Northern Lights Forecast: Why Aurora Strength Matters

What is Aurora Strength?

Aurora Strength on Hello Aurora is a real-time measurement of how active the aurora is based on ground-based magnetometer readings. The number is measured in nanoteslas (nT).

Aurora Strength is different from the Kp index in an important way, such as it captures short-term, localized magnetic disturbances.

On Hello Aurora, the forecast updates every few minutes based on your geo-location, instead of using the KP index, which is a delayed 3-hour global average.

How it works

When solar wind interacts with Earth, electric currents flow through the upper atmosphere of Eartt's magnetic field. These currents create the Aurora Borealis or the Northern Lights while disturbing magnetometers at ground level.

When the aurora becomes active, the electrical currents flowing through it disturb Earth's magnetic field and detected by Magnetometers, the sensitive instruments scientist placed at various ground stations to measure the geomagnetic storm (e.g., across Nordic countries, the UK, Canada).

As for Hello Aurora we, check your location and find the closest ground station that detect these current closest to your location. That's how we are able to track the Northern Lights intensity above you in real-time.

How to read Aurora Strength numbers

Understanding the numbers takes just a few seconds.

The further the number drops below zero, the brighter and more dynamic the Northern Lights become. For example, a drop past -150 nT signals a high activity level, with the aurora expanding across the sky. At this time, you will receive the "Substorm is expanding" notification from Hello Aurora. Based on the Aurora Strength you will receive more intense alerts notifications.

On the other hand, positive numbers can mean energy is building up: for instance, a positive number like 150 nT may mean the magnetic field is charging. However, just because energy is charging up doesn't guarantee it will trigger a substorm. The best approach is to check this metric alongside other real-time indicators, such as the Bz component and Solar Wind Speed.

Why is Aurora Strength the core metric for Northern Lights hunting?

Because it captures short-lived aurora activity better than any other metric.

You may see other aurora forecast tools suggesting that a high Kp index means a strong chance of seeing the lights. The truth is, that is not accurate. Again, the Kp index is a 3-hour average on a global scale and can completely miss short-lived activity.

Aurora Strength on Hello Aurora captures these brief displays and updates every few minutes from the source closest to your location.

Quite often, the Kp index seems impressive at a high 5 or 6, but with a weak (positive Aurora Strength) people do not see anything because they are focusing on the wrong metric.

Another fun thing to check is Moment, our feature for real-time photo sightings. You can see how strong the Aurora Strength was when a user shared their photo.

Most of the time, you will notice that intense, vibrant aurora photos happen when the Aurora Strength reaches its negative nanotesla reading.

Aurora Strength notifications

If seeing the Northern Lights is your goal, you will not want to miss when a substorm expands.

On Hello Aurora, we send notifications to users when the Aurora Strength reaches negative levels where a substorm may form.

Pro users can filter these alerts to get substorm notifications at a specific level. For example, only when a substorm is strong—so you never miss a great show.

Frequently asked questions

Q: Why does Aurora Strength give the most accurate Northern Lights forecast?
A: The Kp index can easily mislead you. A high global Kp index of 5 or 6 can sit alongside a completely dark sky if the local magnetic field is quiet. Hello Aurora matches your GPS coordinates to the nearest local magnetometer station. Instead of relying on a delayed planetary average, you get real-time data for the exact field you are standing in.

Q: Is Aurora Strength the only metric that guarantees my chances?
A: No, Aurora Strength only tells you how active the lights are. Substorms can happen during daylight too, and if your sky is cloudy or there is too much light pollution, your chances to see the Northern lights will still be slim. Use Aurora Strength along with cloud coverage, Bz, and local weather conditions.