Title: Thanks to : S. Dubyagin, D. Sormakov, S.Apatenkov (SPbU), Y.Asano, A. Runov, W. Baumjohann, R. Nakamura, T. Zhang (IWF), A.Petrukovich (IKI), P. Louarn , J.-A. Sauvaud (CESR), A.Fazakerley, C.Owen (MSSL), T. Nagai (TITECH), T. Mukai (ISAS)
1????? ???????? ? ????????? ? ????????
?????????????? ??????? ?????
Thanks to S. Dubyagin, D. Sormakov, S.Apatenkov
(SPbU), Y.Asano, A. Runov, W. Baumjohann, R.
Nakamura, T. Zhang (IWF), A.Petrukovich (IKI),
P. Louarn , J.-A. Sauvaud (CESR), A.Fazakerley,
C.Owen (MSSL), T. Nagai (TITECH), T. Mukai
(ISAS) INTAS grant 03-51-3738
2??????? ????????????
- ??????? ???? ?????? ? ?? ???????? ????????? ???
?????? ?????????, Cluster, Geotail - ?????? ?????? INTAS (2003)
- ???????? ? ????????????? ?????????? ???????
????? (flapping motions) - ????????? ?????
- ??????????? ?? ?????? ??????? ??????????????
- ?? ???? ????? ?? ????????????? ???????. ???????
???????????? (XY GSM), - ???????? ???.?????? ???? ??????? (Bn0),
?????????? ?? ?????? Bngt0 ??? ?????????? 1d
????????????? - ??????????? ????? ??????????? ????? ???????????
???????? ??? ??????? ???????????? (flapping)
???????? ???? -
- Cluster, Geotail
3- I. ??????????????
- flapping ??????? ?????
4Data base of rapid CS crossings / Methods
- CLUSTER ?r 1800,1000, 300km
- FGM CIS data 2001, 2004, 2003
- Data set 1 (186189 events)
- Jump Bx ?Bx gt 15 nT
- Duration 30slt t lt 300 s
- No special selection of plasma properties.
- Data set 2 (57 events, reliable normals)
- Baricenter cross the neutral sheet
- Smooth crossings, similar traces at all SC,
stable timing - Good curlometer results (DivB/Curl B lt 0.3 in gt
60 of points) - Tilt determination
- 1/ MinVarAnalysis (1SC) ? n1 , n2 (j), n3
(n) in 1d CS - 2/ Current-based (4SC) nj n1 x jNS / n1
x jNS - 3/ Timing (4SC)
5Methods How accurate are tilt determinations ??
No a priori reason why MVA should work in 1D
current sheets.. Comparison of CS normal
directions determined with timing (TIM), current
(CUR) and MVA are in good agreement
(n1n2)gt0.9 ? ? lt 25o for gt80 cases
TIM/CUR, MVA is less accurate gt
Confirm local planar approximation as reasonable
starting choice.
Practical criteria for MVA in tail CS ?2 / ?3
gt 4 ????25o, (incl 75
events)
Sergeev et al., Ann.Geophys.,p. , 2006
6Example October 20, 2001 CL at -13, 12,-1 Re
Z Y
j , n NS
- Multiple NS crossings during substorm (onset
0920UT), slow flow Vx,y (passive CS), all time
inside PS (Sergeev et al.,2004 GRL) - Consistence of n determinations from T and MVA
very large tilt toward Y !! - Consistent alternating nz (see Table)
- Alternating signs jz (B,-b, etc) and nz
variations under positive jy jz ? jy
large tilts - Propagate duskward
- Large tilts, YZ Kink mode with strong folds
720040805 Cluster TC-1, Kink mode confirmed
TC-1 -10.7 -6.8 2.6
Cluster -15.4 -8.9 3.4
- Cluster Timing MVA
- Normals swinging in YZ plane
- Kinks propagating dawnward
- at V30 km/s
- 8 NS crossings, timescale 150 500 s ,
- weak substorms
- Similar phased variations of Bx (1320-15 UT)
- Cluster TC-1 ? kinks with length gt5 Re
along the tail
Zhang et al., Ann Geo, 2005
8Appearance of Flapping Structures
- SHAPE (reconstructed from probing small parts !)
