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Geomagnetism and Space Physics Program
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Danish Meteorological Institute Geomagnetism and Space Physics Program |
Contents
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DMI collaborates with SuperMAG in pursuing the common interest of making processed ground-based magnetometer data and value-added products available to the scientific community. In order to gain easy access to graphical representations of archived data from many high-latitude magnetometer networks you may visit the SuperMAG web site by clicking on the SuperMAG logo on the left. |
List of Greenland Magnetometer Stations
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geographic corrected approx.
observatory (+) alternative or IAGA (geocentric) geomagnetic MLT noon
station name former names code Lat. Long. Lat. Long. UT(hh:mm)
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Greenland West Coast (DMI)
Qaanaaq + Thule THL 77.47 290.77 84.97 29.68 15:10
Savissivik SVS 76.02 294.90 83.24 33.04 14:56
Kullorsuaq KUV 74.57 302.82 80.87 42.03 14:17
Upernavik UPN 72.78 303.85 79.12 40.01 14:25
Uummannaq Umanaq UMQ 70.68 307.87 76.53 42.26 14:15
Qeqertarsuaq + Godhavn GDH 69.25 306.47 75.40 38.93 14:29
Attu ATU 67.93 306.43 74.13 37.71 14:35
Kangerlussuaq Sondre Stromfjord STF 67.02 309.28 72.74 40.51 14:23
Maniitsoq Sukkertoppen SKT 65.42 307.10 71.55 36.87 14:39
Nuuk Godthab GHB 64.17 308.27 70.11 37.50 14:36
Paamiut Frederikshab FHB 62.00 310.32 67.56 38.72 14:30
Narsarsuaq + NAQ 61.16 314.56 65.85 42.97 14:11
Greenland East Coast (DMI)
Nord Nord NRD 81.60 343.33 81.11 103.14 9:29
Danmarkshavn DMH 76.77 341.37 77.27 85.00 10:49
Daneborg DNB 74.30 339.78 75.13 78.64 11:18
Ittoqqortoormiit Scoresbysund SCO 70.48 338.03 71.50 71.73 11:50
Tasiilaq Ammassalik AMK 65.60 322.37 68.99 53.39 13:21
Greenland Ice Cap (SPRL)
MAGIC-1 North * MCN 73.93 322.38 77.51 65.56 12:23
MAGIC-1 East * MCE 72.40 326.10 75.47 66.07 12:20
MAGIC-1 West * MCW 72.00 317.41 76.57 57.02 13:05
MAGIC-1 GISP * Summit MCG 72.57 321.55 76.39 62.14 12:40
MAGIC-2 GISP Summit MCG 72.60 321.65 76.13 60.11 12:50
MAGIC-2 Raven DYB,DYE2,PITTS MCR 66.48 313.71 71.42 45.19 14:01
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The corrected geomagnetic (CGM) coordinates are given here for the Earth's surface (altitude 0 km) and Epoch 2005.0 (* Epoch 1997.0). The approximate magnetic local time (MLT) is calculated using the North CGM Pole at geocentric latitude 82.05°N and longitude 277.10°E as a reference (Epoch 2005.0); that means the MLT Noon in UT listed here is not changing with season (see CGM Home Page for details).
Map of Greenland Magnetometer Sites
Brief Description of Greenland Magnetometers![[Map]](greenland_map.png)
DMI has acquired Greenland coastal magnetometer data in digital form since 1981. The stations listed in the table above and shown on the map were practically continuously in operation since that time, except for downtime due to equipment failure, sensor malfunction, electric power interruption, relocation of a sensor etc. From 1981 through 1990 all stations recorded with 1-min sampling rate. In 1986 DMI began to gradually modify the acquisition systems in order to record with 20-s sampling rate. Modification was completed by 1991, and since then all stations run at 20-s sampling rate. In 1999 DMI developed a further improvement od the system and changed the acquisition system to be capable to record at 1-s sampling in addition to the continued 20-s sampoling rate. In 2001 most stations were upgraded, and in the summer of 2002 the upgrade was completed.
The vast majority of the sensors now employed are three-axes linear-core fluxgate magnetometers designed and built at DMI under the supervision of Ole Rasmussen. They are optimised for long-term stability (observatory-quality instruments) rather than high sensitivity. The rms-noise is approximately 0.1 nT in the 1 mHz - 1 Hz band. During setup the sensor axes are oriented along local magnetic north (H), local magnetic east (E) and vertical down (Z). Sensors at some stations are equipped with a gimbal system which guarantees vertical alignment within a certain tilt angle range of the sensor base. The instruments run fully automatically most of the time and require (under normal conditions) no manual intervention except for changing storage media approximately once per month. A table with some magnetometer specs can be seen here.
The data acquisition system is controlled by a stable quartz oscillator which is checked against a DCF-77 reference clock about once per week at most of the west coast stations and less often on the east coast. Very modest clock slipping and frequent remote adjustment as well as regular data checks at DMI result in an overall absolute timing accuracy of better than 2 seconds in almost all cases. It should be noted, though, that the more recent data (particularly data from the present year) have not yet undergone full check and adjustment and are thus to be considered preliminary.
