International Real-time Magnetic Observatory Network (INTERMAGNET) Geomagnetic Data

[Adapted from INTERNET's Data Home Page:
"http://www.intermagnet.org/Data_e.html" and Data Format Page:
"http://www.intermagnet.org/FormatData_e.html"]

INTERMAGNET data are available as magnetograms or as digital data
files. Policies and procedures for making this data available are the
responsibility of each Geomagnetic Information Node (GIN).

Preliminary data can be downloaded via your browser,
or retrieved via
e-mail. These data are generally available for the day previous to the
current one. For some of the more remote observatories, data are not
available for several days.

Definitive data in INTERMAGNET CD-ROM format can be obtained via
ftp,"ftp://www.intermagnet.org/definitive/". These data are available
for those observatories who have submitted it for inclusion in the
next CD-ROM. Older definitive data are available on the approporiate
CD-ROM.

Data Format:
The INTERMAGNET Operations Committee defines and publishes data
formats for use by INTERMAGNET participants. The data produced by
INTERMAGNET will use one of these formats:

IMF V1.22 for minute mean data.
CD-ROM for data on the CD-ROM.
IBF V1.11 for baseline data.
IAGA2002 for data in spreadsheet compatible format
IMF V2.83 for satellite transmission. (For examples of IMFV2.83
usage: "http://www.intermagnet.org/formats/V283ex_e.html".)

Due to the method that is used to record geomagnetic data it is not
possible to make continuous measurements of the absolute value of the
Earth's magnetic field. Instead a continuous record of variations in
the field is made automatically, usually using computer controlled
instrumentation. These data are made available as a preliminary data
set, called reported data. The first operation that occurs on the data
is the removal of any contamination (such as might be caused by
instrumentation faults or man-made interference). The resulting data
set is called adjusted data. This is then combined with a baseline
that has been calculated from regular spot-values of the absolute
field, which are made periodically using manual observation
techniques. The combined data set, called definitive data, is a record
of the absolute value of the field, but it is not made available until
some time after the event (typically a few months after the end of
each year).

In order to satisfy the requirements for both faster and more accurate
data, INTERMAGNET has created two separate services for data
dissemination. The INTERMAGNET CD-ROM is published annually and
contains definitive data from all participating observatories. The
Geomagnetic Information Nodes (GINs)
("http://www.intermagnet.org/Gins_e.html") provide an on-line
repository for reported and adjusted data. Data are sent from the
participating observatories to the GIN within 72 hours of
recording. They are then held on-line until the annual CD-ROM is
available.