O. Le Contel1, A. Roux 1, P. Robert1, C. Jacquey2, M. Berthomier1, T. Chust1, B. Grison1, V. Gnot2,

1
Jan. 29, 2008 substorm event (0200-0350
UT) Waves/particles

• O. Le Contel(1), A. Roux (1), P. Robert(1), C.
  Jacquey(2), M. Berthomier(1), T. Chust(1), B.
  Grison(1), V. Génot(2), J.-A. Sauvaud(2), P.
  Louarn(2), G. Fruit(2), B. Lavraud(2), V.
  Angelopoulos(3), D. Sibeck(4),C. Chaston(5), C.
  Cully(6), R. Ergun(6), J. Bonnell(5), J. Mc
  Fadden(5), K.-H. Glassmeier(7), U. Auster(7), C.
  Carlson(5), D. Larson(5), S. Mende(5), H.
  Frey(5), C. T. Russell(3), E. Donovan(8), I.
  Mann(9), H. Singer(10)

(1) CETP, CNRS/UVSQ/UPMC, France (2) CESR, CNRS,
France (3) IGPP, UCLA, USA (4) GSFC, NASA,
USA (5) SSL, UCB, USA, (6) LASP, CU, USA (7)
TUBS, Germany (8) University of Calgary,
Canada (9) University of Alberta, Canada (10)
NOAA/SEC, Colorado, USA
2
Locations in GSM 0200-0350 UT
3
Overview in GSM

• 4 dipolarisations
• N3 (Main substorm) observed first
• on Thd considering the start of
• the increase of the energetic ion
• pressure
• (cf. C. Jacquey)
• 0222 UT
• 023720 UT
• 025011 UT (Main substorm)
• 030517 UT
• Vx gt 0 Earthward flow in average
• Vy lt 0 in some cases
• Signatures on ion density on Thb
• and Thc can be observed before
• near-earth dipolarisation

4
3
2
1
4
Thc, X - 20 RE, 0200-3300 UT
Thc in the mid tail

• ? Filter banks data
• Small magnetic activity and electric activity in
  the mid-tail related to 1, 2
• No electromagnetic activity for the
• main substorm (event 3) and event 4.
• ? Density variations suggest vertical motions
  or/and thickness variations of the current sheet
• Ion velocity variations notably changes of sign
  have to be analysed from distribution functions
• - beam like structures at high and low energy
• - Boundary motion
• PS ? Lobe

5
Thd, X - 10 RE, 0200-3300 UT
Thd near-earth s/c
? Filter banks data Strong magnetic and electric
activity around 3 Hz, 12 Hz, 48 Hz The
electromagnetic activity starts after the start
of the increase of the energetic ion pressure ?
local activity associated with the local
dipolarisation ? Accelerated electrons
6
Zoom Thd, X - 10 RE 0220-0232 UT
Thd Electromagnetic and electrostatic
emissions in the range 3Hz-12 Hz during
dipolarisation Accelerated electrons
7
Thd, particle burst 0216-0235 UT
Dipolarisation
Vx,i,e gt 0 Earthward
Vy,i lt 0 Vy,e ltlt 0 Jy gt 0 and ? e-
heating Whistler emissions?
8
Thd, particle burst 0224-0228 UT
Whistler emissions Right-hand
circularly Polarised Degree of polarisation
1 Angle of propagation 0 Ellipticity
1 Helicity 1
Emissions during and after the local
dipolarisation
9
The, particle burst 0224-0228 UT
Whistler emissions Right-hand circularly
Polarised Degree of polarisation 1 Angle
of propagation 0 Ellipticity 1 Helicity
1
Emissions before and during the local
dipolarisation
Début dipolarisation sur Thd
10
The data in GSM 0224-0228 UT
Bz
Preliminary calculations Of the Poynting vector
e-
Ne
?E.B0 0 assumed ?E and ?B low-pass Filtered
below 10 Hz S (?Ex?B)/mu0 Sz gt 0 ? S
gt0 Away from the equator Source very localized
Ve
Te
?E
?B
S
S_mfa
11
Zoom 0225-0226 UT
?E 0.3 mV/m ?B 0.2 nT ?E/?B 1500 km/s S
5.e-8 -1.e-7 W/m2 Fce 424 Hz (15 nT) Fci
0.23 Hz k2c2/?2 ?2pe/(?ce?) (Helliwell,
1965) Or ?/(k vA) (?/?ci)1/2 10-14 For f
20 - 50 Hz VA 375 km/s (n01. p/cm3)
12
The data ESA e- data
13
August 17, 2003 event (Le Contel et al., ICS8)
(1654 1703 UT)

• STAFF-SC (burst mode, 450 s/s)
• Wave Polarisation 0.35-180 Hz
• ? Waves between 40 Hz to 180 Hz
• have a right-hand circular polarization
• (excentricity 0 blue color)
• ? With a wave vector parallel to B
• (? 0, blue color)
• Whistler waves ?cilt ? lt ?ce (ligtlgtle)
• (fce 400 Hz and fci 0.2 Hz for Bo 15 nT)
• k2c2/?2 ?2pe/(?ce?) (Helliwell, 1965)
• Or ?/(k vA) (?/?ci)1/2 14

14
August 17, 2003 event (Le Contel et al., ICS8)
Bx
Small scale current structure 1657-165730
Observed close to equator Bx 5 nT Large By
values -25 to -30 nT (1s) Almost same Bx, Bz
for all s/c But different By ? Parallel current
of electron scale lt 200km Observations of
whistler waves f40-180 Hz Large ?Bz(t)
oscillations - 1 nT Large ?Ey(t) - 2
mV/m ? ?E? (?)/ ?B ?(?) ? 20000 km/s 10VA On
C1, C2 and C3 but not on C4 ? propagation within
the current structure See also Stenberg et al.,
AG, 2005 about Whistler emissions close to the
magnetopause And Zhang et al., JGR, 1999
(magnetotail)
By
Bz
B
?Bz 30-180 Hz
?Ey 30-180 Hz
Vx,i,e
Vy,i,e
Jx,i,e
Jy,i,e
165730
1657
15
Summary/questions

• Small or no electromagnetic or electrostatic
  activity
• detected by mid-tail s/c
• Strong electromagnetic activity on near-earth
  s/c
• Whistler emissions before, during and after the
  local dipolarisation
• Poynting vector directed away from equator and
  earthward
• ? not so far from the source which has to
  be very localized
• Role of these whistler emissions in the substorm
  onset?
• Can we use these emissions to track the onset
  region?
• Relation of these emissions with ground-based
  observations
• To be continued