Large amplitude, low frequency plasma fluctuations at Comet Giacobini-Zinner

Very large amplitude fluctuations in electron density, temperature, and flow velocity were a prominent aspect of the solar wind interaction with Comet Giacobini-Zinner during the ICE encounter in September 1985. These fluctuations were detected at a distance of at least 900,000 km and grew in amplitude as ICE approached the comet, peaking in amplitude 60,000 km from closest approach. A typical period associated with the fluctuations was about 2 min, which corresponds to a scale length in the solar wind frame of about 50,000 km. For the most part these fluctuations appear to be a product of one or more plasma instabilities associated with the solar wind pick up of cometary ions.