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RECE1vr
NASA
D
STI `A
AC
CESS OEPT1Ey
NASA
Technical Memorandum 80288
Magnetic Field Studies
at Jupiter By Voyager I:
Preliminary Results
N. F. Ness, M.
01.
Acuna , R. P. Lepping,
L. F. Burlaga, K. W. Behannon, F. M. Neubauer
(NASA-TM-1302f3A)
MAGNPTIC FIF1.n STilnIES AT
479-28104
JUPIT
E
R DY VOYAGFR 1:
PRELIMINARY RF.S(ILTS
(NASA)
26 n HC A03/MF A01
CSCL OIR
!lnclas
G3/91 29944
APRIL 1979
National Aeronautics and
S
p
ace Administration
G addard Space Flight Center
Greenbelt, Maryland 20771
MAjNETIC FIELD STUDIES AT JUPITER BY VOYAGER 1:
I'MLIMINARY RESULTS
Norman F. Ness
Mario H. Acuna
Ronald P. Lepping
Leonard F. Burlaga
Kenneth W. Behannon
Goddard Space Flight Center
J reenbelt, MD
20771
a rid
Fritz M. Neubauer
Technische Universitg°t
Braunschweig, FRG
Submitted to Science:
3
April
1979
Revised:
11 April 1979
a-
Ness
-2
ABSTRACT
This paper will discuss highlights of results obtained by the
Goddard Space Flight Center magnetometers on Voyager 1 concerning the
large f;:ale configuration of the Jovian bow shock and magnetopause, and
the magnetic field
in
both the inner and outer magnetosphere. We find there
is evidence that a magnetic tail extending away from the planet on the night-
side is formed by the solar wind-Jovian field interaction. This is much like
Earth's magnetosphere but is a new configuration for Jupiter's magnetosphere
not previously considered from earlier Pioneer data. We report on the
analysis and interpretation of magnetic field perturbations associated
with intense electrical currents (approximately 5xlO
6
amps) flowing
near or in the magnetic flux tube linking Jupiter with the satellite
Io and induced by the relative
motion between lo and the co-rotating
Jovian magnetosphere. These currents may be an important source of
heating the ionosphere and interior of lo through Joule dissipation.
Ness
-3
INTRODUCTION
The Voyager magnetic field experiment consists of dual low field
(IYM) and high field (HFM) triaxial fluxgate magnetometer sensors and
ass ciated electronics with extensive redundancy for high reliability
as well as correction for the spacecraft's magnetic field (1).
One LI''M is located at
tht by
of
a 13 m.
boom while
the other is mounted
5.6
m. inboard. Total weight of sensors plus
electronics including the 2 HFM instruments is
5.6
kilograms and
the power required is 2.2 watts. During encounter, the LFMs
automatically ranged through '((of
8
possible)scales for maximum
sensitivity
(±8.8
rnanotesla (nT) to
4
6400
rnT, with quantization steps
of 0.0044 nT to 3.12 nT). The sensor equivalent RMS noise is 0.006 nT
(0.01-8.3 Fiz). The dual magnetometer method
and the est`_mation
of zero offsets yield a preliminary accuracy of +0.2 nT 4.0.1%
of full scale. The vector field was measured every
60
milliseconds,
and averages over 1.92 sec,
48
sec, and
16
min. are used in this
paper.
The present results are based upon preliminary experiment data
records (EDRs), some of which are incomplete, and
predicted
supplementary
FMs
which describe the predicted trajectory and
orientation of the spacecraft. Voyager 1 executed several
maneuvers during the encounter period which are not yet accurately
described, and these data hsve been omitted in -)ur analyses. The
experiment operated flawlessly throughout the encounter,and no
deleterious effects of the intense radiation envirrorunent and exposure
has been noted in the data processed to date