The NOAA Space Environment Center has indicated a 20% chance of an aurora at our latitude over night tonight (August 4th into the 5th). The first space weather event occurs at 6pm mountain time and could still be in progress as darkness falls. The second event will occur at around midnight, possibly sparking aurora in the early hours of the morning. Best chance for sighting is to go to a reasonably dark location away from cities if possible, and look northwards. If an aurora is occurring, you may be able to see a red or green glow on the northern horizon. I suggest keeping an eye on www.spaceweather.com for updates as the evening continues.
The Sun has periodic explosions of material on its surface which we call Solar Flares. These flares can sometimes lift highly charged material off the surface of the Sun and into space, and event called a Coronal Mass Ejection (CME). CMEs generally take about 3 days to travel the distance between the Sun and Earth’s orbit. If this happens to occur while pointed towards the Earth, it can cause several different effects, one of which is the Aurora Borealis (and Aurora Australis in the southern hemisphere). Auroras occur because the charged particles in the CME interact with our Earth’s magnetic field and our atmosphere. Particles in the atmosphere can begin to emit light, or glow, due to this interaction.
There is no danger to observers on the ground, though some other effects of arriving CMEs can be harmful if precautions are not taken. NOAA (National Oceanic and Atmospheric Administration), and more specifically the Space Environment Center, is primarily responsible for monitoring the space environment and issues alerts. These alerts allow satellite and utilities companies to take precautions with their hardware. Airplane flights over the polar regions of the Earth will also divert to protect passengers. And Space Shuttle and Space Station astronauts take cover in special areas of their spacecraft in order to be sheltered from the CME’s effects. A lot of study and monitoring goes into making sure that we are kept safe from these frequent “burbs” from the Sun.