A Telescopic and Microscopic View of a Magnetospheric Substorm on 31
March 2001: New CLUSTER Observations of the Near Magnetotail

D. N. Baker 1 (303-492-4509; daniel.baker@lasp.colorado.edu)
J. L. Burch 2 (jburch@swri.edu)
P. W. Daly 3 (daly@linmpi.mpg.de)
R. E. Ergun 1 (ree@lasp.colorado.edu)
R. Friedel 4 (friedel@lanl.gov)
T. A. Fritz 5 (fritz@bu.edu)
J.-M. Jahn 2 (jjahn@swri.edu)
D. G. Mitchell 6 (don.mitchell@jhuapl.edu)
G. E. Reeves 4 (reeves@lanl.gov)

1 LASP, University of Colorado, Boulder, CO 80309, United States
2 SouthWest Research Institute, PO Drawer 28510 , San Antonio, TX 78284,
  United States
3 Max Planck Institute, Katlenburg, Lindau D37191, Germany
4 Los Alamos National Laboratory, MS D436, Los Alamos, NM 87545, United States
5 Center for Space Physics, Boston University, Boston, MA 02215, United States
6 Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20810,
  United States

The Research with Adaptive Particle Imaging Detectors (RAPID)
experiments onboard the four CLUSTER II spacecraft measure electrons
with energies >=20 keV. On 31 March 2001 at ~0635 UT when the CLUSTER
constellation had just passed through perigee, the RAPID sensors
observed an energetic electron "injection" event associated with a
strong (AE~1200 nT) magnetospheric substorm expansion phase onset. The
CLUSTER suite of spacecraft were very near local midnight and were at ~4
RE geocentric distance. The LANL spacecraft 1991-080 located at ~20 LT
also saw a strong electron injection event at ~0630 UT and the FAST
spacecraft (~19 LT) detected a powerful set of magnetic field, electric
field, and energetic particle signatures at ~0637 UT. The energetic
neutral atom imaging experiments MENA and HENA onboard the IMAGE
spacecraft detected a prominent injection of substorm-produced ions in
the pre-midnight sector commencing at ~0650 UT. The RAPID data showed a
very clear, phased timing of the electron injection signatures at the
four separate CLUSTER locations allowing us to infer the location,
speed, and direction of the substorm injection boundary. Hence, CLUSTER
(and FAST) allow us to probe microscopic details of a powerful substorm
event while IMAGE data give us a global, telescopic view of the same
magnetospheric events. This combination is a long-sought realization of
a major magnetospheric research objective and shows the powerful new
potential role of CLUSTER.