 times the Sun-Earth distance. The signatures of an ion tail, especially the ion tail far from the nucleus, are not well explored and many question marks remain. This report summarizes previous observations of spacecraft - ion tail crossings and what signatures that can be expected, as well as signatures of other known solar wind structures. A data analysis is made of possible ion tail encounters from Rosetta spacecraft measurements, Ulysses spacecraft measurements and Earth-orbiting spacecraft measurements. A search from Venus Express data to detect ion tails of sungrazing comets is presented.