Magnetic Latitude
Definition
Your latitude measured from the magnetic pole rather than the geographic pole — what actually determines your aurora odds.
In plain language
The magnetic pole isn't at the geographic pole, so two cities equally far north can have very different aurora chances. Minneapolis outperforms much of Europe at the same geographic latitude for exactly this reason.
The science
Geomagnetic coordinates are defined relative to the geomagnetic dipole/field model. Auroral occurrence organizes by magnetic latitude; North America sits magnetically poleward of geographically comparable Eurasian longitudes.
Why it matters for aurora viewing
Convert your location to magnetic latitude once and your personal Kp threshold becomes far more accurate than any geographic rule of thumb.
See this in action on tonight's data.