AuroraSeeGuide
Kp vs Kaus, explained
Two different geomagnetic indices, and they don’t always agree. Here’s what each one actually measures.
Written by the AuroraSee team · Brisbane, Australia · Updated 29 July 2026
What is Kp?
NOAA’s planetary K-index, on a scale of 0 to 9, averaged every 3 hours from 13 geomagnetic observatories spread around the world. It’s the number every aurora app leads with, but it’s a global average, and most of those stations sit in the northern hemisphere. A storm can register very differently depending on which side of the planet it’s actually strongest over.
What is Kaus?
The Australian Bureau of Meteorology’s own K-index, computed from magnetometers at Alice Springs, Canberra, Cocos Island, Darwin, Hobart, Learmonth and others, plus Antarctic bases at Casey, Davis, Mawson and Macquarie Island. It measures geomagnetic disturbance directly over the Australian sector, which is why it’s the number chasers in Tasmania and Victoria actually trust, and why it can read higher (or lower) than the global Kp on the same night.
Which one should I watch?
Kaus, if you’re in Australia: it’s the regional read. We show both, and our storm alerts trigger on Kaus, sustained southward Bz, or a live BOM aurora alert, not on Kp alone.