Diapositive 1

1
nfce waves in the plasmasphere region  A new
observation using WHISPER/CLUSTER instrument F.
El-Lemdani Mazouz (1,2), P. M. E. Décréau (1), J.
L. Rauch (1), J. G. Trotignon (1), X Vallières
(1), S. Kougblenou (1), P. Canu (2), F. Darrouzet
(3). (1) LPC2E, ( France), (2) LPP ( France),
(3)IASB-BIRA, (BELGIUM). Email
mazouz_at_cnrs-orleans.fr
AbstractWhisper instrument on board CLUSTER
spacecraft allows the detection of a new class of
wave observation in the plasmasphere region. We
present here, spectral and statistical properties
of these observations observed at nfce, at
frequencies higher than the local plasma
frequency. We start via an event study to
present spectral properties of these
observations, frequency and intensity behaviour
are determined. High values of the modulation
index, and intensity dependence on the B field
orientation indicates a linear polarization on
the spin plan. We present also a statistical
study, on the nfce events, using a data set
covering the three years 2002-2004. Strong MLT
dependence of these emissions is shown. The
correlation between these observations and a
particular form of the plasmasphere so called
Christmas tree form is pointed out. Finally the
study of the variation of the Ae index indicates
an augmentation of this index one day before the
events, indicating a correlation between
injection of energetic particles and the
observation of nfce emissions.
A New class of wave observation nfce emissions
C4 20040317
60
80
SM coordinates
50
5 fce
60
40
dB above 10-7VrmsHz-1/2
30
40
Frequency (kHz)
20
20
10
2
0
0
2050 4.60 -23.50 22.94
2214 4.13 31.05 23.63
2111 4.36 -11.12 23.09
2132 4.43 2.38 23.25
2153 4.11 15.62 23.42
UT R(Re) LATSM() MLT
Position of the satellites at 21h10
Time frequency dependence
M7

• WHISPER new observation
• - Narrow band observation
• - Harmonic form
• - Northern and in the southern hemisphere
• - Regular plasmasphere  Christmas Tree 

• Method of the maxima of intensity
• - Exactly situated at nfce
• - Successive observation on each band
• - 3 harmonics in the NH M7,M6,M5
• Predicted by Farrel (2001)

M6
M5
Statistical properties
Orientation / Magnetic Field
Occurrence of nfce observation

• 3 years of data 2002-2004
• 30 events (C3 observation) 8

• Strongly confined to the
• premidnight
  sector

20040317
Equatorial L-MLT projection on Sm coordinates
Variation of T (angle between electric and
magnetif field)

• High values of fp
• Typical values of the
•  Christmas Tree form 

Linear polarisation observed in the spin plane

• Modulation about 90

Equatorial values of the plasma frequency

• Maximum of intensity for the higher harmonic M7
  (3.10-4 Vrms.Hz-1/2 )

nfce observations

• Maximum of intensity in the perpendicular
  direction /B

• High values of the Ae index
• 24 hours before the observation

• Conclusion
• WHISPER instrument allows the detection of a new
  class of wave phenomena at nfce, predicted
  by a maser synchrotron theory (Farrel, 2001).
• nfce observation rare phenomena strongly
  confined to premidnight sector
• Statistical and events study shown the
  relationship between this observation and the
  plasmasphere Christmas-tree form.
• MLT localization and AE index variation shown
  the correlation between nfce observation and
  particle injection.
• Mode observation in the perpendicular direction
  / magnetic field

• Particule injection

t
t-24
Noon
12
09
15
ALL perigee pass
2 3 4 5 6 L(RE)
Dawn
06
Dusk
18
Plasmapause
03
21
nfce
00
Midnight
t
t-24
Variations of the AE index in the 24 hours
preceding an observation