Aurora coming up: find a dark sky.

On the nights of July 16-17 and 17-18, chances of seeing the aurora near Seattle are quite good; Sunday night will be clear, Monday night, partly cloudy.

Skyline’s 26th Floor Observation Deck has more than the usual amount of city lights, though it is worth a try; take a hat that can block lights to your left.  There are places within Seattle (zoom in to see) that veteran aurora watchers recommend for stargazing in general but remember that you want a good view of the northern sky for the aurora, such as Green Lake:

The 35th Ave SW hilltop in West Seattle ought to have good northern views from side street.  The park is open until 1130pm to get even farther away from streetlights.

This description of an evening’s light show, from NOAA’s space weather:

Often the auroral forms are made of many tall rays that look much like a curtain made of folds of cloth.  During the evening, these rays can form arcs that stretch from horizon to horizon.  Late in the evening, near midnight, the arcs often begin to twist and sway, just as if a wind were blowing on the curtains of light.

At some point, the arcs may expand to fill the whole sky, moving rapidly and becoming very bright.  This is the peak of what is called an auroral substorm.

Then in the early morning the auroral forms can take on a more cloud-like appearance.  These diffuse patches often blink on and off repeatedly for hours, then they disappear as the sun rises in the east.

If you are curious about the physics:

The Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights) are the result of electrons colliding with the upper reaches of Earth’s atmosphere…. [They come from a storm on the sun that ejects electrons which take three days to reach the Earth’s magnetic field.]  The accelerated electrons follow the magnetic field of Earth down to the Polar Regions where they collide with oxygen and nitrogen atoms … in Earth’s upper atmosphere.  In these collisions, the electrons transfer their energy to the atmosphere thus exciting the atoms and molecules to higher energy states.  When they relax back down to lower energy states, they release their energy in the form of light.  This is similar to how a neon light works.  The aurora typically forms 80 to 500 km above Earth’s surface.

Earth’s magnetic field guides the electrons such that the aurora forms two ovals approximately centered at the magnetic poles.  During major geomagnetic storms these ovals expand away from the poles such that aurora can be seen over most of the United States.

A big mass ejection was observed on July 14, thus the prediction for the nights of July 16-18.