Magnetometer
Definition
An instrument measuring the strength and direction of magnetic fields — the workhorse of aurora monitoring.
In plain language
Ground stations worldwide run sensitive magnetometers that twitch when auroral currents flow overhead. Their combined readings become the Kp index; a jumpy local magnetometer trace often means aurora above that station right now.
The science
Fluxgate magnetometers resolve nanotesla-level variations. Ground arrays detect auroral electrojet signatures; the same principle aboard L1 spacecraft measures the IMF that feeds real-time forecasting.
Why it matters for aurora viewing
Local magnetometer charts are an underrated nowcasting tool: sharp deflections at a station near you frequently coincide with visible displays.
See this in action on tonight's data.