Structure of the magnetopause boundary layers discovered by Cluster multipoint observations

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Christiana Crawford
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1 Stuctue of the magnetopause bounday layes discoveed by Cluste multipoint obsevations Hioshi Hasegawa Tokyo Institute of Technology B. U. Ö. Sonneup (Datmouth Coll.), M. Fujimoto, C. Hashimoto, T. K. M. Nakamua, K. Takagi, R. TanDokoo (Tokyo Institute of Technology), S. E. Haaland, B. Klecke, G. Paschmann (MPE), T.-D. Phan (SSL, UCB), H. Rème (CESR), A. Balogh (Impeial Coll.), M. W. Dunlop (Ruthefod Appleton Lab.), C. J. Owen (MSSL), A. Vaivads, M. Andé (Swedish Institute of Space Phys.), Y. Saito, and T. Mukai (ISAS/JAXA) (Cluste-Double Sta symposium, Sep , 2005)

2 Outline Detection of Rolled-up Kelvin-Helmholtz Votices Cluste + Realistic thee-dimensional (3D) MHD simulations Two-Dimensional Stuctue of the Magnetopause and Flux Tansfe Event (FTE) Cluste + Gad-Shafanov econstuction technique Model-based data analysis helps us a lot to intepet data obtained by the Cluste multi-spacecaft measuements.

Kelvin-Helmholtz instability (KHI) at the flank magnetopause, can

unde nothwad IMF conditions, which has been a long-standing poblem.

3 Why Kelvin-Helmholtz votices impotant? Votices, developed though the nonlinea gowth of the Kelvin-Helmholtz instability (KHI) at the flank magnetopause, can be the agent of tanspot of sola wind plasmas into the magnetosphee unde nothwad IMF conditions, which has been a long-standing poblem. (Nakamua et al., 2004) 2D simulations of KHI using 2- fluid (Hall) MHD equations including finite electon inetia

4 Plasma tanspot pocesses accompanied by the KHI gowth Magnetic econnection within a olled-up KH votex (e.g., Otto & Faifield, 2000) Collapse of votices mediated by electon inetia effects (Nakamua et al., 2004) Tubulence tiggeed though Rayleigh-Taylo instability in a olled-up votex (Matsumoto & Hoshino, 2004) Numeical simulations suggest that all these tanspot mechanisms can occu ONLY when the KHI has gown to fom Rolled-up votices.

achieved as long as the PS is thick enough (the thickness is

5 Can olled-up KH votices fom in a tail flank-like situation? Simulation esults suggest that the oll-up of KH waves can be achieved as long as the PS is thick enough (the thickness is compaable to, o lage than, the KHI wave length). (Takagi et al., 2005)

6 To what extent does the KHI gow in the actual magnetosphee? OR? Plasma tanspot can occu. Tanspot is unlikely to occu. Single- (o dual-) spacecaft measuements (e.g., Kivelson & Chen, 1995) could not answe this question. Multipoint measuements by the fou Cluste spacecaft can answe.

7 Cluste detection of Rolled-up KH votices Cluste Dusk MP South of equato Nothwad IMF Quasi-peiodic plasma & magnetic field petubations with a peiod of 2-4 min.

8 M sphee Sheath Spacecaft sepaation ~ 2000 km Density Key featues: Highe density on the most magnetosphee side (at C1) Votical flow patten

9 Evidence of plasma tanspot acoss the magnetopause Low enegy ions of sheath oigin detected thoughout Ion distibution in BL Ion distibution in sheath The obsevation is consistent with tanspot via KHI!

10 1-SC detection of Rolled-up votices possible? Diffeence between Rolled-up & Not olled-up votices y x 0 9D 15D Vx N Sheath Vx M sphee Sheath M sphee Sheath Flow speed highe than in sheath! Low density

11 Vx vs N seen in simulated data Vx High speed Low density N Sheath Vx

12 Compaison with votices obsevation MHD simulation Cluste obsevations of olled-up votices Vx N Low-density & High-speed flows ae found in eal data as well. Applicable to single-spacecaft obsevations!

13 Application to Geotail data Dusk flank MP event on Mach 24, 1995 (Fujimoto et al., 1998, Faifield et al., 2000) (X, Y, Z)~(-14, 20, 4) Re (GSM) Geotail E-T spectogam Indicato of Rolled-up votices found in 1-SC data

14 When SC sepaation of Cluste is small, Detection of a paent olled-up votex can be made by eithe of the fou spacecaft, by identifying Low-density & High-speed flows. Then, The natue of small-scale waves excited, o thin cuent sheets fomed, in the votex can be investigated in detail with the help of the multi-point measuements. Connections between maco-scale KH votices and micoscale phenomena/stuctues could be studied.

