Time series of (a): simulated cometocentric distance of a spacecraft flying past a comet at 40 km s⁻¹ with a closest approach of 1000 km, (b): observed ionospheric density along this track, if assuming symmetric out-gassing and a 1/r distribution, (c): density at a fixed point at R = 1000 km if a sinusoidally varying outgassing is introduced due to a rotating in-homogeneous nucleus, (d): along-track observed ionospheric density for a sinusoidally varying outgassing, (e): density at a fixed point at R = 1000 km if a sawtooth-like varying out-gassing is introduced, (f): along-track density for the sawtooth variation in outgassing.