Properties of turbulence and bursty bulk flows in the plasma sheet using the data of

THEMIS satellite mission

M.V. Stepanova1, E.E. Antonova2,3, I.L. Ovchinnikov 2, I.P. Kirpichev3, V. Pinto4, J.A. Valdivia 4

1Universidad de Santiago de Chile (USACH)2Skobeltsyn Institute for Nuclear Physics, Lomonosov Moscow State University

2Space Research Institute RAS, Moscow, Russia4Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago, Chile

Возможна ли така картина течения? (см. постер 114)

Early difficulty of the traditional approach

...A further difficulty is that the flow is probably turbulent, particulary in the "wake" of the earth, and both Pioneer I and Explorer I observations show clear indications of some hydromagnetic form of turbulence...

Dungey [1962]

Motivation:Magnetosphere as a turbulent wake

Even for laminar solar wind, the magnetospheric tail can be considered as a turbulent wake behind an obstacle, considering the very high values of Reynolds number (> 1010 [Borovsky and Funsten, 2003]).

Specific topics

• Importance of turbulence • Statistical studies of turbulence in the

plasma sheet• Study of stability of the turbulent plasma

sheet• Role of BBFs

Evidences of the turbulence in the magnetosphere

Plasma sheet turbulence was analyzed by Antonova [1985], Angelopoulos et al. [1992, 1993, 1996, 1999]; Borovsky et al. [1997, 1998], Consolini et al. [1996, 1998], Antonova et al. [2000, 2002]; Yermolaev et al. [2000], Ovchinnikov et al. [2000, 2002], Neagu et al. [2001, 2002]; Lui [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. [2005-2007]; Nagata et al. [2008], Stepanova et al. [2005, 2009, 2011a,b], Wang et al.[2010], Pinto et al. [2011] ets.

ISEE-2 results [Angelopoulos et al., 1993]

Interball/Tail probe results [Antonova et al., 2000, 2002]

CLUSTER results[Volwerk et al., 2004]

Plasma sheet turbulence in MHD models with high Reynolds number [El-Alaoui et al., 2010, 2012].

IMF Bz=-5 nT, nsw=20 cm-3, Vx=500 km/s.

How to stabilize the turbulent plasma sheet?

Existence of pressure balance across the plasma sheet/tail lobes (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 Ovchinnikov stable turbulent plasma sheet, JGR 1999

IMF Bz<-4 нТ IMF Bz>+4

Important consequences: bifurcation of the plasma sheet

under Bz>0

Koskinen et al. (2000)

Huang et al. [1987]

Frank et al. [1986]

Theory of plasma sheet with medium scale turbulence predicted the value of quasidiffusion coefficient first published by Borovsky et al. [1998] and verified by Antonova et al. [2000], Ovchinnikov et al. [2002], Troshichev et al. [2001, 2002]; Stepanova et al. [2005, 2009,2011]; Nagata et al. [2008]; Pinto et al. [2011].

Antonova et al. [2000]

The problem of space distribution of the coefficient of eddy diffusion have appeared. Spatial distribution of eddy diffusion coefficient was obtained by Nagata et al. [2008] and Wang et al. [2010]; Stepanova et al. [2005, 2009,2011]; Pinto et al. [2011]. Nagata et al. [2008]

Wang et al. [2010]

Stepanova et al. [2009] obtained value of eddy diffusion coefficient during different phases of magnetic storm using data of INTERBALL/Tail probe observations.

Variation of eddy-diffusion coefficients with the distance from the Earth, for quiet time (q), expansion (e) and recovery (r) phases of magnetic substorm .

Sharp decrease of eddy diffusion coefficient is observed at geocentric distances <10RE

Statistical studies of eddy diffusion coefficients using THEMIS mission

Stepanova et al., JGR [2011]

THEMIS results support the previous conclusions and give more information including Dxx.

The three diagonal eddy-diffusion coefficients using all THEMIS satellites were determined simultaneously from 5 till 30RE by Pinto et al. [2011]. Theory predictions obtain the additional support. Simultaneous measurements of the plasma parameters at different distances in the plasma sheet show that the diagonal components of the eddy diffusion tensor increase in the tailward direction.

Selection of intervals inside the plasma sheet

Resume:

1. Dst>-20 nT

2. AL>-30 nT

3. Bz>0 nT

4. Vsw<280 km/s

Quiet time event, September 12, 2004

Doy 256

Superdarn

Direct verification of theory using CLUSTER and radar data [Stepanova and Antonova, 2011] for September 12, 2004 event.

Averaged values of the polar cap potential difference(a), Z component of the eddy diffusion coefficient (b), the ion number density (c), and the X component of the geomagnetic field (d), in the GSE coordinate system

Variations of Bx component of the geomagnetic field (a), Vz component of the plasma bulk velocity (b), of the ion number density n (c), and temperature T (d)

Pritchett and Coroniti [2011]

Saito et al. [2008]

Magnetic holes in AMPTE/CCE data (poser 118)

Instrumentation and Data AnalysisWe used the ESA data of five THEMIS probes inside the plasma sheet. The criteria of BBFevent selection was similar to [Angelopoulos et al.(1995)]: the absolute value of the bulk velocityexceeds 100 km/s, during which the velocity exceeds 400 km/s for at least one sample period.Plasma sheet selection: XGSM < −5 Re, ZGSM < 6 Re, p > 0.01 nPa, > 0.5.QUIET: AL −100 nT, |s| 1/2 nT/min for 40 min before and after the middle of the interval.EXPANSION: AL < −100 nT s −1/2 nT/min for 5 min with respect to the middle point of theinterval, and s < 0 for 20 min with respect to the middle point of the interval.RECOVERY: AL < −100 nT and the value of the slope of the AL index was s 1/2 nT/min for 5min with respect to the middle point of the interval, and s > 0 for 20 min with respect to the middlepoint of the interval. [Stepanova et al.(2011)]

Percentage of time when the BBFs have been observed

Quiet time Expansion Recovery

Quiet time n, T, p

“Expansion” phase n, T, p

Recovery phase n, T, p

Quiet Time Flow Velocity

Expansion Phase Flow velocity

Recovery Phase Flow velocity

Conclusions

1) Plasma sheet is constantly turbulent, even under quiet geomagnetic conditions

2) The level of the turbulence depends on the geomagnetic conditions and location

3) Turbulent plasma sheet is stable due to a balance between turbulent expansion and compression by regular dawn-dusk electric field

4) BBFs appear when we need to fill urgently some parts of the magnetosphere

Cluster September 12, 2004

Very quiet geomagnetic conditions

More relaxed restriction

Stepanova and Antonova, JASTP (2011)

Instrumentation and data analysis