Cluster "Event" Classifications

This example of a Cluster orbit (with apogee, AP at noon) illustrates the points on the orbit which are classified as "events". The craft move northward at apogee and the sequence of events predicted for one orbit is:

AP - satellite apogee
MP_N - magnetopause intersection in the Northern hemisphere
LO_N - centre of northern lobe transition
AO_N - northern auroral oval intersection (including cusp/cleft near 12 MLT)
PE - perigee
AO_S - southern auroral oval intersection (including cusp/cleft near 12 MLT)
LO_S - centre of southern lobe transition
MP_S - magnetopause intersection in the southern hemisphere

Magnetopause locations are predicted for median interplanetary conditions. Note that when apogee is near midnight the magnetopause crossings are absent. Lobe centre times are midway in time between the auroral oval and magnetopause crossings, unless the latter do not exist, in which case lobe centre times are midway between the auroral oval intersection and apogee.

The tick marks on the orbit shown are one hour apart. Note that the craft are close to "events" near apogee for extended periods, making the configuration with your ground-based station more likely to occur at some UT. For the orbit shown with, for example, a ground-based observatory at noon in the northern auroral oval, the configuration numbers are: 21 (AP), 22 (MP_N), 23 (LO_N), 24 (AO_N), 25 (PE), 24* (AO_S), 23* (LO_S), and 22* (MP_S). See orbit plots (noon/midnight) and orbit plots (dawn/dusk) for full listings of all proposed configuration numbers.