I thought I would share some tips for photographing the aurora borealis, also known as northern lights. The hardest part of photographing the auroras is finding them – so today I thought I would write about finding them, tomorrow actually photographing them.
Generally speaking, the further north, the better your chances of seeing the aurora. The best time of year tends to be close to the equinox (March and late September – October). This time of year also offers enough darkness in the northern regions without the temperature extremes you often find in winter. Summers in the north don’t offer enough darkness to see the aurora. Midnight local times also seems to be the best time for viewing, but a big solar storm can hit pretty much any time of day or year, so you always want to be ready. A place like Fairbanks, Alaska can be a great spot if you are serious about seeing the aurora, I believe they see them something like 70% of the time. I know where I grew up in Glennallen they were a regular occurrence. Seeing them in Seward is much tougher, we are a little too far south and west of the typical aurora oval, not to mention we often have cloudy weather. When the conditions are right, you can see them in the lower 48 even as far south as Arizona.
Aurora borealis activity is usually proceeded by some type of solar event. Because of this, the chance of an aurora display can often be predicted a few days in advance. There are two sites I usually check for aurora forecasts. The Geophysical Institute at the University of Alaska Fairbanks offers hourly, daily and monthly forecasts. Spaceweather.com also provides forecasts, photos and other information on auroras, along with interesting information about other space phenomena.
Now that you know that auroras are in the forecast, where and when will you actually see them? Predicting the aurora borealis seems a little like predicting weather, there are some good indicators, but nothing is perfect. One of the most important things to watch for is the Kp-index. I won’t get into a lot of details into what this number represents (because I don’t really know) but what I do know is that the higher the number the better. Where I live just north of Latitude 60, I typically need to see a Kp of 5 or higher. In the lower 48, you may need 6, 7 or higher for success. By the way last Thursday hit 8.
There are a number of websites that provide Kp readings, but since most people live in places where auroras aren’t a regular occurrence, monitoring aurora activity isn’t usually a priority. There is a great solution; a free subscription to the Auroral Detection and Early Warning System (ADEC). This free service will send you an alert (via email, pager or mobile phone) whenever the Kp exceeds a predetermined level. In the subscription form, there is a place where you can enter your latitude and longitude to help determine what Kp level you need to see aurora in your area. Then when the Kp reaches your predetermined level, you get an email – this is very handy.
If you want to get a little more advanced, there are a couple of other figures I watch. I try to keep an eye on the solar wind speed and the direction of the magnetic field. The wind usually picks up during a solar storm, and figures over 500 km s-1 are usually an important indicator. Last Thursday the wind pegged the top of the scale at 1,000 – that is fairly unusual, but certainly an indicator of something special.
The other important statistic is the direction of the magnetic field. This must be pointing southward. It seems like no matter how much wind there is, if the magnetic field isn’t pointing south, there won’t be much aurora activity.
So where do you get these readings? The Space Environment Center has an easy to read display that looks like a dashboard, this can be monitored with a quick glance. When the weather is clear in Seward and the aurora forecast is favorable, I drop by this site to check on the current weather regularly. Spaceweather.com also provides wind speed and magnetic field direction in the left hand column of their homepage.
When all indicators are looking good, I monitor this page at the STD Aurora Monitor as it gives me real-time views from space of the current Aurora activity along with actual sightings by followers. When these images are lighting up, it is time to hurry outside if I’m not there already! Tomorrow – how to photograph the aurora.