Download Modelling of the turbulent plasma sheet during quiet and disturbed

Ubatuba, Brazil, 4-11 October, 2009
Modelling of the turbulent
plasma sheet during quiet and
disturbed geomagnetic
conditions
M. Stepanova(1), E. E. Antonova(1, 2), J.M. Bosqued (3)
(1) University of Santiago de Chile ([email protected])
(2) Skobeltsyn Institute of Nuclear Physics, MSU ([email protected])
(3) CESR/CNRS, Toulouse, France ([email protected])
Summary
• Importance of turbulence
• Statistical studies of
turbulence in the plasma
sheet
• Case study of the turbulent
plasma sheet stability
If Re>>1 the
turbulent wake is
formed under the
obstakle.
Magnetospheric tail can be
considered as a turbulent wake
under the obstacle formed under
the conditions of very high
values of Reynolds number
(Reynolds numbers are larger
than 1010 in accordance with
Borovsky and Funsten, 2003).
Such turbulent wake is formed
even in case of laminar solar
wind flow.
V  i   V  V  i  k   V 


  
 V  i   V 
N
AV
i 1
2
N
i 1
Vrms  auto
D
2
2
Borovsky, J.E. (1997, …)
Antonova and Ovchinnikov (1997)
Stepanova et al. (2008)
  kT
V  i 1V  i  / N
N
A    exp   /  auto 
 V 
N
Vrms 
i 1
N
V

2
Velocity and magnetic field fluctuations are studied by Angelopoulos et
al. (1992, 1993, 1996, 1999); Borovsky et al. (1997, 1998), Antonova et
al. (2000, 2002); Ovchinnikov et al. (2002), Neagu et al. (2001, 2002);
Troshichev et al. (2001, 2002); Petrukovich and Yermolaev (2002);
Borovsky and Funsten (2003a,b); Voros et al. (2003); Volwerk et al.
(2004); Goldstein (2005); Weygand et al. (2005); Stepanova et al.
(2005, 2009) etc.
ISEE-2 results
(Angelopoulos et al., 1993)
CLUSTER results
Interball/Tail probe results
(Antonova et al., 2000, 2002) (Volwerk et al., 2004)
Statistical studies of eddy diffusion coefficients using the Interball/Tail satellite
Density
0.1  10cm 3
Ion temperature
 0.3keV
Mean velocity
 100km/ s
The interaction of large an
medium-scale harmonics gives
the possibility to explain the
existence of the pressure
balance across the plasma
sheet/tail lobes supported by
many measurements
(Michalov et al. [1968], Stiles
[1978], Spence et al. [1989],
Tsyganenko [1990],
Baumjohann et al. [1990],
Kistler et al. [1993],
Petrukovich [1999],
Tsyganenko and Mukai
[2003]) in spite of the
observed turbulence.
Antonova and Ovchinnikpv [1996, 1999, 2003] model
J  nV  Dn  0,
IMF Bz<-4 нТ
 j B  p,
T  const
IMF Bz>+4
The regular plasma transport related to the regular dawn-dusk electric field
acrossthe plasma sheet is compensated by the eddy diffusion turbulent transport.
It is possible to explain the bifurcation of plasma sheet when IMF Bz<0
and theta-aurora formation
Huang et al. [1987]
Frank et al. [1986]
Antonova and Ovchinnikpv [1999, 2003]
September 12, 2004 event: Cluster satellite mission
FGM – fluxgate magnetometer, three components
of geomagnetic field
CIS - Cluster Ion Spectroscopy experiment, three
components of bulk velocity, number density and
temperature.
Main goal: Study of quiet time plasma sheet
turbulence, in particular the variation of the eddy
diffusion coefficients across the plasma sheet
September 12, 2004. Really quiet time event. OMNI 1 minute resolution.
Resume:
Quiet time event,
September 12, 2004
Doy 256
1. Dst>-20 nT
2. AL>-30 nT
3. Bz>0 nT
4. Vsw<280 km/s
Thanks to IMAGE Extreme Ultra Violet (EUV) experiment - Bill Sandel (U/Arizona)
Cluster 4 measurements
Total width of the plasma
sheet – 6 Re
Typical value of the Dzz 105 km2/s
Down Dusk potential drop - 40 kV
Conclusions
• Plasma sheet is turbulent even during
quiet geomagnetic conditions.
• The level of turbulence depends on the
position in the plasma sheet
• Observed Eddy diffusion coefficients are
consistent with the observed thickness of
the plasma sheet