-
- appear as parts of oscillation pattern or
solitary structures parts of plane not uncommon - ?Y ? AZ ? h CS
- ?1-3Re 0.5-2Re 0.2-1Re
- Large tilts of CS parts (up to 90o to nominal Z)
- Large-amplitude Nonlinear
- Structures (Waves)
- LIFETIME
Only lower estimates are
possible in examples - with slow propagation which give
- TL can be ? 5 min
5 min
9Guide- versus normal B-field components
B vector is averaged over BX
lt3nT region. a - angle between n and Z GSM
BJ/Bn
Tilted sheets possess large guide
B-field as distinct from sheets with
standard tilt.
Standard Tilted CS
Dubyagin et al., AnnGeo, 2007 subm
10Kink Propagation and Ion flows along normal
direction
- ION FLOWS (from CIS)
- Problems effect of same order of magnitude as
possible instrumental Z-offsets and errors
transient effects and changing tilts easily ruin
any correlation only Vn is available from
timing - Special subset 42 events with nT??nJ??nMVA
within 20o - RESULTS
- Plasma flows in the same direction with same
velocity along the normal - Most of flapping Kink structures can be the
structures nearly standing in the flow
Dubyagin et al., AnnGeo, 2007 subm
11Timing propagation direction velocities
VT B1
- Propagation from center to flanks,
perpendicular to magnetic field plane - Zone of mixed direction near midnight (esp.
premidnight) where X-line observations are
most frequent at substorm onset (Nagai et 1998)
- Propagation speeds 20-300 km/s,
- median 50 km/s
- Larger speeds near MReconnection site and in
BBFs - Propagation pattern reminds the pattern of
cross-tail average flow, could be structures
standing in the flow??? -
Runov et al., AG 2005
Sergeev et al., GRL 2004
12Occurrence of Fast CS crossings
- Geotail
- 3 years data set, 3s B-field from DARTS
- 1100 fast crossings (occurrence)
- MVA with ?2/?3gt4 and Ngt15 to get normals (480
events, for tilts study) - Results
- n3 ? 0, nY, nZ like at Cluster
? confirm YZ-kink mode - duration depends on local flows
(short during fast flows and in reconnection
regions) -
- Sergeev et al. AnnGeophys, 2006
MVA normals Dawn
Dusk
13Occurrence of Fast CS crossings, 2
- Results
- n3 ? 0, nY, nZ
? confirm kink mode - duration - short
during local fast flows) - occurrence frequency increases
downtail and in Y -5..10 Re - consistent with flankward propagation,
confirm magnetospheric origin - occurrence resemble occurrence of BBFs and MR
at substorm onsets (Nagai et al.,1998) - Sergeev et al.
