ipels, 29 june-3 july, 2003 whitefish, montana, usa

A. Vaivads, M. AndrA. Vaivads, M. Andréé, S. Buchert, N. Cornilleau-Wehrlin, , S. Buchert, N. Cornilleau-Wehrlin, A. Eriksson, A. Fazakerley, Y. Khotyaintsev, B. Lavraud, A. Eriksson, A. Fazakerley, Y. Khotyaintsev, B. Lavraud,

C. Mouikis, T. Phan, B. N. Rogers, J.-E. WahlundC. Mouikis, T. Phan, B. N. Rogers, J.-E. Wahlund

IPELS, 29 June-3 July, 2003Whitefish, Montana, USA

The small scale structure of the The small scale structure of the magnetopausemagnetopause

Current layers and waves

Swedish Institute of Space Physics

Uppsala

IPELS, Whitefish27 June 2003

Why small scales and waves?

Importance for large scale phenomena

Decoupling of particles

Energy transport

Energy conversion, particle energization

Remote or local sensing tool

Intro Cluster MP crossing E~jxB Separatrix Waves Summary


Uppsala


What we want to know?

Structure? sheet vs tubelocal vs globaldispersion relation

Transport plasma, energy (particles, Poynting flux)

Momentum equationGeneralized Ohm’s lawfree energy

Energy conversion j·E



Uppsala


Cluster and magnetopause scales



Uppsala


Cluster orbit, magnetopause crossings

Orbit in March

after Parks(1991)



Uppsala


2002-Feb-06 0810-0815UT

High latitude MP crossing

100km Cluster separation

s/c in burst mode

Magnetopause ~50 c/pi

Zoom into ~5 c/pi



Uppsala


s/c2a)p1040 29-Jun-2003 06:13:59

s/c4 s/c3s/c1

NV

ps [

cm-3

]

vnGSE

=105 [-0.76 -0.35 -0.54] km/s. dt= [0 0.19 0.72 -0.17] s.

1

2

3

4

5

b)

BN [

nT]

-10

0

10

c)B

M [

nT]

-20

0

20

d)

BL [

nT]

40

50

60

EyEx e) s/c 1

sc1

E [

mV

/m]

-40

-20

0

20

40

s/c 2f)

sc2

E [

mV

/m]

-40

-20

0

20

40

s/c 3g)

sc3

E [

mV

/m]

-40

-20

0

20

40

s/c 4h)

06-Feb-2002

sc4

E [

mV

/m]

08:11:56 08:11:57 08:11:58 08:11:59 08:12:00

-40

-20

0

20

40

Density dip ~1c/pi

Narrow current sheet (yellow) 5-10 e,e

Strongest E fields within the current sheet

Differences among s/c in E and B.



Uppsala


E [mV

/m] DS

Vps [V

]B [n

T] GSE

- 3 0- 2 0- 1 0

01 02 03 0

- 2 0

- 1 5

- 1 0

- 5

0

0 8 :11 : 4 0 0 8 :1 2 :0 0 0 8 :1 2 :2 0 - 5 0

0

5 0

0 6 -F e b -2 0 0 2



Uppsala


Generalized Ohms law and Cluster

jjpE

jjpBjBvE

t

t

d

d

2e

2e

ne

m

ne

1ne

m

ne

1)(

ne

1

II

Spin resolution, ion scales

● B, E, n, pe, v, j

High time resolution, electron scales

● B, E, n (fpe)

● n (satellite potential), pe, j (curlometer, 1 s/c methods)

• v



Uppsala


5-10 e,e current sheet,jperp and jII

B and n gradients coincides

E~j x B

pe not important

e- beam carrying jII can generate waves



Uppsala


E~j x B, all 4 s/c

Potential drop across the current sheet of a few 100 V

p1039 29-Jun-2003 11:56:32

s/c4a) s/c1 s/c2 s/c3

s/c4. vMP

=105 [-0.76 -0.35 -0.54] km/s GSE, Te=150eV. E low pass filtered at 30 HzN - normal to MP, towards MSh, L - closest to the mean direction of B, M=LxN. dt= [0 0.19 0.72 -0.17] s.

