Schematic illustration of a flyby through a coma where the comet is rotating with a period of 2 days and the outgassing is not constant over the surface. The black spiral indicates the maximum density, i.e. a phase-front, of the cometary plasma formed as the comet is outgassing (with a neutral and plasma velocity of 1 km s⁻¹) and rotating. The spiralling pattern is shown for 10 days of rotation, and will at some distance be smeared out by solar wind variations. The spacecraft is assumed to pass by at 40 km s⁻¹ and takes about 12 h to cross this shown area.