AnnGeophys, 2006
14Flapping Activity Dependence
- Dependence on AE and auroral activity
- Common during substorms, but sometimes met
during quiet AE - Usually associated with auroral brightenings or
poleward arcs (PC or streamer?), but clear
one-to-one relationship occur rarely - few events with NO auroral brightenings
(all CDPS events). - Dependence on Local activity
- flapping appear within the whole range of PS
parameters - sharp crossings with large tilts and large Vz
and VT are frequently noticed near MR region, and
in BBFs (?) - Needs more (quantitative) study
- Dubyagin et al., paper IAGA2005-A-00302
15Parameters of flapping current sheets
- duration lt30 - gt300s, depends on local flows
(short in BBFs and near MR) - in the neutral sheet Bns 4 nT (1..18nT),
usually BjgtBn - curvature Earthward (closed FL-90) in CL data
set - B-curvature radius Rc 5 Lcp (Lcp -gyroradius
in BL field) - halfthickness h10 Lcp (1..20 Lcp), weak
correlation with Rc - adiabaticity parameter ? Rc BL/ (Lcp Bns)1/2
0.6 (0.2..2) -
- non-adiabatic ions - any local (density/temperature/velocity)
conditions - plasma velocity BBFs only in 25, gt60
Vplt100km/s -
Runov et al. AnnGeo, 2005, p.1391, also Shen et
al JGR, 2003, p.1168
16Summary of Flapping-related structures
- Large-amplitude Nonlinear Structures (Waves or
Solitary structures) - Very large tilts (gt45o from Z in 50 of events)
- Fast CS crossings due to kink waves with
normals rotated ?B (in YZ) - Propagated center?flanks , ion speeds 20-300
km/s, median 50km/s - Occur 10-gt30 Re, frequency increases with
distance, peaks premidnight - Associated with auroral brightenings and
substorms, exceptions exist - Ion flow includes
- Vz corresponding to up/down CS motions
- Vpn flow have same sign/magnitude as the
propagation velocity
for low speed events (?)
17Mechanisms of Flapping ?
-
- MHD effect of localized reconnection with
magnetic shear (Semenov et al.,1994, Shirataki,
Fujimoto et al 2006) - Kinetic (KH or drift) instability
(Nakagawa-Nishida, 1989, Karimabadi et al.,
2003,. ) - Standing modes in (neutral Harris) sheet (Fruit
et 2002, Volverk et al., 2003) - Eigenmodes in finite Bz current sheet
(Golovchanskaya, Maltsev, 2004) - PIC simulations of CS instability (e.g. with
real hcs, Sitnov et al 2004), association with
other instabilities (e.g. LHDI, etc) - Different initial models and parameters,
different detailness of predictions - difficult
to compare - critical issues to answer
-
- MHD or kinetic effects? Instability or
generation by reconnection? - ??? - Propagation velocity (in dHT frame) ? -typically
small - CS parameters/structures favourable for
generation? - - no obvious preference..
- Different mechanisms could be involved???
18- II. ?????????
- flapping ??????? ?????
19October 20, 2001 Oscillation amplitude and CS
structure
- Vz integration vertical PS/plasma motions
- consistent variations Vc Vp
- ?z1-2 Re
- CS structure of individual crossings, from B (z)
(Vc and average tilts used) - different shapes (single peaks, flat,
bifurcated, symm/asym, time-dependent?,) - CS scale-sizes vary between 1000 km and 4000
km - All crossings are different !
Thin embedded, Bifurcated, 1 asymmetric, etc
A B b C c D d E e
20Survey of structures , comparison to Harris
distributions
- Reconstruction of 30 suitable crossings (tilts,
coord.system, Zscales) - Identify
- central embedded sheets
- bifurcated sheets
- asymmetric sheets
- Non-Harris distributions !!
- j shape deviate from Harris
- Density and j- profiles are different, flat
density distributions - (Runov et al., AnnGeo 2006)
21Parameters of Current sheet structures
- 55 Central peak, main part of the current is
concentrated in Bxlt0.5BL, BL(B22µ0Pi)½ - Typical half-thickness of the central peak
1000 - 2000 km 3 7 Lcp, - Shoulders
- 10 Bifurcated Local minimum of the current
density at Z 0 (Bx0) - Typical half-thickness 3000 km 10 Lcp
- Thicknesses of peaks of 1000 - 2000 km
- 35 Asymmetric Off-equatorial maximum of the
current density - Typical half-thickness 1500 - 3000 km
- No big difference in parameters !
- Also - No significant differences
in ion anisotropy/ nongyrotropy
22Current sheet structures
- Are non-Harris features special for
flapping sheets only (e.g.
transient effect??) - Asano et al 2005 (GRL, L03108)
- Other approach and method (no preference to
flapping sheets) - Large tilts excluded
- Results
- Harris distributions rare !
