Accession Number : ADA338067

Title :   A Magnetospheric Neutral Sheet-Oriented Coordinate System for MSM and MSFM Applications

Descriptive Note : Scientific rept. no. 2

Corporate Author : BOSTON COLL CHESTNUT HILL MA INST FOR SCIENTIFIC RESEARCH

Personal Author(s) : Hilmer, R. V.

PDF Url : ADA338067

Report Date : 31 JUL 1997

Pagination or Media Count : 55

Abstract : We develop an analytic magnetospheric neutral sheet oriented coordinate system which depends on the Earth's dipole tilt angle, psi, and the geomagnetic activity index Kp. With an orientation similar to that of the GSM coordinate system, this non-orthogonal coordinate system contains coordinate surfaces (at constant Z' values) which conform to a shape approximating that of the magnetic neutral sheet. By more accurately representing a point's location relative to the magnetic neutral sheet, use of this coordinate system should help improve the current procedure used to specify geomagnetic field values and derive three-dimensional energetic particle flux information from the two-dimensional simulation results provided by the Magnetospheric Specification Model (MSM) and Magnetospheric Specification and Forecast Model (MSFM). The procedure comprises the computer codes MAP3D and FLUX3D and is limited, as are the MSM and MSFM, by use of the approximation in the magnetic field configurations which fixes the dipole tilt angle equal to zero degrees. Under this condition, all magnetic field configurations are symmetric about the GSM equatorial plane which coincides with both the model simulation surface and the neutral sheet. When input is given in GSM coordinates, the MAP3D procedure pairs off-equatorial locations with inappropriate magnetic mapping points on the MSM/MSFM simulation surface owing to the actual psi and Kp dependence of the magnetic neutral sheet position. It is suggested that improved magnetic field mapping, and thus improved specification of particle fluxes and magnetic field values, will result if all spatial points input to the MAP3D algorithm are expressed in terms of this new coordinate system rather than in GSM coordinates.

Descriptors :   *GEOMAGNETISM, *MAGNETOSPHERE, MAGNETIC FIELDS, SPECIFICATIONS, COORDINATES, DIPOLES, MAPPING, TILT, PARTICLE FLUX.

Subject Categories : Atmospheric Physics
      Geomagnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE