Offprints of articles relating to Geomagnetism from 1822 to 1981. Offprints collected by Kew Observatory, Meteorological Office, Edinburgh and Greenwich Observatory (Herstmonceux castle). The first page of each offprint has been digitised to produce a finding aid.

The K-index scale summarises geomagnetic activity at an observatory by assigning a code, an integer in the range 0 to 9 (0 being the least active field and 9 the most active field) to each 3-hour Universal Time (UT) interval. K-Indices are available for Lerwick, Eskdalemuir, Greenwich, Abinger and Hartland Magnetic Observatories. From 1954-90 the values are hand scaled, from 1991 to the present day they are automatically scaled. The data not only aids scientific research into rates of change of the magnetic field and increases the accuracy of the BGS Global Geomagnetic Model, but also provides data to exploration geophysicists engaged in current and future oil exploration.

The aa index is a simple global geomagnetic activity index, with units of 1 nT (nanotesla), which is produced from the K indices from two approximately antipodal observatories. At present these are Hartland observatory in the UK and Canberra observatory in Australia. The main advantage in using aa indices for research purposes is that the time series spans further back (to 1868) than any of the other planetary indices time series.Also, up to date values are produced and made available weekly, giving nearer to real time availability than any other planetary index. In between the weekly updates, BGS calculates estimated aa indices, providing real time "nowcasts" which are updated on an hourly basis. These estimates are clearly marked with the letters "Est". Although calculated by the same method, the aa indices available on this service are not the definitive values. These are published by the International Service for Geomagnetic Indices, CRPE/CNET - CNRS, 4 Avenue de Neptune, F-94107 Saint Maur, Cedex, France.

Annual means of the geomagnetic field vector components from observatories around the world, from 1840 to the present day. At present there are about 160 observatories. These data are useful for tracking changes in the magnetic field generated inside the Earth. Data are produced by a number of organisations around the world, including BGS. Data are available in plain text from www.geomag.bgs.ac.uk. This data is connected to other geomagnetic data sets, but can be used without reference to them.

High frequency (100 Hz) data from two horizontal induction coils measuring the Earth's magnetic field at the Eskdalemuir Observatory in the United Kingdom. The data covers the period from January 2016 to December 2016. Also included are examples of Matlab code and the frequency calibration files to convert to the raw data to SI units. Thumbnail spectrograms and metadata are also supplied.

High frequency (100 Hz) data from two horizontal induction coils measuring the Earth's magnetic field at the Eskdalemuir Observatory in the United Kingdom. The data covers the period from January 2014 to December 2014. Also included are examples of Matlab code and the frequency calibration files to convert to the raw data to SI units. Thumbnail spectrograms and metadata about the setup and equipment is also supplied.

Magnetograms are used to record variations in the strength and direction of the Earth’s magnetic field. In the UK measurements were made at eight long-running observatories; Abinger, Eskdalemuir, Falmouth, Greenwich, Hartland, Kew and Lerwick. Original paper magnetograms were recorded using photographic techniques at Kew, Greenwich, Abinger, Hartland, Eskdalemuir and Lerwick Observatories. 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. These magnetograms start in the 1840s and end in 1986 at which time digital recording of the magnetic field took over and magnetograms can be produced by computer graphic. The plots show variation in the Earth's magnetic field, typically over a 24-hour period. 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. In January 2009, the 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 so 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 ongoing and more will be added, observatory by observatory.

Magnetic time-series from the BGS SWIGS differential magnetometer method (DMM) systems. Funded by NERC, grant number: NE/P017231/1 "Space Weather Impact on Ground-based Systems (SWIGS)". These data consist of measurements of the Earth’s natural magnetic field at the Whiteadder Moor remote site (WHIR) and the natural magnetic field plus the field created by GIC at the Whiteadder Moor underline site (WHIU). The database will include .xyz files with the DMM data and one document with metadata. See Hübert et al. (2020) for further details.

Magnetic time-series from the BGS SWIGS differential magnetometer method (DMM) systems. Funded by NERC, grant number: NE/P017231/1 "Space Weather Impact on Ground-based Systems (SWIGS)". These data consist of measurements of the Earth’s natural magnetic These data consist of measurements of the Earth’s natural magnetic field at the Abbey St. Bathans remote site (ASBR) and the natural magnetic field plus the field created by GIC at the Abbey St. Bathans underline site (ASBU). The database will include .xyz files with the DMM data and one document with metadata. See Hübert et al (2020) for further details.

High frequency (100 Hz) data from two horizontal induction coils measuring the Earth's magnetic field at the Eskdalemuir Observatory in the United Kingdom. The data covers the period from September 2012 to December 2012. Also included are examples of Matlab code and the frequency calibration files to convert to the raw data to SI units. Thumbnail spectrograms and metadata about the setup and equipment is also supplied.