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

THEMIS SWT, UCLA April 9-11, 2008

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)

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

(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


Overview in GSM

4 dipolarisations:N°3 (Main substorm) observed first on Thd considering the start ofthe increase of the energetic ion pressure(cf. C. Jacquey):

1) 0222 UT2) 023720 UT3) 025011 UT (Main substorm)4) 030517 UT Vx > 0 Earthward flow in averageVy < 0 in some cases …Signatures on ion density on Thb and Thc can be observed before near-earth dipolarisation

1 2 3 4


Thc, X~ - 20 RE, 0200-3300 UT

Thc in the mid tail

Filter banks dataSmall 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 motionPS Lobe


Thd, X~ - 10 RE, 0200-3300 UT

Filter banks dataStrong 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

Thd near-earth s/c


Zoom Thd, X ~ - 10 RE : 0220-0232 UT

Thd Electromagnetic and electrostatic

emissions in the range3Hz-12 Hz

during dipolarisation

Accelerated electrons


Thd, particle burst : 0216-0235 UT

Dipolarisation

Vx,i,e > 0 Earthward

Vy,i < 0Vy,e << 0Jy > 0 and e- heatingWhistler emissions?


Thd, particle burst : 0224-0228 UT

Whistler emissions:

Right-hand circularlyPolarised

Degree of polarisation ~ 1

Angle of propagation ~ 0

Ellipticity ~ + 1

Helicity ~1

Emissions during and after the local dipolarisation


The, particle burst : 0224-0228 UT

Emissions before and during the local dipolarisation

Début dipolarisation sur Thd

Whistler emissions:

Right-hand circularly Polarised

Degree of polarisation ~ 1

Angle of propagation ~ 0

Ellipticity ~ + 1

Helicity ~1


The data in GSM 0224-0228 UT

Preliminary calculationsOf the Poynting vector

E.B0 = 0 assumedE and B low-pass Filtered below 10 Hz

S = (ExB)/mu0Sz > 0 S|| >0

Away from the equatorSource very localized

Bz

e-

Ne

Ve

Te

E

B

S

S_mfa


Zoom 0225-0226 UT

E ~ 0.3 mV/mB ~ 0.2 nTE/B ~ 1500 km/s

S ~ 5.e-8 -1.e-7 W/m2

Fce ~ 424 Hz (15 nT)Fci ~ 0.23 Hzk||2c2/2 = 2pe/(ce) (Helliwell, 1965)Or /(k ||vA) ~ (/ci)1/2 ~ 10-14For f ~20 - 50 Hz VA ~ 375 km/s (n0~1. p/cm3)


The data ESA e- data


August 17, 2003 event(Le Contel et al., ICS8)

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 = 2

pe/(ce) (Helliwell, 1965)

Or /(k ||vA) ~ (/ci)1/2 ~ 14

(1654 – 1703 UT)


August 17, 2003 event(Le Contel et al., ICS8)

Small scale current structure : 1657-165730

Observed close to equator |Bx| ~ 5 nTLarge By values ~ -25 to -30 nT (1s)Almost same Bx, Bz for all s/cBut 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 aboutWhistler emissions close to the magnetopauseAnd Zhang et al., JGR, 1999 (magnetotail)

Bx

By

Bz

B

Vx,i,e

Vy,i,e

Jy,i,e

Jx,i,e

Ey 30-180 Hz

1657301657

Bz 30-180 Hz


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 observationsTo be continued

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

Documents

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