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Magnetogram Eskdalemuir 1909
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Eskdalemuir magnetogram 31/12/1909 – 01/01/1910. Source: BGS © UKRI

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BGS holds a unique collection of about 250 000 historical magnetograms on photographic paper — original recordings of the variations in the strength and direction of the Earth’s magnetic field.

The magnetogram collection — one of the longest running geomagnetic series in the world — provides a continuous record of more than 160 years of UK measurements.

Search the magnetograms collection

So what’s the attraction of magnetograms?

The collection is a valuable, partly untapped, data resource for studying geomagnetic storms, space weather and the evolution of the Earth’s magnetic field.

The magnetograms provide insight into:

  • the Earth’s outer core — long-term change (years to centuries) in the dynamo that sustains our magnetic field
  • space weather — short-term changes (seconds to days) in near Earth space and on the ground
  • space climate — long-term change (decades to centuries) in solar activity and consequences for Earth’s environment

All the above have an impact on human activities; for example, bad space weather affects technologies that we increasingly rely on, such as electrical power and GPS networks.

BGS magnetogram holdings
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Archive holdings of UK analogue magnetogram data. Source: BGS © UKRI

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Measurements from nine observatories

In the UK measurements were made at eight, long-running observatories.

We also have records from Cape Evans observatory that ran continuously at Robert Falcon Scott’s Antarctic base camp during the British Antarctic Expedition 1910–13.

Scanning the archive

In January 2009 BGS began a project to capture high quality digital images of the magnetogram collection to provide a back-up to the photographic paper originals.

The images, captured thus far, are available to search online. Scientists and the general public around the world can now gain easy access to this historical dataset.

The programme of work to complete the magnetogram digitisation is on-going and more will be added, observatory by observatory.

Information about the results of your magnetogram search

The results of your search include the Observatory name, the components used, the date range of the recording start date and a link to view the front of the magnetogram and another link to view the back of the magnetogram.

Points to note:

  1. Most of the backs of the magnetograms don’t have any data on them but we have given you the option to view them if you want just so that you know if there is anything on them or not
  2. The letters in the component(s) column are component codes. If you don’t know what they mean, view the component dictionary for an explanation. This can be accessed from the ‘See also’ menu on the right-hand-side of the brower window

Historical yearbooks

BGS also hold archived copies of the UK yearbooks.

These contain the published results from each observatory, including data manually transcribed from magnetograms, series of single or spot manual observations of the magnetic components and other derived results.

Significantly, the yearbooks provide information on the observatory operations, observing equipment and observation methods, which are essential for meaningful use of the magnetograms and other data.

Browse our online geomagnetic yearbooks and historical articles for current and past UK magnetic observatories or historic British colonial magnetic observatories (c. 1840–1850).


Contact Ellen Clarke for more information

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