... Geomagnetic Indices . ... Minute Values of Geomagnetic Field Components . ... Hourly Values of Geomagnetic Field Components . ... The Earth's magnetic field is described by seven parameters.To measure the Earth's magnetism in any place, we must measure the direction and intensity of the field. ... K indices isolate solar particle effects on the earth's magnetic field; over a 3-hour period, they classify into disturbance levels the range of variation of the more unsettled horizontal field component. ...