2005 Low-density issue of & High-speed Natue) flows.

15 When SC sepaation of Cluste is small, Small-scale votices discoveed in the Detection of a paent olled-up votex can be made by eithe of cusp the fou (Sundkvist, spacecaft, et al., by 11 identifying Aug Low-density issue of & High-speed Natue) flows. Then, The natue of small-scale waves excited, o thin cuent sheets fomed, in the votex can be studied in detail with the help of multi-point measuements. Connections between maco-scale KH votices and micoscale phenomena/stuctues could be studied.

16 2D stuctue of the magnetopause and FTE Gad-Shafanov econstuction technique (e.g., Hau & Sonneup, 1999) ρ V A spatial initial value poblem + ρ( V ) V = J B t Assumptions j B = p The plasma stuctue is: in a magnetohydostatic equilibium (time-independent). 2-D (invaiant along some diection, z) Gad-Shafanov (GS) equation (e.g., Stuock, 1994) 2 A 2 x B = + 2 y A 2 dp = µ 0 da t = µ 0 ( A y, A x, B ( A) z j z ), ( A) ( A = Az 2 t = ( p B z 0 P + 2µ ) A magnetic field map, A(x,y), is constucted fom explicit integation of the GS equation, using measued magnetic fields as spatial initial values. ) P

17 FTE econstuction Veification of flux ope models Sheath M sphee Flux ope size ~ 1 Re Stong coe field Evidence of component meging No econnection activity any moe Moving polewad cc = (Sonneup et al., 2004)

18 FTE Recoveed FTE Total tansvese magnetic flux within the flux ope = T. m 5 min. Reconnection E field (total magnetic flux) / (FTE occuence peiod) = (T. m) / 5 (min.) = (mv/m) ~ econnection ate = 0.04

19 Reconstuction of a magnetopause on 5 July, 2001 TD-like MP Composite map fom C1 & C4 data ~30 sec Walen plot fom C1 slope = RD-like MP Composite map fom C2 & C3 data Tempoal evolution (development of econnection) (Hasegawa et al., 2004) Walen plot fom C3 slope = 1.03

20 A futue possibility Thee is a Gad-Shafanov-type equation to descibe steam lines. Hopefully, it might become possible to econstuct a 2D map of the flow velocity field, fo example in KH votices, fom SC measuements.

21 Summay A combination of the Cluste multipoint obsevations and numeical simulations has enabled us to unambiguously detect olled-up KH votices at the flank magnetopause. The detection of the olled-up votices is now possible with a 1-SC data, poviding a possibility of studying coupling between the votices and small-scale pocesses with the Cluste data. Gad-Shafanov econstuction of magnetopause and FTE stuctues using the Cluste data demonstates time evolution of the magnetopause stuctue, and povides infomation on the appopiate FTE models, and on the natue of magnetopause econnection (the econnection ate, oientation of X-line, component meging, etc.).

23 cc = ~30 sec cc = 0.988

24 How can the seconday velocity shea be poduced? v M 1v v1 = v2 = = a v M M 2 1 a M 2v = a = a 1 M 1 leads to, 1 M 2 = M1 a M 1 v2 M2 v1 1 M M 1 2 VSEC SEC 1 1 N RATIO SEC = cuvatue adius of the 2nd velocity shea laye At a cetain adial distance fom the votex cente, the centifugal foce exeting on the low-density and dense fluids must be equal. Then, the shea velocity depends on the mass atio and on the cuvatue adius of the inteface between the two fluids.

25 0 ) + ( = nv i t n B J P dt dv n i + = = 0 γ n P dt d = B M V B M t e i e e m m M = = 1 λ n J V V i e = B J = Hall (two-fluid) MHD equations including electon inetia effects Continuity equation fo mass Momentum equation Equation of state Induction equation including finite electon inetia

26 Measuements fo an ealie inteval of the day Walen plot D-shaped ion distibution The esult suggests that econnection occued nea Cluste. This econnection might have been associated with the KHI gowth.

Magnetic Fluctuation-Induced Particle Transport. and Zonal Flow Generation in MST

Magnetic Fluctuation-Induced Paticle Tanspot and Zonal Flow Geneation in MST D.L. Bowe Weixing Ding, B.H. Deng Univesity of Califonia, Los Angeles, USA D. Caig, G. Fiksel, V. Minov, S.C. Page, J. Saff