Unexpected Aurora

Rays from an Unexpected Aurora

This aurora was a bit of a surprise. For starters, on this Friday morning in August 2002, no intense auroral activity was expected at all. Possibly more surprising, however, the aurora appeared to show an usual structure of green rays from some locations. In the above image, captured from North Dakota, USA, a picket fence of green rays stretches toward the horizon. Mirroring the green rays is a red band, somewhat rare in its own right. Lights from the cities of Bismarck and Mandan are visible near the horizon. Large sunspot groups indicate that activity from an active Sun is relatively likely, possibly causing other streams of energetic particles to cascade onto the Earth and so causing more auroras.

Aside from being very beautiful, it's spooky that they would be striated that way.

OK, as I understand it, auroras are only visible because particles hit our atmosphere at a certain angle and because of how they are influenced by the earth's magnetic field.

What would account for this surprise aurora- both in timing and shape?

It bugs me that this aurora is represented as unique and unexplained....

Is something changing in the earth's atmosphere or magnetic field? What is causing those striations????