Principal Magnetic Storms - These data present the principal magnetic storms for the month as reported by several observatories through cooperation with the International Association of Geomagnetism and Aeronomy. ... The geomagnetic latitude of the station is indicated. The beginning time is given to the hour and minute in UT. ... In the next columns the day and the three-hour periods on that day when the K index reached its maximum are given followed by the K index value. ...