Once again we find ourselves in a pattern with the possibility of seeing the aurora borealis. As you may know, this is a very very difficult thing to forecast and makes predicting a snowstorm look easy.
There are some reasons to be optimistic about seeing the aurora. NASA’s latest forecast does indicate a chance of a storm level geomagnetic activity during the next few days. This activity would charge the atmosphere enough to bring an appearance of the aurora into New England. How far south they would appear is nearly impossible to predict.
In the shorter range, on the order of hours, the level of activity is better predicted, but it’s still not perfect. The number I used to watch for the aurora is the Kp-index. This number is available on the internet and I tweet it @growingwisdom when it is predicted to be higher than 5. The Kp-index is the global geomagnetic storm index and is based on 3 hour measurements of the K-indices, for a given value, for each of the past days.
The map below shows how the Kp index is used. Notice the Kp number lines running higher as you move further south. These lines represent a good idea of the southern extent of the predicted aurora. It’s not impossible to see them if you live south of the line of the current index, but they will be low on the horizon.
For example, if the Kp number hit 7, most of northern and parts of southern New England would, if it was clear and dark, see the aurora. The most likely scenario is the Kp-index reaches 5 or 6 tonight at some point. This means some of you in northern Vermont, New Hampshire and Maine have the best chance of seeing the display.
Maybe we will luck out this time.