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    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.

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    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.

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    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.

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    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.

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    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 2013 to December 2013. 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.

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    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.

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    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.

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    Hourly and minute means of the geomagnetic field vector components from observatories around the world from, respectively, 1883 and 1969, to the present day. At present there are about 160 observatories. These data are useful for tracking changes in the magnetic field generated inside and outside the Earth. Data are produced by a number of organisations around the world, including BGS. Data are available in plain text from www.wdc.bgs.ac.uk.

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    Digital hourly mean values of the Geomagnetic field elements from Lerwick, Eskdalemuir, Abinger and Hartland Observatories. Eskdalemuir data are available from 1911, Lerwick from 1926, Hartland from 1957 and all three are available up to yesterday's date. Values from Abinger (1926-1956) are available on request. Most data are definitive, but recent data (within the last 203 years) are provisional and may be corrected in the future. Values of declination (D), horizontal intensity (H) and vertical intensity (Z) are available. The units of declination are degrees. Declination is negative when west of true north. The units of horizontal intensity and vertical intensity are nT (nanotesla). Vertical intensity is positive in the downwards direction. The data from these observatories will not only aid scientific research into rates of change of the magnetic field and increase the accuracy of the BGS Global Geomagnetic Model, but will also provide data to exploration geophysicists engaged in current and future oil exploration.

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    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 2015 to December 2015. 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.