12-hour Boulder-USGS Magnetometer Monitor with 3-hourly K-Indices

Final Boulder K-indices are available at Geomagnetic and Solar indices, A/K Indices lists, and the Geophysical Alert Message (WWV)

SWPC Space Weather Alerts for geomagnetic phenomena are based primarily on real-time data from the Boulder-USGS magnetometer, which is used as a proxy for mid-latitude locations, and as a general indicator of the trend in USAF Planetary K-indices that are not available in real-time.

The geographic location of the Boulder-USGS geomagnetic observatory is N40.1 W105.2. Magnetometer values are the average of 60 1-second samples. The H component is directed along magnetic north, which is currently about 10 degrees east of geographic north. The D component is pointing 90 degrees clockwise relative to H. This is currently about 10 degrees south of geographic east. For more information see The K-index.