Aurora Borealis Pocket Guide

ssd drive

Photo by Serey Kim on Unsplash

Wednesday, July 12th, 2023, was supposed to feature high solar activity, allowing for an incredibly large area of the northern United States to witness the Auroras as long as the light pollution was low enough.

Solar activity stayed at normal levels, so only the usual locations were able to see the lights, causing me to cancel my plans. Nevertheless, I wanted to share them here.

Light Pollution

Take a look at these locations sorted by distance.

Location Distance Travel Time Rank*
Minneapolis 16 miles 25 minutes 0
Bloomington 2 miles 5 minutes 1
Chaska 15 miles 20 minutes 2
Farmington 24 miles 35 minutes 3
Jordan 22 miles 25 minutes 4
Norwood 35 miles 40 minutes 5
Gaylord 55 miles 60 minutes 6
Rapidan 75 miles 75 minutes 7
Chengwatana 95 miles 90 minutes 8
Sacred Heart 105 miles 120 minutes 9

* Higher Rank is considered better.

Tips to Get a Better Look

Viewing the aurora depends on four important factors.

1. Geomagnetic Activity

If the geomagnetic field is active, then the aurora will be brighter and further from the poles. Geomagnetic activity is driven by solar activity and solar coronal holes and thus it waxes and wanes with time. The level of geomagnetic activity is indicated by the planetary K index or Kp. The Kp index ranges from 0 to 9.

It should be noted that the relationship between Kp and auroral latitude are approximate and represent averages. There will be times when these relationships do not hold up exactly.

There is an approximate relationship between Kp and the equatorward extent of the auroral oval. This relationship holds true in geomagnetic latitude, not geographic. At Kp = 0, the equator ward edge of the auroral oval is approximately 66 degrees. And it moves equatorward about 2 degrees for each level of Kp. So for Kp = 1, the aurora would move down to 64 degrees, for Kp=2, it would move to 62 degrees, etc… until reaching Kp of 9 at 48 degrees magnetic latitude.

2. Location

Go towards the magnetic poles. The north magnetic pole is currently about 400 km (250 miles) from the geographic pole and is located in the islands of north east Canada. Find a place where you can see to the north ( or south if you are in the southern hemisphere). Given the right vantage point, say for example on top of a hill in the northern hemisphere with an unobstructed view toward the north, a person can see aurora even when it is 1000 km (600 miles) further north. It should be noted that if you are in the right place under the aurora, you can see very nice auroral displays even with low geomagnetic activity (Kp = 3 or 4).

3. It Must Be Dark

Go out at night. Get away from city lights. The full moon will also diminish the apparent brightness of the aurora (not the actual brightness). One caveat that people often neglect to think of is that the high latitudes where aurora occur are also latitudes where it doesn't get dark in the summer. So combining a summer vacation to the arctic with aurora watching usually doesn't work. The aurora may still be there but it is only visible when it is dark.

4. Timing

Best aurora is usually within an hour or two of midnight (between 10 PM and 2 AM local time). These hours of active aurora expand towards evening and morning as the level of geomagnetic activity increases. There may be aurora in the evening and morning but it is usually not as active and therefore, not as visually appealing.

The best Seasons for aurora watching are around the spring and fall equinoxes. Due to subtleties in the way the solar wind interacts with Earth's magnetosphere, there is a tendency towards larger geomagnetic storms, and thus better auroras, to occur near the equinoxes. However, the number of hours of darkness decreases (increases) rapidly near the spring (fall) equinox so this caveat must be considered for those traveling to see the aurora.

Below are maps showing the most southern extent of where aurora might be observable for different levels of the geomagnetic Kp index (and the NOAA G scale). It should be noted that the aurora can often be observed hundreds of kilometers (miles) equatorward of the actual aurora so these figures do not indicate where the aurora may be but rather the point from which it may be observed.

Aurora Forecast

July 12th, 2023

NOAA Space Weather Prediction Center - G-Kp G is NOAA Geomagnetic Storm Index (0–5)
Kp is Planetary K Index (0–9)

September 18th, 2023

aurora forecast for 2023-09-18

Additional Resources