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Geomagnetic variation data with 2.5 minute resolution

1 minute and hourly values reported as definitive from Intermagnet observatories.

Geomagnetic 10 second data provides high temporal resolution of geomagnetic variations

Report on the status of world wide geomagnetic observatories

Geomagnetic Range index using data from multiple observatories - Mayaud 1948

Geomagnetic One Minute Means from world wide observatories

The Geomagnetic Indices Bulletin is a one page sheet containing the magnetic indices Kp, Ap, Cp, An, As, Am and the provisional aa indices. The bulletin is published monthly.

The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) maintains an active database of worldwide geomagnetic observatory data to further the understanding of Earth magnetism and the Sun-Earth environment.Historically, magnetic observatories were established to monitor the secular change (variation), of the Earth's magnetic field, and this remains one of their most important functions. This generally involves absolute measurements sufficient in number to monitor instrumental drift and to produce annual means. Over 70 countries operate more than 200 observatories worldwide. The magnetic observatory data are crucial to the studies of secular change, investigations into the Earth's interior, navigation, communication, and to global modeling efforts. In addition to the continuously operating magnetic observatories, many countries make measurements at temporary magnetic stations (known as repeat stations), over a period of days every 5 - 10 years.The Earth's magnetic field is described by seven parameters. These are declination (D), inclination (I), horizontal intensity (H), vertical intensity (Z), total intensity (F) and the north (X) and east (Y) components of the horizontal intensity. By convention, declination is considered positive when measured east of north, inclination and vertical intensity positive down, X positive north, and Y positive east. The magnetic field observed on Earth is constantly changing.

Yearbook for Italian Geomagnetic Observatories