International Real-time Magnetic Observatory Network
The International Real-time Magnetic Observatory Network is a world-wide consortium of institutes operating ground-based magnetometers recording the absolute level of the Earth's time-varying magnetic field, to an agreed set of standards. INTERMAGNET has its roots in discussions held at the Workshop on Magnetic Observatory Instruments in Ottawa, Canada, in August 1986 and at the Nordic Comparison Meeting in Chambon La Foret, France, in May 1987. A pilot scheme between USGS and BGS was described in the sessions of Division V of the International Association of Geomagnetism and Aeronomy at the 19th General Assembly of the International Union of Geodesy and Geophysics in Vancouver, Canada, in August 1987. This scheme used the GOES East satellite to successfully transfer geomagnetic data between the two organisations. INTERMAGNET was founded soon after in order to extend the network of observatories communicating in this way. 62 different institutes are now members of the INTERMAGNET consortium, and, since 1991, data have been contributed to INTERMAGNET from approximately 150 observatories. INTERMAGNET is a member of the World Data System of the International Science Council, and it is closely associated with the International Association of Geomagnetism and Aeronomy.
INTERMAGNET is organised into an Executive Council, formed of representatives of its founding members, and an Operations Committee, formed of members from many institutes concerned with geomagnetism and with operating magnetic observatories. The Operations Committee handles applications for membership of INTERMAGNET, implements updates to the technical manual. and oversees the maintenance of standards and the annual publication of data. Intermagnet operational standards and other technical information are summarized in the technical manual.
Data
One-minute resolution data time series are available from all IMOs : these are described as "definitive data", as they are not subject to future reprocessing or re-calibration and therefore represent INTERMAGNET's "gold-standard" data product for scientific and other uses. Definitive data are therefore considered an accurate representation of the vector geomagnetic field and its time dependence at the location of each IMO. Reported or raw, unprocessed data are reported promptly from each observatory. The one-minute resolution data are time-stamped to the start of each minute and are derived from faster sampled data according to digital filters that accord with the technical standards for one-minute data.INTERMAGNET introduced a new set of standards for the measuring, recording and reporting of 1-second sampled data by IMOs. INTERMAGNET also introduced a category of "quasi-definitive" 1-minute data to encourage the prompt reporting of observatory data that are demonstrably "close" to "definitive data". Quasi-definitive data are intended to encourage the uptake of ground-based magnetometer data alongside the high volumes of satellite survey data, particularly for the construction and geophysical interpretation of regional and global magnetic field models.
The IMOs must send reported and adjusted data within 72 hours to geomagnetic information nodes, located in Paris, France; Edinburgh, United Kingdom; Golden, USA; Kyoto, Japan. In practise, however, many IMOs distribute their data to the GINs much more promptly.
INTERMAGNET data are available in several formats and data are published annually. Prior to 2014, definitive 1-minute data were published on CD or DVD and each IMO received a copy of all data. Until 2016 IMO data were made available on USB memory stick. For the 2016 data release and to mark 25 years of digital data, INTERMAGNET released a final USB stick containing all data published since 1991. For later years definitive data are available in digital form from the website only.