I subscribe to NOAA Space Weather Alerts, because….. This is what came across this morning, an alert of K-7, which is pretty high on the scale and considered a STRONG storm.
I use a couple of sites to see what is going on after receiving an alert:
For Further information about the K-index, SWPC provides a short summary of it’s characteristics, and please visit the official Kp index web page(link is external) at the German Research Centre for Geosciences (GFZ).
The K-index quantifies disturbances in the horizontal component of earth’s magnetic field with an integer in the range 0-9 with 1 being calm and 5 or more indicating a geomagnetic storm. It is derived from the maximum fluctuations of horizontal components observed on a magnetometer during a three-hour interval. The planetary 3-hour-range index Kp is the mean standardized K-index from 13 geomagnetic observatories between 44 degrees and 60 degrees northern or southern geomagnetic latitude. The label ‘K’ comes from the German word ‘Kennziffer’ meaning ‘characteristic digit.’ The K-index was introduced by Julius Bartels in 1938. SWPC has used the K-index since the forecast center began operations.