A few months after the end of the calendar year (typically in the spring of the following year) quiet levels (also termed reference levels) are determined for all three magnetic field components at all stations. Each daily data record is then tagged with a set of numbers representing the set of quiet levels. If no quiet level could be determined (e.g., because of jumps, significant drifts etc.), the data are flagged accordingly (in the magnetogram plots, for instance, with an asterisk next to the respective magnetometer trace).
Comparison between declination measurements from the three Greenland observatories, NAQ, GDH and THL (see map above) and IGRF model results, made over the 1981-2001 time span, revealed very good agreement between IGRF model declination and observed local declination at the observatory sites. During a survey carried out in the summer of 1990 the magnetic declination was actually measured at a number of Greenland west coast magnetometer sites. Also these data revealed satisfactory agreement with the local declination obtained from the IGRF model. To examine yourself the result of the comparison click here.
Consequently we recommend a rotation of the horizontal magnetic field around the vertical axis by the appropriate IGRF declination as the standard method for converting the magnetic variation vector from the local magnetic coordinate system into a geographic coordinate system. A further transformation into a corrected geomagnetic (CGM) coordinate system can then be made. Note that CGM and AACGM (altitude adjusted CGM) render identical coordinates for ground level locations.
Another coordinate system occasionally used - with Greenland west coast stations only - is a system where the x-axis is aligned with the best fitting great circle through all west coast stations and the y-axis is perpendicular to that great circle. The z-axis is pointing vertically down along the Earth gravity acceleration vector. The best fitting great circle intersects the geographic equator at 323.73° eastern longitude and ascends at 96.42° inclination (see the equivalent current computation section below for a graphical display).
Click here if you want to see a map of Greenland stations with geographic, best-fit great circle, local magnetic and corrected geomagnetic east-west vectors (valid for epoch 1999.0) in postscript format.
A more detailed description of the Magnetometer Array on the Greenland Ice Cap (MAGIC) is available at the University of Michigan Magnetosphere-Ionosphere Science Team (MIST) Web site.
Acknowledgment: The GEO-CGM code (v.2001) provided by NSSDC, Space Physics is used here to compute CGM latitude, oval angle and IGRF declination.
Requests for Greenland Magnetometer Data
Requests for Greenland magnetometer data and their graphical presentation are handled through the Danish Meteorological Institute (Project Scientist Dr. Hans Gleisner, hgl@dmi.dk, DMI, Copenhagen, Denmark). Any use of the data must comply with the "Rules of the Road for the use of DMI Greenland data" (see below).
1-min MAGIC data are freely available from the University of Michigan MIST (MIST) World Wide Web site. Higher resolution data (20-sec for MAGIC-1 and 10-sec for MAGIC-2) are available upon request from the project PI, Dr. C. Robert Clauer. Any use of MAGIC data must properly acknowledge NSF support for the MAGIC data acquisition.
Greenland coastal (DMI) and ice cap (SPRL) magnetometer data may be made jointly available in numerical form in various formats, see Data Distribution Details on a separate page. A request (preferably by e-mail to jfw@dmi.dk) should include a very brief description of its purpose.
The geomagnetic data acquired with the variometer stations operated by the Danish Meteorological Institute (DMI) (referred to as "data") are the intellectual property of the DMI. Data in final form may be freely used for the purpose of illustration, for teaching, and for scientific research. The DMI encourages potential users of the data to establish collaboration with the responsible scientist at the DMI with respect to the use and interpretation of the data.
Further, any user of the data must obey by the following guidelines:
Disclaimer: The data and products derived from the data are supplied without warrenties, expressed or implicit. In no event shall the DMI be held liable for any damage or loss of any kind resulting from use of the data or derived products.
Magnetogram Stack Plots (restricted access)
Data Time Span: 1981-01-01 through 2006-12-31
Acknowledgment: The GEO-CGM code (v.2001) provided by NSSDC, Space Physics is used to compute CGM latitude, oval angle and IGRF declination.
Equivalent ionospheric current modeling
This page is dedicated to the memory of the late Vladimir
("Wowa") Popov from IZMIRAN who developed this service for the benefit of the scientific community
during visits to SPRL (University of Michigan) and DMI.
A description of the technique along with a real data example can be found in the reference paper
Modeling of equivalent ionospheric currents from meridian magnetometer chain data
by V.A. Popov, V.O. Papitashvili and J.F. Watermann, Earth Planets Space,
Vol. 53, pp. 129-137, 2001.
![[Map]](greatcircle_map.png)
The map displays the best-fit great circle (black dotted line) through the Greenland west coast
magnetometer stations (blue dots). The great circle defines the reference X direction.
In order to compute the equivalent ionospheric current the observed horizontal magnetic field
is converted into components parallel and perpendicular to the great circle.
Our method estimates that component of the equivalent ionospheric current which flows
perpendicular to the great circle.
Before using our electrojet model results for presentation or to support interpretation, contact Hans Gleisner , in order to avoid pitfalls
Any use of the results produced by this technique for presentations or publications must properly acknowledge DMI and SPRL
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For questions or comments, please, contact Hans Gleisner or Vladimir Papitashvili
