spase://SMWG/Instrument/Geotail/EFD

The objectives of this investigation are studies of
(1) the large scale configuration of the electric field in the magnetotail,
(2) tail electric field variations during substorms, (3) the electric
field in the plasma sheet, (4) the electric field near the magnetopause
and in the plasma mantle at locations tailward of those covered by similar
measurements on ISEE 1, (5) micropulsation and low frequency wave
measurements at frequencies covering the local gyrofrequency (.LT.1Hz) and
lower hybrid frequency (.LT.10Hz) in the tail, (6) plasma density as deduced
from measurement of the floating potential of the spacecraft, and
(7) electric field comparisons (with the aid of the other spacecraft in
the ISTP program) at different points along the same magnetic field line,
at different points along a common boundary, or in different regions of
the magnetosphere. The instrument consists of two orthogonal double probes,
each of which is a pair of separated spheres on wire booms that are
located in the satellite spin plane and whose difference of potential is
measured. The separation distances between the pair of sensors are variable
and as great as 160 m tip-to-tip. One operating mode involves length ratios
of the two antennas of about 2:1 in order to verify instrument operation
through showing that the electric field signature is proportional to the
boom length. A second reason for two pairs of wire booms in the satellite
spin plane is the requirement for measurements having a time resolution far
better than the satellite spin period.