From Gardner's comments on the aurora:
IS IT CONTINUOUS?
Greely in his " Three Years of Arctic Service " says a number of interesting things. He remarks that there is always a feeble auroral light even when there is not a brilliant display. Soon after that remark we find him observing a perfectly circular aurora which he calls a mock sun. It had burning colors of blue, yellow and red with bars of white. A few days after, he witnessed an aurora which had a beautiful corona or crown of light around it. It had numerous and brilliant streamers. Then here is another description of an aurora:
" A beautiful and brilliant arch about three degrees wide, formed of twisted, convoluted bands of light, similar to twisted ribbons, extended from the southwest through the zenith to the north-eastern, horizon. Occasionally, well-marked and clearly defined patches of light detached themselves, as puffs of smoke from a pipe, and drifted fading to the north west. The arch seemed to be continually renewing itself from the southwest to fade at the opposite end. Perhaps a better idea of this peculiar formation may be conveyed by likening the display to an arch having the appearance of an endless, revolving screw. This formation was by no means infrequent, but I have never seen it elsewhere or known it to be described."
List Members-
There is always at least a minimum flow of soft particles emanating from the polar opening, so there is always at least some break-up of those particles into visible photons, and therefore, at least a faint aurora is always present.
The above comments by Lt. Greely to this effect are instructive.