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This study examines cusp region characteristics at various altitudes utilizing data from multiple spacecraft. Emphasizing Crooker's model of antiparallel merging, it identifies a wedge-shaped cusp that rotates with the interplanetary magnetic field (IMF). Observations reveal that energetic particles are concentrated at the edges, while the center exhibits less energetic behavior. Findings from the DMSP and Cluster missions highlight a consistent presence of small-scale cusp features and suggest the possibility of spatial rather than temporal variations in the observed phenomena. Future work will focus on expanding mid-altitude observations.
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Investigating the Cusp at Multiple Altitudes by W. Keith1, M. Goldstein1, D. Winningham2, M. Wilber3, A. Fazakerley4, H. Reme5, T. Fritz6, A. Balogh7 and N. Cornilleau-Wehrlin8 1 NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771, USA 2 Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228, USA 3 University of California, Space Science Laboratory 7450, Berkeley, CA 94720, USA 4 Mullard Space Science Lab, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK 5 CESR BP 4346, 9 Ave Colonel Roche, Cedex, Toulouse, 31029, France 6 Boston University, Ctr. Space Physics, 725 Commonwealth Ave, Boston, MA 02215, USA 7 Imperial College Space and Atmospheric Physics group, The Blackett Laboratory, London, UK 8 CETP, 10-12 Ave de Europe, Velizy, 78140, France
Crooker Antiparallel merging model results in a wedge-shaped Cusp that rotates with IMF By • Figure depicts northern polar cap (shaded) for pure (a) By and (b) - By • Edges map to neutral lines in opposite hemispheres • Most energetic particles towards the edges, least energetic in the center • Green satellite tracks will see a “double” or “V” cusp • Red satellite tracks will see normal cusp dispersion pattern
OVT plot of Cluster positions in x-z GSE plane, time-shifted to cusp crossing times • Tracks represent position from 9:30 to 10:30 UT • Crossing times indicated next to markers • Spacecraft motion is northward
Savin outer cusp region with possible satellite tracks for Cluster-1 and Cluster-3
Conclusions/Future Work • Small-scale cusp feature consistently present for large IMF By • Consistent with Crooker wedge cusp and turbulent exterior cusp • Feature present over large altitude range with consistent scaling • Cluster differences may be spatial (altitude) rather than temporal • Confirm temporal stability of the mid-altitude features • Include remaining Cluster instruments in study (especially CODIF) • Find additional mid-altitude crossings for study • Attempt simultaneous multi-altitude (Cluster/DMSP) observations