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 UT

3. 4 3 2 1 Overview in GSM 4 dipolarisations:
N°3 (Main substorm) observed first
on Thd considering the start of
the increase of the energetic ion
pressure
(cf. C. Jacquey):
0222 UT UT
UT (Main substorm) UT
Vx > 0 Earthward flow in average
Vy < 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 in the mid tail Thc, X~ - 20 RE, 0200-3300 UT  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 near-earth s/c Thd, X~ - 10 RE, 0200-3300 UT  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. during dipolarisation Accelerated electrons
Zoom Thd, X ~ - 10 RE : 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 > 0
Earthward
Vy,i < 0
Vy,e << 0
Jy > 0 and 
e- heating
Whistler
emissions?

8. Emissions during and after the local dipolarisation
Thd, particle burst : 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. Emissions before and during the local dipolarisation
The, particle burst : 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. Bz e- Ne E.B0 = 0 assumed Ve E and B low-pass Filtered below 10 Hz
The data in GSM 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 > 0  S|| >0
Away from the equator
Source very localized Ve Te E B S
S_mfa

11. E ~ 0.3 mV/m B ~ 0.2 nT E/B ~ 1500 km/s S ~ 5.e-8 -1.e-7 W/m2
Zoom 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
k||2c2/2 = 2pe/(ce)
(Helliwell, 1965)
Or /(k ||vA) ~ (/ci)1/2 ~ 10-14
For f ~ Hz
VA ~ 375 km/s (n0~1. p/cm3)

12. The data
ESA e- data

13. STAFF-SC (burst mode, 450 s/s)
August 17, 2003 event
(Le Contel et al., ICS8)
(1654 – 1703 UT)
STAFF-SC (burst mode, 450 s/s)
Wave Polarisation 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 ci<  < ce (li>l>le)
(fce ~ 400 Hz and fci ~ 0.2 Hz for Bo ~ 15 nT)
k||2c2/2 = 2pe/(ce) (Helliwell, 1965)
Or /(k ||vA) ~ (/ci)1/2 ~ 14

14.  propagation within the current structure
August 17, 2003 event
(Le Contel et al., ICS8) Bx
Small scale current structure :
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 < 200km
Observations of whistler waves f~ Hz:
• Large Bz(t) oscillations ~ +- 1 nT
• Large Ey(t) ~ +- 2 mV/m
 E ()/ B ()  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 Hz
Ey Hz
Vx,i,e
Vy,i,e
Jx,i,e
Jy,i,e
165730
1657

15. Small or no electromagnetic or electrostatic activity
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