At http://www.ann-geophys.net/34/1/2016/ … abstract of a paper by multiple authors from multiple space centres across Europe and the US. These are people looking at the data from the Rosetta Mission (as it is currently understood). It is essentially about the interactions of the solar wind with the outgassing comet Churyumov-Gerasimenko. In June there was an increase in the solar wind dynamic, a burst of energy that struck the comet much like the solar wind sometimes strikes earth's atmosphere full on. What occurred was that the magnetic field aound the comet compressed and the increase in solar wind interacted on the outflow gas via what they call collisional ionisation. These new ions were picked up by the solar wind magetic field and this created a ring or ring-beam distribution which in a high plasma was unstable for mirror mode wave generation. Twin mirror modes were observed. One of small size generated by locally ionised water and one of a larger size generated by ionisation that pushed out further from the comet.
It seems the icy snowball theory is alive and kicking. What is interesting is that the Philae Lander did not detect a sign of a magnetic field on the comet and yet something similar is being invoked in this article. Are they simply talking about the electro magnetic properties of the interaction event?