I don't get really why this is so surprising. The planet Venus has had cometary plasma tails, as has Mars (and it is entirely possible that the age old religiou

I don't get really why this is so surprising. The planet Venus has had cometary plasma tails, as has Mars (and it is entirely possible that the age old religious tales of Mars being some sort of warrior, and Venus being an angry snake-headed goddess was just our ancestors witnessing a very rare interplanetary electrical discharge via Birkeland currents), so this is probably just a form of our own tail. Aurora themselves are just the interaction of our magnetic field with that of the Sun's, so it seems unlikely that large scale magnetic fields are not also the cause of this one.