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2. New Version of the AACGM Coordinate Software
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From: Kile Baker
The Altitude Adjusted Corrected Geomagnetic Coordinate System Software
Version 1.8 of the AACGM (formerly PACE Geomagnetic Coordinates)
Description In 1988 a new magnetic coordinate system was defined for
use with the Polar Anglo-American Conjugate Experiment (PACE) radar
[Baker and Wing, JGR, 94, 9139, 1989]. The coordinate system is
identical to standard Corrected Geomagnetic Coordinates (CGM) at the
earth's surface. The important feature of the coordinate system
that was different from CGM was that all points along a magnetic
field line have the same magnetic coordinates (except for a sign
change in the latitude when going from the northern to the southern
hemisphere).
The software for implementing the transformations from geographic to
geomagnetic (and vice versa) were made available to the space
physics community and a number of groups began to use the system.
An improved version of the software was implemented by Radex, Inc.
under a contract with Phillips Laboratory [Bhavani, K, C. A. Hein,
"An Algorithm for Computing Altitude Dependent Corrected Geomagnetic
Coordinates", Phillips Lab. Tech. Report PL-T-94-2310, 1994,
ADA293967]. This version also made use of the 1990 IGRF reference
field for tracing the magnetic field lines.
A new version of the system was generated in 1996 which used the
IGRF 1995 magnetic field model for tracing the field lines. K.B.
Baker (JHU/APL) modified that version to allow users to select
either the 1990 version or the 1995 version. This modified version
was made available through the AACGM web site (URL:
http://sd-www.jhuapl.edu/RADAR/AACGM/).
The latest modification to the system provides the following
features:
1) The coordinate system has been extended from a maximum altitude
of 2000 km to a maximum altitude of 7200 km.
2) New sets of coefficients have been computed to allow the system
to be used for past epochs. The new coefficient sets define the
coordinate system based on DGRF 1975, DGRF 1980, DGRF 1985, DGRF
1990, IGRF 1995.
Accessing the Software
The current version of the software from Radex, Inc. can be obtained
by contacting Dr. Fred Rich at Phillips Laboratory, Directorate of
Geophysics, Hanscom Air Force Base, MA 01731-3010.
A slightly modified version is available from Dr. Kile Baker, Johns
Hopkins Applied Physics Laboratory, Johns Hopkins Rd., Laurel, MD
20723. This modified version provides a C interface as well as an
IDL interface and also provides routines to calculate magnetic local
time (MLT) based on the AACGM coordinates. The JHU/APL version can
be obtained through the world wide web using URL
http://sd-www.jhuapl.edu/RADAR/AACGM/. This web site also provides
documentation and help on using the coordinate system. If you have
questions about this version of the software or have problems
accessing the data contact Kile Baker (kile_baker@jhuapl.edu).