Can aurorae/northern lights be used as an energy source? Their temperature is high, they have high velocity. Can they be used as an source of energy? If not why? If yes how?
 A: It would be very inefficient to do so.
A good measure of the power you could extract is the pressure exerted by the solar wind (which is the source of Northern lights). According to this wikipedia article, the pressure is on the order of 1 - 6 nPa (nano pascals). Multiply this by the velocity of the solar winds (up to 750 km/s - same source) to get the power: about 5 mW per square meter.
Compare this to the power of sunlight on earth - around 1 kW per square meter - and add the difficulty of collecting the power of the Northern lights (altitude) and you can see it would not be a good idea.
Another way to look at this: you can only see the Northern lights at night. There's another, much brighter source of energy that you can see even in daylight. That's obviously going to be a better choice.
A: The Aurora Borealis occurs in the thermosphere above the North Pole. 
The space station orbits on the edge of thermosphere which is part of the ionosphere.
It would be extremely difficult if not impossible to harness the light or the electrical current which causes the light since they're dispersed over a huge area. 
At that altitude over the pole it would be far more efficient to use solar panels. 
A: Using the northern lights as an energy souce would be great, the energy created by the nuclear fusion happening which emits the glow, is substantial. However the energy output is only greater than the output at a certain temperature and pressure (which is the peak of the emmited light) and then as it hits surrounding matter, the surrounding matter cools the gases so they are no longer a plasma form. However if we could somehow create that same effect in a vacuum, using immense magnetic fields to control the plasma within the vacuum, we hypothetically could have a stable, never ending energy source. Sort of like a more stylish controlled mini sun. This is also hightimes speaking. JEH
