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.