Aurora looking back at us!

Sometimes you wonder if the sky is staring back at you. Here is a data visualization I have been experimenting with that actually looks like the eye of the aurora:

keogram of aurora activity reprojected in polar coordinates looking like the iris of an eye

These are 'keograms' - a visualization of an entire night from sunset to sunrise, read like a sentence from left to right. You can spot cloudy nights, nights with a bright moon, and nights with aurora activity. 

Keogram is made from a single-pixel-wide slices of an all-sky-camera image. The slices run from the northern to southern horizon, taken at intervals through the night, and stacked left-to-right like the spines of books on a shelf. Here is how a single slice from a single moment of all-sky-camera imagery (from AuroraMAX) is inserted into that bookshelf:

Image of aurora

Here is a little spotter's guide to common features of a keogram

Aurora moving overhead from the north:

An auroral substorm starts in the southern horizon and quickly grows to fills the whole sky before dissipating:

Less common red aurora! These are seen when geomagnetic activity is quite high and are unusual in 2020 when the solar cycle is at a quiet point:

Unfortunately the aurora are above the clouds, so often obscuring clouds can be seen forming:

The bright moon will wash out the dimmer aurora features and appear as a bright slash of white:

During dawn and dusk, the ends of the keogram will start to show the sky brightening:

I've put together a demo web application that lets you explore years with of the Yellowknife night sky and aurora at a glance using the 'magic' of keogram spotting:

It is quite easy to spot clouds, aurora, moonlight and auroral substorms when all the keograms for many nights are stacked:
a stack of keograms of sequential nights More reading The AuroraMAX website, an amazing resource with years of all-sky-camera imagery from Yellowknife:

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