On 29 July, Rosetta observed the most dramatic outburst yet, registered by several of its instruments from their vantage point 186 km from the comet. They imaged the outburst erupting from the nucleus, witnessed a change in the structure and composition of the gaseous coma environment surrounding Rosetta, and detected increased levels of dust impacts.
Perhaps most surprisingly, Rosetta found that the outburst had pushed away the solar wind magnetic field from around the nucleus.
... “Usually, the jets are quite faint compared to the nucleus and we need to stretch the contrast of the images to make them visible – but this one is brighter than the nucleus.”
Comet’s firework display ahead of perihelion
At the end of July 2015 there was captured a dramatic jet (electrical discharge?) from the comets surface.
The jet was very short lived, only a few minutes, yet its effect on the comets electromagnetic environment (magnetosphere/plasmaphere?) was very very surprising and seemed to last for a few days.
How could one very short but dramatic discharge of what is said to be a water/ice jet effect the local plasma environment around it for so long?