INTERMAGNET

Connecting the observatories

Magnetic observatories had existed since Gauss and Weber's day, but their records arrived on paper, years late. At a workshop in Ottawa in 1986 the exchange of data in digital form was seriously discussed; in 1987 the British Geological Survey and the US Geological Survey presented a pilot scheme at the IUGG General Assembly in Vancouver. A pilot among the United Kingdom, the United States and Canada was a success in 1989, and the International Association of Geomagnetism and Aeronomy endorsed INTERMAGNET.

The first Geomagnetic Information Node was established in 1991, and the first CD-ROM of data was published that year. Information nodes now operate in several countries and give a mirror of the data.

Membership by standards

An institute can join INTERMAGNET by operating an observatory to the network's technical standards: the instruments, sampling rate, baseline control and reporting. The institutes still own and run their observatories; INTERMAGNET sets the standard, collects the data and publishes them. The standards cover instruments, absolute measurements and timing, and a certification process tests whether an observatory meets them.

The product is a continuous record of the Earth's magnetic field from observatories around the world, used for space-weather warnings, navigation models, geophysical surveys and research.

Today

The network brings together more than a hundred observatories from over forty countries. An Eos article in 2022 described modernising the partnership, including one-second data and a path for new members. The data are released under licence terms that do not allow commercial use, so Nexus Observatory does not republish them; this page describes the organisation only.

Open to some, not to all

The network's data policy balances the interests of the institutes that produce the data with the interests of users who want them freely. The data are freely available for non-commercial use and licensed under conditions that restrict commercial redistribution. That is a legitimate choice for a membership organisation, and it is also the reason that the data are not republished in this atlas. A product built on a data source must respect its terms, and the sensible way to do so is to read the licence before building and to choose alternatives, such as national geomagnetic services with open terms, when a source's terms do not fit.

Instruments and technologies

• Fluxgate variometer A three-axis fluxgate magnetometer records changes in the field continuously.
• Absolute instruments A theodolite with a fluxgate sensor measures the absolute declination and inclination, and a proton magnetometer measures the total field, to set the baseline of the variometer.
• Geomagnetic Information Nodes Servers that collect and distribute the data to users.

Timeline

• 1986 Data exchange first seriously discussed at a workshop in Ottawa.
• 1987 BGS and USGS pilot scheme presented at the IUGG General Assembly in Vancouver.
• 1989 Successful pilot among the UK, USA and Canada; IAGA endorses INTERMAGNET.
• 1991 First Geomagnetic Information Node established and first data CD-ROM published.

Key lessons for observation today

• Membership by standards works Institutes keep their observatories and agree to the same standards. A federation holds together by a rule book, not by ownership.
• Baselines make the data absolute Absolute measurements calibrate the continuous record. Every continuous sensor needs a reference measurement.
• Read the licence The data are released for non-commercial use. A data source's licence decides what a product can do with it, and it belongs in the register with the data.

Sources

• INTERMAGNET, home page
• INTERMAGNET Technical Manual, History and status
• Eos, Modernizing a global magnetic partnership