1

2

3

4

5

s/c 1b)

s/c1

, E

[m

V/m

]

-40

-20

0

20

EjxB/ne- T

e d

x n/n

s/c 2c)

s/c2

, E

[m

V/m

]

-40

-20

0

20

EjxB/ne- T

e d

x n/n

s/c 3d)

s/c3

, E

[m

V/m

]

-40

-20

0

20

EjxB/ne- T

e d

x n/n

s/c 4e)

06-Feb-2002

s/c4

, E

[m

V/m

]

08:11:56 08:11:57 08:11:58 08:11:59 08:12:00

-40

-20

0

20

EjxB/ne- T

e d

x n/n



Uppsala


Numerical simulations of reconnection

Two fluid, reconnection with a guide field Te=0, t=0

Width of separatrix is a few c/pe

E is strong along the separatrix

E ~j x B, in most of the system

[Rogers]

n

Bz

E

-2 -1 0 1 2 c/pi

-2

-1

0

1

2



Uppsala


MP reference frame

EM>0, EN strong inside density dip

Inflow velocity ~ magnetopause velocity

Inf

7.3

Vps

[cm

-3]

0

1

2

3

4

5

n SC [

cm-3

]

08:11:56 08:11:57 08:11:58 08:11:59 08:12:00

06-Feb-2002

-200

0

200

400

600

V [

km/s

]M

PE

[mV

/m]

MP

LMN

0

10

20

30

40 LMN



Uppsala


Waves strongest in the narrow current sheet (gradient in n and B)

Broad band

Spectral peaks f~fLH

Spectral peaks f~100 Hz, ’whistlers’

Poynting flux associated to both ’whistlers’ and ’LHD’

Waves generated by gradients or electron beams?

E

B

S-0.5

0

0.5

-2

0

2

-6

-4

-2

0

0.5

1

1.5

2

2.5

NV

ps [

cm-3

]

p1035spb 29-Jun-2003 12:43:35s/c 4

a)

-50

0

50

E [

mV

/m]

DS

I

Ex Eyb)

10

100

f [H

z]

E [

(mV

/m)2

/Hz]c)

10

100

f [H

z]

B [

nT2/H

z]

d)

10

100

f [H

z]

SII [

W/m

2H

z]1

/2

e)

08:11:57.0 .5 08:11:58.0 .5

-1

0

1

2

06-Feb-2002

SII [

W s

/m2]

whistler x100 LH x10 CS x1

f)

E

n

S



Uppsala


15-35 Hz band-pass filter (LH)

ke~1

low coherence

wave transports e- across the current sheet.

D10-9 m2/s, Diffusion?



Uppsala


Diffusion at magnetopause

Treumann [2001]



Uppsala


Laboratory observations [Carter et al. 2002]

LHD waves near the low- edge low coherence no clear correlation with

reconnection rate

Studies of B and narrow current sheets in progress

MRX – magnetic reconnection experiment



Uppsala


LHD waves in laboratory vs. space

Laboratory

Space

Broadband, fmax ~ fLH

ke ~ 1

Strongest at low- edge Low coherence Fast growth rate & damping ?

The propagation direction vDe ?along MP

emax/Te ~ 5% ~ 100%

Next step - to compare current sheets and whistlers



Uppsala


Strong E (10s mV/m)within narrow current sheets ~10 c/pe

on magnetospheric side of MP

E~jxB, pe is not important

Separatrix of reconnectionOther explanations?

Strong lower hybrid drift waves and whistlers Electron transport due to LHD waves can be important only within

the current sheet D 109 m2/s, diffusion?

Comparisons with 3D numerical simulations Many more events Separatrix studies in lab

Summary

Future



Uppsala


Particle diffusion, effective collision frequency

Diffusion approximation

j

jj

n

nD

v

Effective collision frequenacy

jyjyjj

jeff nE

Vmn

qv

,

Analytically - n,v (E+dispersion relation) Observations - n (satellite potential fluctuations)

- v=ExB (for electrons)


Uppsala


Other event

EE

BB

SS||||

2001-03-02


Uppsala


Aurora vs Magnetopause

Aurora - ion scales, can go down to electron scales Auroral field lines – narrow current sheets of Region I, II current systems

strong jII, particle acceleration, wavesoften boundary phenomena (PSBL)

Infering EII from measurements of Eperp


Uppsala


Scales

Parameter Magnetosheath Magnetosphere

B,n,Te,Ti 30nT, 10cm-3, 150eV, 1keV

30nT, 1cm-3, 1keV, 10keV

Gyroradius H+ 150km, e- 1.4 km H+ 480km, e- 3.5km

Inertial length H+ 72km, e- 1.7km H+ 230km, e- 5.3km

Gyrofequency H+ 0.46Hz, e- 840Hz H+ 0.46Hz, e- 840Hz

Lower hybrid 20Hz 20Hz

Small spatial scales between ion and electron scales and smaller

a few tens of km and below

ipels, 29 june-3 july, 2003 whitefish, montana, usa

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