This magnetometer section contains data from both the magnetometer in Tromsø and the magnetometer in Reykjavík (Leirvogi). These locations are at latitudes from 69 to 64 degrees north – the Arctic Circle is at 66 degrees north – and allow us to measure aurora activity over a wide area. With these two measurements, it is possible to identify the intensity and also the approximate location of the lights.

Tromsø (69° N): When the Tromsø magnetometer shows increased activity, increased aurora activity can be expected towards the northern (NNE to NNW) horizon. However, weather and atmospheric conditions can affect visibility.

Reykjavík (64° N): Increased readings here indicate northern lights near Iceland, often visible towards the Big Dipper (Ursa Major) (Kp2 to Kp3-4) or directly overhead or towards the southern horizon (Kp4 or higher), when viewed from Reykjavík. The further North you are in Iceland, the better the chances of seeing strong northern lights even with low Kp factors. Staying in the South, you need at least Kp2.

Magnetometer Reading Guide:

Inactivity: Auroras typically become visible when magnetometer readings approach or exceed ±50nT.

Charging Phase: When magnetometers rise above 50nT, it suggests that geomagnetic activity is increasing, and the field is "charging".

Substorm Activity (Active or Very Active): These are usually indicated by sharp drops in magnetometer readings, measuring a decline of 100nT from the starting position or falling below -100nT. Very active substorms will drop well below -250nT and lower.

Weakening Phase: After a substorm, if readings rise from below a negative value, it indicates that the energy is dissipating.

Key Points:

Positive readings above 50nT that are rising generally indicate building geomagnetic activity.

Visibility of the aurora by eye starts from ±50nT, depending on atmospheric conditions, light pollution and other factors.

Readings around or above 100nT suggest auroras might be visible whilst continuing to build energy.

Significant drops below -100nT or sudden changes in readings often signal substorm activity, meaning strong aurora displays.

By monitoring these readings, you can better predict and observe the mesmerizing auroras, whether you're a novice or a seasoned chaser. Always consider local weather conditions and light pollution for the best viewing experience.