Tips on Viewing the Aurora
Being able to see the Aurora depends mainly on two factors, geomagnetic activity (the degree of disturbance of the earth's magnetic field at the time) and your geographic location. Further considerations are the weather at your location, and light pollution from city lights, full moon and so forth.
Geomagnetic Activity -- The Kp Index and the NOAA POES Auroral Activity Level
In order to know whether you have a chance of seeing an aurora, you need to know the level of geomagnetic activity at the time you are viewing. There is a simple index called Kp, a number from 0 to 9, which is used to refer to geomagnetic activity for a 3-hour period. Check the Space Weather Prediction Center's bar plot of Estimated Planetary Kp to see what has been happening during the past couple of days. This plot updates every 3 hours with the latest Kp value. The Space Weather Prediction Center's Solar-Geophysical Forecast for the next 24 hours (see SWPC's Space Weather Enthusiasts dashboard) might also be of help. If the GEOPHYSICAL ACTIVITY FORECAST is for "storm" levels SWPC expects Kp indices of 5 or greater. Another indication of geomagnetic activity is the NOAA POES Auroral Activity Level, which is a number from 1 to 10. Further down on this page is a table that shows how Kp and the Auroral Activity Level compare with each other. Take a look at SWPC's POES Auroral Activity page to see the latest Activity Level. Moon phases can also be found on the web.
Location, location, location!
In general, you are more likely to see an aurora if you are at a high latitude, i.e. closer to the north (or south) pole. However, there is a catch to this. The earth's magnetic poles are not exactly in line with the geographic poles, so the latitude of interest would really be the magnetic latitude. Note that it is not necessary for the equatorward boundary of the aurora to reach all the way down to your magnetic latitude for you to see it. The aurora is easily visible even when its boundary is 4 or 5 degrees poleward of your location. So, how do you know what your magnetic latitude is? We have several methods to help you:
- In the table below, find a city not far from where you live, and make a note of its magnetic latitude.
- Read below about Kp maps (clickable in the future) that will give you the magnetic latitude at a location on the globe.
When geomagnetic activity is low, the aurora typically is located, in the hours around midnight, at about 67 degrees magnetic latitude*. As activity increases, the region of aurora expands toward the equator. When geomagnetic activity is very high, the aurora may be seen at mid and low latitude locations around the earth that would otherwise rarely experience the polar lights.
Kp maps of midnight equatorward boundaries
There are maps for four quadrants of the globe:
The average equatorward boundary of the midnight aurora is shown for levels of magnetic activity ranging from relatively low, Kp=3, to very high, Kp=9. These maps were created using satellite observations to determine the average equatorward boundary of the aurora as a function of the Kp index**. Using those data, the typical maximum extent of the aurora toward the equator for the hours around midnight for four levels of geomagnetic activity is displayed.
* Corrected magnetic latitude
**The Handbook of Geophysics and the Space Environment, Air Force Geophysics Laboratory, 1985
Putting It All Together -- Can I, or can't I, see the Aurora?
Once you know your magnetic latitude, and how high the Kp index needs to be for you to see the aurora at your magnetic latitude, it comes down to choosing a viewing time of high magnetic activity by frequently checking the Kp index and SWPC forecast. The table below shows the relationship between Kp and the Magnetic latitude of the auroral boundary. Of course, for you to see the aurora it will also have to be a clear night without interference from city lights or moonlight.
Additional information about the aurora can be found in the SWPC topic paper on the aurora.