- Central embedded sheets - 40
- Bifurcated/off-center peaks - 17
- comparable to in flapping sheet survey!
- of bifurcated sheets slightly increases during
BBFs - similar conclusion by Thompson, Kivelson et
JGR2006
Harris
?B ?B
23Inconsistence of rotB and ion currents
- Expected Ti/Tegtgt1 ? jpgtgtje and main contribution
from jp to jTOT - Observed large discrepancies
- different signs jC and jplt0, jp gt jC Implies
- electrons as main current carriers ?
- Explanation dawnward convection, implies
converging En and negative e-charge in the sheet
- (Runov et al., AnnGeo 2006)
jC n e (ltVpgt - ltVegt)
24Comparisons including electron contribution
Calibration of electron spectrometer at required
accuracy appeared to be very difficult
instrumental problem Results are yet available
only for 1 long event in 2001, Seem to be
consistent with electrons to be dominant current
carrier..
B1, nT
25CS in/near Reconnection Region
- Recent findings (CLUSTER)
- Hall B-fields and current/carriers mostly
following predictions - Thin sheets 1 c/?pi (400-800km) directly
confirmed, j 30-50 (up to 120) nA/m2 - may be very short (seconds)
- large tilts are common (!?)
- may include small FRope-like structures etc,
- entire picture sometimes looks like strong
turbulence - Nakamura et al., JGR , A11206, 2006,
- Wygant et al., JGR, 2004
jzgsm
10sec CSheet in XZ gsm plane
flapping-like?
X-15Re
26 27Discussion Z-????????? ?? 1d or 2d effect?
- ?? ???? ????? ?? ????????????? ???????
????????????, 1d ???? ??????? (Bn0), ??????????
?? ?????? Bngt0 - ??????? 1d ???????? ?????? ?????????
- ?/?z gtgt?/?x ?????? ??? BxgtgtBn ? 0
- ?Xgtgt?Z (Tail approximation) ? ?????????????
- ?(z), j(z) ???????????? ?? ?-???????????????
?X
? ???????????? (???????. flapping ??)
-?????????\??????? ???????????????? ?????
????????? (20\10\01, Nakamura et 2006),
-???????? NS-?????????? (t -? ??? ?????????-?),
-???????? ?????????? ????????? gt?????
????????? ???????? ????????????? 1-2 ????????
??????????? ????? ?
28Discussion Z-????????? ?? 1d or 2d effect?
(2)
- ? ???????????? (???????. flapping ??)
- -?????????\??????? ???????????????? ?????
- ????????? (20\10\01, Nakamura et 2006), ?????
??????? ? Z- ????????? ???????? - -???????? NS-?????????? (t -? ??? ?????????-?),
- -???????? ?????????? ?????????
- gt????? ????????? ???????? ????????????? 1-2
???????? ??????????? ????? ?
3D M?? ????????????? - YZ-kink ???????????
????? - ?????? ??????????????? ???????? ???????
???? (?? X ? Y!!) ??????? ?Y ? Z, ???????
???? - ??????? ????????? ??
??????? ???-??????? ?????????? ????????????
???????? ???????. ?? ???? 2d (??????.)
???????? ?????????? ?????????????? ??.?????
Thompson, Kivelson et al., JGR 2006
29Future work
30Curlometer and proton current comparisons
YZ plane
- Explanation requires dawnward convection (50
km/s), - implies converging En ( earthward E in NS) and
negative e-charge in the sheet - origin of dawnward convection on duskside???
inconsistent with average convection - consistent with Wygant et al JGR 2005 Cluster
event analyses but obtained in
thin electron-scale CS, charge separation near MR
as compared to relatively thick
(hfew Lcp) events in our survey (?) -
- A challenge
- to confirm this explanation by studying
electron contributions and - to understand origin/mechanisms of dawnward
convection in the sheet
Hori et al.,2000, also Kauffmann et 2001,
Asano et 2003 etc