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

Locations in GSM 0200-0350 UT

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 023720 UT 025011 UT (Main substorm) 030517 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

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

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

during dipolarisation Accelerated electrons Zoom Thd, X ~ - 10 RE : 0220-0232 UT Thd Electromagnetic and electrostatic emissions in the range 3Hz-12 Hz during dipolarisation Accelerated electrons

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?

Emissions during and after the local dipolarisation 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

Emissions before and during the local dipolarisation 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

Bz e- Ne E.B0 = 0 assumed Ve E and B low-pass Filtered below 10 Hz 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 > 0  S|| >0 Away from the equator Source very localized Ve Te E B S S_mfa

E ~ 0.3 mV/m B ~ 0.2 nT E/B ~ 1500 km/s S ~ 5.e-8 -1.e-7 W/m2 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 k||2c2/2 = 2pe/(ce) (Helliwell, 1965) Or /(k ||vA) ~ (/ci)1/2 ~ 10-14 For f ~20 - 50 Hz VA ~ 375 km/s (n0~1. p/cm3)

The data ESA e- data

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 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 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

 propagation within the current structure 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 < 200km Observations of whistler waves f~40-180 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

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