LAN2 alert issues

The magnetometer located near Lancaster University, known as LAN2, is currently experiencing an issue with one of its sensors. While investigations are underway, we have temporarily removed LAN2 from the list of AuroraWatch UK alert sites. The data from LAN2 is still available on our website but our alert system will not use its data to issue alerts.

The issue appears to be affecting the measured magnetic field in the horizontal (H) component only. It seems that the gain on the sensor has changed, with readings being consistently higher than previous. The jump first appeared on Sunday morning and has been consistently higher than we would expect based on the current quiet day curve.

The issue is only present in the H-component, suggesting a fault/unexpected behaviour in that sensor rather than local interference (which would affect all three magnetic field components). Our quiet day curves cannot account for this jump at this point, as they are updated monthly using the quietest five days in a calendar month (more info here). Although the sensor is still measuring changes in the magnetic field correctly, the relative level of geomagnetic activity we calculate from it (i.e. measured magnetic field value minus the quiet day curve) is incorrectly offset causing the alert level to be higher than it should be.

We will update you when the issue has been resolved and LAN2 is added back to the alert list.