Yes, its a planetary index but the ground based magnetometers are only in North America with 1 in Fresno, California; if I'm remembering correctly. At any rate, your point is well taken.

There aren't any local magnetometers so that is out of the question. There are some 70 or more miles away, but the data from them isn't available and you really can't trust what they are recording. It seems that everytime somebody notices something going on with either a magnetometer or stress meter or whatever else, the USGS claims that something was wrong with that particular device. --Dennis