| Term: | DM |
| Definition: |
Dipole Meridian - A coordinate systemcentered at the observation point. Z axis is parallel to the Earth's dipoleaxis, positive northward. X is in the plane defined by Z and the linelinking the observation point with the Earth's center. Y is positiveeastward. See http://cdpp.cnes.fr/00428.pdf |
| Term: | DM |
| Definition: |
As with the solar magnetic system, the Z-axis of the dipole meridian system (DM) is chosen along the north magnetic dipole axis. However, the Y-axis is chosen to be perpendicular to a radius vector to the point of observation rather than the Sun. The positive Y direction is chosen to be eastwards, so that the X-axis is directed outwards from the dipole. This is a local coordinate system, in that it varies with position, however, since the X-Z plane contains the dipole magnetic field it is quite useful. |