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, USA2 Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228, USA3 University of California, Space Science Laboratory 7450, Berkeley, CA 94720, USA4 Mullard Space Science Lab, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK5 CESR BP 4346, 9 Ave Colonel Roche, Cedex, Toulouse, 31029, France6 Boston University, Ctr. Space Physics, 725 Commonwealth Ave, Boston, MA 02215, USA7 Imperial College Space and Atmospheric Physics group, The Blackett Laboratory, London, UK8 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

Low-altitude DMSP “V” Cusp Crossing

High-altitude Cluster-3 “V” Cusp Crossing

High-altitude Cluster-1 turbulent “V” Cusp Crossing

Cluster 1-4, RAPID/FGM/PEACE/STAFF

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