This file is comprised of the variation one minute values of the geomagnetic components X, Y and Z. These data were calculated by the Air Force Geophysics Laboratory magnetometer network during the years 1978-1983. The values are variation values and should not be used in looking at absolute values of the geomagnetic components.

The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) maintains an active database of worldwide geomagnetic observatory data to further the understanding of Earth magnetism and the Sun-Earth environment.Historically, magnetic observatories were established to monitor the secular change (variation), of the Earth's magnetic field, and this remains one of their most important functions. This generally involves absolute measurements sufficient in number to monitor instrumental drift and to produce annual means. Over 70 countries operate more than 200 observatories worldwide. The magnetic observatory data are crucial to the studies of secular change, investigations into the Earth's interior, navigation, communication, and to global modeling efforts. In addition to the continuously operating magnetic observatories, many countries make measurements at temporary magnetic stations (known as repeat stations), over a period of days every 5 - 10 years.The Earth's magnetic field is described by seven parameters. These are declination (D), inclination (I), horizontal intensity (H), vertical intensity (Z), total intensity (F) and the north (X) and east (Y) components of the horizontal intensity. By convention, declination is considered positive when measured east of north, inclination and vertical intensity positive down, X positive north, and Y positive east. The magnetic field observed on Earth is constantly changing.

The abbreviations used for observatory names are as follows: GEOMAGNETIC OBSERVATORIES Code Station Geomagnetic Latitude ABG Alibag AMS Martin de Vivie. These data present the principal magnetic storms for the month as reported by several observatories through cooperation with the International Association of Geomagnetism and Aeronomy (IAGA). These are the data formerly published in the Journal of Geophysical Research. They are now, however, grouped by the storm rather than by station. The geomagnetic latitude of the station is indicated. The beginning time is given to the hour and minute in UT. The tupe of sudden commencement, if any, together with its magnitude in each element D, H or Z is next in the format: sc = sudden commencement; sc* = small initial impulse followed by main impulse (in this case the amplitude is that of the main pulse only, neglecting the initial brief pulse); dots in these columns represent a stomr with gradual commencement; blanks indicate no data entries. Signs of amplitudes of D and Z are taken albegraically; D reckoned positive if toward the east and Z reckoned positive if vertically downward. In the next columns the day and the three-hour periods on that day when the K index reached its maximum are given followed by the K index value. In the next three columns the maximum ranges in D, H and Z during the storm are given. The ending time is given only to the nearest hour. This is the time of cessation of reasonably marked disturbance movements in the trace. More specifically, it is the time when the K index measure has diminished to 2 or less for a reasonable period. For each date the data are listed in north-to-south geomagnetic latitude order.

The Space Environment Monitor (SEM) Magnetometer (MAG) instrument onboard the GOES satellite series measures the magnitude and direction of the Earth's ambient magnetic field in geosynchronous orbit. This data collection includes Reprocessed Level-1b and Level-2 SEM/MAG data from GOES 8-15. The data are enhanced to science quality from the original operational archive. Enhancements include the highest temporal cadence (2Hz), recomputed means, corrected calibration parameters, updated quality flagging, vector measurements in geophysically relevant coordinates, and full ephemeris information. The data were produced by NOAA’s National Centers for Environmental Information (NCEI) and archived by NOAA's Comprehensive Large Array-Data Stewardship System (CLASS).

The Deep Space Climate ObserVatoRy (DSCOVR) satellite is a NOAA operated asset at the first Lagrange (L1) point. The primary space weather instrument is the PlasMag suite. PlasMag includes a fluxgate magnetometer (MAG) that measures the local magnetic field, and a Faraday Cup (FC) that measures the solar wind bulk properties (wind speed, density and temperature). The PlasMag solar wind data are essential inputs for the forecasts and nowcasts provided to SWPC customers. The PlasMag data are also available to scientists for sensor cal/val and for research purposes. DSCOVR was launched on Feb. 11, 2015, so all data present in the Archive from earlier dates are data used for ground testing, and do not represent the space environment. DSCOVR became operational on July 27, 2016. End Of Life (EOL) is anticipated to be December 2019. NCEI plans to receive data until EOL, and will continue to archive the data in accordance with Data Center policies.

The Geomagnetic Indices Bulletin is a one page sheet containing the magnetic indices Kp, Ap, Cp, An, As, Am and the provisional aa indices. The bulletin is published monthly.

The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) receive airborne magnetic survey data from US and non-US agencies. In an effort to provide a central library for digital aeromagnetic data in the public domain, NCEI is continuing to assimilate new digital data from aeromagnetic surveys in the United States. Major contributors to this important data base include the U.S. Geological Survey, U.S. Naval Oceanographic Office, U.S. Naval Research Laboratory, Woods Hole Oceanographic Institution, the University of Texas, and the Natural Resources Canada (NRCAN). The details of these surveys are contained in an automated inventory system Geophysical Data System (GEODAS). The philosophy of exchange of data from the archive for new contributions has stimulated many organizations to transfer their data holdings to the Data Center.

Report on the status of world wide geomagnetic observatories

The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) receives magnetograms from over 200 geomagnetic observatories. The Center archives data from 1867 to the present, however the primary holdings are from 1957 to the present. The archives contain over 5,000 reels of 35 mm microfilm copies of magnetograms. Magnetograms are records obtained from an instrument known as a magnetometer which is designed to measure small variations in the components of the geomagnetic field. There are two types of magnetometers, the La Cour and the Ruska. The magnetogram consists of one or more (usually 3) variometers, one for each element usually D, H, Z (less common X, Y, Z) and a recorder. The standard magnetogram usually has all three components recorded simultaneously on one sheet of paper. In addition to the 3 traces, reference lines (baselines) are recorded. The baselines are used in absolute calibration of the magnetogram. The normal recording speed is 20 mm/hour with the drum turning once in 24 hours.

PC is an index for magnetic activity in the (P)olar (C)ap. It is based on data from a single nearpole station, and aimed to monitor the polar cap magnetic activity generated by such solar wind parameters as the southward component of the interplanetary magnetic field (IMF), the azimuthal component of the IMF (By), and the solar wind velocity v. The station Thule, located in the village Qaanaaq in Greenland at 86.5 degrees geomagnetic invariant latitude, fulfills the requirement of being close to the magnetic pole in the northern hemisphere. The station Vostok at 83.3 degrees does the same in the southern hemisphere. The PC index is derived independently for these two stations. The PC-index is based on an idea by Troshichev et al. (1979) and developed in papers by Troshichev and Andrezem (1985), ennerstrom et al. (1991). Earlier data for 1975-1982 appear in Troshichev et al. (1991). The data from 1975 to the present are published in Report UAG-103, available from the NOAA National Centers for Environmental Information (formerly National Geophysical Data Center).